REACTOR PHYSICS ACTIVITIES IN NEA MEMBER COUNTRIES › science › docs › 1982 ›...

- 2' NEA COMMllTEE ON REACTOR PHYSICS

REACTOR PHYSICS ACTIVITIES IN NEA MEMBER COUNTRIES

October 1981 - September 1982

OECD NUCLEAR ENERGY AGENCY 38 boulevard Suchet 75016 Paris

hEA COPWITTEE ON FEACTOR PHYSICS

FCEACTOR PHYSICS ACTIVITIES I N

LEA MEMBER COUNTRIES


OECD NUCLEAR ENERGY AGENCY 38 Boulevard Suchet , 75016 P a r i s

910400~~;.

EACTOR PEYSICS ACTIVITIES IN IVE~ . MEMBER COUNTRIES ~- ~- ~~-~ ......... ... ....

This document is a compilation of national activity reports . presented to the Twenty-Fifth Meeting of the NEA Committee on Reactor Pnysics. held at Kern?arschungszentrum Karlsruhe. F.R. of Germany. Prom 13th to 17th September 1982 .

Australia ........................................ 1

-Austria ......................................... 5 ......................................... Belgium 8 ......................................... Canada 15 ......................................... Denmark 21

Finland ......................................... 30 ......................................... France 35

F.R. Germany .................................... 44 Italy ......................................... Japan ......................................... 70

..................................... Netherlands 92 ......................................... Norway 98

Spain ......................................... 102 Sweden ........................................ 115

.................................... Switzerland 122 United Kingdom ................................. 127

+ United States of America ........................ 140

JRC. Ispra ...................................... 146 .................................... USSR (Annex) 152

REACTOR PHYSICS ACTIVITIES Ih: AUSTRALIA

(October 1981 - September 19.82)

D . B . McCULLOCH

A u s t r a l i a n Atomic Energy Commission, Lucas Heights Research L a b o r a t o r i e s , Lucas He igh t s , N.S.W., A u s t r a l i a .

1. REACTOR CODES AND DATA LIBRARIES a 1.1 Development o f AUS module, POW-3D

Development o f POW-3D, t h e 3-dimensional n e u t r o n d i f f u s i o n module of t h e AUS scheme, i s n e a r l y comple te . The code i s now b e i n g phased i n t o r e p l a c e t h e p r e v i o u s ( 2 - D ) code POW f o r even two-dimensional problems, a s it o f f e r s c o n s i d e r a b l e advantages i n performance due t o i t s s u p e r i o r numer ica l t e c h n i q u e s i n c e r t a i n key a r e a s . The code i s a l s o be ing used a s a t e s t v e h i c l e f o r c o a r s e mesh r e b a l a n c i n g t e c h - n iques implemented ove r m u l t i - g r i d s .

1 . 2 Development of AUS Modules and Data L i b r a r y f o r Fusion Blanke t C a l c u l a t i o n s

A new group c r o s s - s e c t i o n l i b r a r y f o r f u s i o n b l a n k e t s has been p repa red f o r u s e w i t h i n t h e AUS code system. P rev ious AUS l i b r a r i e s have c o n t a i n e d o n l y neu t ron c r o s s - s e c t i o n d a t a b u t t h e new l i b r a r y , AUS.ENDF200G, a l s o c o n t a i n s photon p roduc t ion and photon i n t e r a c t i o n d a t a a s w e l l a s kerma f a c t o r d a t a f o r energy d e p o s i t i o n c a l c u l a t i o n s . The number o f neu t ron groups h a s been i n c r e a s e d from 128 t o 200 by ex t end ing t h e energy range t o 15.5 MeV and u s i n g l e t h a r g y d i v i s i o n s a s f i n e a s 1/32 a t h igh e n e r g i e s . The number of photon groups i s 37. The l i b r a r y c u r r e n t l y c o n t a i n s t h e n u c l i d e s used i n f u s i o n b l a n k e t d e s i g n s p l u s some of t h e more i m p o r t a n t n u c l i d e s f o r g e n e r a l s h i e l d i n g c a l c u l a t i o n s and f i s s i o n r e a c t o r c o r e s . Uranium i s o t o p e d a t a a r e i nc luded b u t t o d a t e , n o t p lutonium. The f i s s i o n and s h i e l d i n g d a t a have been i n c l u d e d t o a s s i s t i n d a t a l i s t i n g b u t it is in t ended t h a t t h i s one l i b r a r y w i l l e v e n t u a l l y be used f o r a l l n e u t r o n i c c a l c u l a t i o n s .

The l i b r a r y has been p repa red from ENDF/B-IV u s i n g a number o f l o c a l l y w r i t t e n programs and programs o b t a i n e d from RSIC. Treatment o f n e u t r o n d a t a has been p r e v i o u s l y d e s c r i b e d . The AMPX module SMUG was used f o r photon i n t e r a c t i o n d a t a and t h e MACK I V code f o r photon p roduc t ion and neu t ron kerma d a t a . The AMPX module LAPHNGAS which has been a s t a n d a r d method of g e n e r a t i n g photon p roduc t ion d a t a was t r i e d o r i g i n a l l y b u t proved u n s a t i s f a c t o r y f o r t h e w e i g h t i n g spec t rum and l a r g e number o f t h e r m a l g roups which were used . The u s e o f MACK I V f o r photon p roduc t ion d a t a enab led t h e g e n e r a t i o n o f c o n s i s t e n t photon

produc t ion and neu t ron kerma d a t a . A n x b e r of m o d i f i c a t i o n s t o .MACK IV were r e q u i r e d . I n p a r t i c u l a r , p r o v i s i o c was made f o r v a r i o u s r e a c t i o n s t o be kep t s e p a r a t e t o a l low t h e oucput to be r eno rma l i s ed t o XLKS c r o s s - s e c t i o n s and t o a l l o w f o r resonance s h i e l d i n g .

The AUS c r o s s - s e c t i o n da t a -poo l s t r s c t u z e was g e n e r a l i s e d t o a l l ow t h e i n c l u s i o n of photon d a t a . Major mo&if icat io? .s t o t h e MIRANDA module were r e q u i r e d t o p r o c e s s t h i s d a t a . Secause it is r e a s o n a b l e f o r o t h e r modules t o work w i t h c r o s s - s e c t i o n d a t a 3001s i n which no d i s t i n c t i o n i s made between neu t ron and photon d a t a , t h e y r e c u i r e d l i t t l e modi f ica - t i o n .

2. NEACRP PWR SHIELD BZNCHNhRK PROBLEM . R e s u l t s were submi t t ed f o r t h e F e S * a c t i v a t i o n i n t h e c o r e b a r r e l

and p r e s s u r e v e s s e l c l a d d i n g , t h e n e u t r o n damage p r o d u c t i o n r a t e i n t h e p r e s s u r e v e s s e l and t h e neu t ron and gamma-ray d o s e s a t t h e o u t s i d e of t h e 155 cm t h i c k c o n c r e t e s h i e l d . The subsequent i n t e r - compar i son of r e s u l t s from t h e p a r t i c i p a t i n g l a b o r a t o r i e s has been a v a l u a b l e tes t of o u r methods f o r c a l c u l a t i n g such a s h i e l d , and o u r r e c e n t l y produced 200 neutron-37 gamma-ray group c r o s s - s e c t i o n l i b r a r y t o be used f o r f u s i o n n e u t r o n i c s s t u d i e s . An impor t an t s u b s i d i a r y f i n d i n g from p r e p a r i n g our benchnark s o l u t i o n , was t h a t t h e o l d 128 group l i b r a r y s i g n i f i c a n t l y ove re s t ima ted t h e f a s t neur ron dose a r t h e o u t s i d e of a t h i c k c o n c r e t e s h i e l d , e s p e c i a l l y i n t h e i m p o r t a n t 1-3 MeV enerqy r anae .

O v e r a l l t h e agreement w i t h workers from o t h e r L a b o r a t o r i e s i s most encourag ing . Our neu t ron r e s u l t s were w e l l w i t h i n t h e range of v a l u e s s u b m i t t e d . Our gamma-ray dose a t t h e o v t s i d e of =he s h i e l d was t h e h i g h e s t s u b m i t t e d , bu t was on ly 15 p e r c e n t above t h e nex t h i g h e s t v a l u e . Although n o t i nc luded wi th o u r submi t t ed s o l u t i o i l , t h e qamma-ray h e a t i n g i n t h e c o r e b a f f l e , t h e c o r e b a r r e l , t h e F r e s s u r e v e s s e l and a t t h e i n s i d e of t h e c o n c r e t e s h i e l d have now been c a l c v l a t e d , and a l s o a g r e e w e l l w i t h t h e v a l u e s submi t ted by o t h e r l a b o r z t o r i e s .

3. RESZARCS EACTOR PSYSICS

3 . 1 C o m ~ u t a t i o n a l models f o r HITAR n e u t r o n i c s

Because of t h e r e c u r r i n g need f o r r e a c t o r p h y s i c s c a l c n l a t i o n s o' HITAR (heavy w a t e r moderated, DIDO-type 1 0 MW r e s e a r c h r e a c t o r ) , a s t a n d a r d set o f models has been deve loped . These models i n v o l v e pro- c e d u r e s , u s i n g t h e AUS scheme, f o r c a l c u l a t i n g q u a n t i t i e s o f i n k e r e s t . f o r r e a c t o r o p e r a t i o n , s a f e t y s t u d i e s , e t c . I n p u t t o codes i s i n t h e form of c a r d image d a t a sets on d i s k , and t h e models a r e r e a d i l y a v a i l a b l e " a t c a l l " .

E a r l i e r SIFAR models i n u s e produces an a lmos t f l a t f l u x a c r o s s t h e c o r e and v e r y h igh e x c e s s r e a c t i v i t i e s . They cou ld hence n o t b e used w i t h any deg ree o f con f idence . it was found from e x t e n s i v e i n v e s t i g a t i o r z h a t t h e r e was no s i n g l e e x p l a n a t i o n f o r t h e i n a d e q u a c i e s o f t h e s e model: b u t t h a t f o r s a t i s f a c t o r y r e s u l t s it was neces sa ry t o r e p r e s e n t i n some d e t a i l many f e a t u r e s of t h e r e a c r o r , i n c l u d i n g a l l t h e r e f l e c t o r D20 f a c i l i t i e s .

The models have been bssed on BIFELR o p e r a t i o n a l program 251 which was t y p i c a l o f t h e low r i g burden HITAR o p e r a t i o n s of 1978-1975, and a r e p r e s e n t l y a v a i l a b l e a s fo l lows :

a ) BVHIFXS - t h i s i s a 5-group smeared c r o s s - s e c t i o n p r e p a r a t i o n model. Fue l c r o s s - s e c t i o n s a r e produced a s a f u n c t i o n o f burnup f o r use i n t h e models BVHIFRZ, BVHFXYA2 and BVHFXYE2 .

b ) BVHIFRZ - t h i s i s a c y l i n d r i c a l d i f f u s i o n HIFAR model. Region and energy dependent a x i a l buck l ings a r e produced f o r use i n t h e models BVHFXYA2 and BVHFXYE2.

C ) BVHFXYA2 - t h i s i s a two d imens iona l XY geometry , d i f f u s i o n model of HIFAR, w i t h average end-of-program 251 burnup th roughout t h e c o r e .

d ) BVHFXYE2 - t h i s i s a two d imens iona l XY geometry , d i f f u s i o n model of HIFAR w i t h t h e e x p l i c i t end-of- program 251 f u e l l o a d i n g s f o r each f u e l e lement .

e ) BVHIFCEL - t h i s i s an ' a v e r a g e ' f u e l c e l l c a l c u l a t i o n . The composi t ion of t h e f u e l i s t h a t of average f u e l a t t h e end-of-program 251 and i n c l u d e s f i s s i o n p r o d u c t s .

R e p r e s e n t a t i o n s o f h o r i z o n t a l and v e r t i c a l heavy w a t e r f a c i l i t i e s , vo ided s a f e t y rod t h i m b l e s and r i g s have been i n c l u d e d i n t h e models BVHFXYA2 and BVHFXYE2. The r i g r e p r e s e n t a t i o n ( accoun t ing f o r 4.23% i n r e a c t i v i t y ) was tuned t o d i r e c t r e a c t i v i t y measurements, b u t a l l o t h e r r e f l e c t o r d e t a i l ( accoun t ing f o r 3.52% i n r e a c t i v i t y ) was ca l cu - l a t e d .

The c a l c u l a t e d end-of-program r e a c t i v i t i e s of . 0 9 % and - 6 9 % f o r t h e models BVHFXYA2 and BVHFXYE2 r e s p e c t i v e l y , compare w e l l w i t h t h e OP251 observed shutdown r e a c t i v i t y o f 1 .43%. Limited comparisons w i t h expe r imen ta l f l u x e s i n d i c a t e agreement t o w i t h i n 10%. Even though t h e s e models have been developed f o r a s p e c i f i c o p e r a t i n g program, it i s expec t ed t h a t , w i t h l i t t l e o r no change, t h e y w i l l prove u s e f u l f o r any c u r r e n t o r f u t u r e o p e r a t i n g programs. They have a l r e a d y been e f f e c t i v e l y a p p l i e d i n s t u d i e s of t h e e f f e c t s on i m p o r t a n t r e a c t o r p h y s i c s and n e u t r o n i c performance pa rame te r s of r e d u c i n g t h e 2 3 5 ~

enr ichment of HIFAR f u e l .

3.2 A n a l y s i s o f r e a c t i v i t y induced power t r a n s i e n t s i n heavy w a t e r moderated, h i g h l y e n r i c h e d uranium r e s e a r c h r e a c t o r s

E f f o r t has been d i r e c t e d t o a t t a i n i n g an u n d e r s t a n d i n g o f s e l f l i m i t e d t r a n s i e n t s i n r e a c t o r s of t h e D I D O t y p e . T h i s h a s i nvo lved t h e s t u d y o f t h e n e u t r o n i c s of t h e SPERT c o r e BD22/24 and t h e u s e o f r e a c t i v i t y c o e f f i c i e n t s o b t a i n e d from t h i s work i n t h e t r a n s i e n t a n a l y s i s code ZAPP. Good agreement w i t h d a t a from t h e SPERT tests was o b t a i n e d f o r t r a n s i e n t p e r i o d s g r e a t e r t h a n 140 m s . For s h o r t e r p e r i o d s a vo id development model was r e q u i r e d t o match t h e expe r imen ta l d a t a . For an e x c u r s i o n p e r i o d o f 50 m s about h a l f t h e compensated r e a c t i v i t y was prov ided by vo id fo rma t ion . The v o i d model, which r e l i e d on a b e s t f i t t o BD22/24 d a t a gave v e r y good agreement w i t h d a t a from t h e SPERT 1 c o r e D12/25, f o r which vo id fo rma t ion becomes s i g n i f i c a n t a t much s h o r t e r p e r i o d s (-25 m s f , w i t h o u t ad jus tment t o t h e model.

The method o f c a l c u l a t i o n has been a p p l i e d t o HIFAR t o f o l l o w t h e c o u r s e of t r a n s i e n t s produced by l o s s o f a c e n t r a l c o a r s e c o n t r o l arm ( C C A ) . The c a l c u l a t i o n i n c l u d e s t h e dynamics o f t h e arm f a l l and t h e

. . t r i p f u n c t i o n r e s p o c s e , which was d i r e c ~ l y xeasc red by f e e d i n g a h y b r i d computer o u t ? u t t o a c t u a l t r i? u n i t s . I t was concluded t h a t w i t h i n t h e range of e x c e s s r e a c t i v i t i e s . p e r m i t t e d i n normai o ? e r a t i o n , t h e r e a c t o r would w i t h s t a n d t h e i n i t i z l power b u r s t 5o:lowing an arm l o s s . The t r i p f u n c t i o n ( t o i n s e r t t h e remainder of t h e CCA bar-k) i s r e q u i r e 6 o n l y t o r e t u r n t h e r e a c t o r t o a s u b c r i t i c a l s t a t e and s u p p r e s s f u r t h e r power o s c i l l a t i o n s , f o r which h i q h speed response is noz n e c e s s a r y .

=ACTOR PHYSICS ACTIVITIES I N AUSTXA

October 1981 - S e ~ t e m b e r 1982

compiled by

F. Pu tz

1. -%ACTOR THEORY

1.1 S e a c t o r Ana lys i s

Study of wa te r ' i n g r e s s a c c i d e n t s i n HTR's has cont inued

t o be an impor t an t a c t i v i t y a t ITP/TU Graz ( I n s t i t u t f u r

Theore t i s che Physik d e r Technischen U n i v e r s i t a t G r a z ) .

The purpose of t h i s s tudy i s t o f i n d o u t t o what e x t e n t

t h e code GAhlTEREX designed f o r t h e d e s i g n o f h igh tempe-

r a t u r e r e a c t o r c o r e s i s a ~ p l i c a b l e t o t h e a n a l y s i s of

such a c c i d e n t s . The c a l c u l a t e d r e s u l t s showed good

agreement w i t h r e a c t i o n r a t e s measured i n t h e SIE?IENS-

ARGONAUT r e s e a r c h r e a c t o r , t h e t e s t zone of which was

f i l l e d w i t h AVR-fuel e lements . The w a t e r i n g r e s s h a s

been s imu la t ed by f i l l i n g t h e i n t e r s p a c e between t h e

g r a p h i t e s p h e r e s w i t h a mix tu re of s m a l l po lye thy lene

and p o l y s t r o l p a r t i c l e s .

The i n v e s t i g a t i o n s c a r r i e d o u t a t GFZS ( O s t e r r e i c h i s c h e s

Forschungszentrum S e i b e r s d o r f ) j o i n t l y w i t h KFA J i i l i c h

(FRG) on t h e r e a c t i v i t y and t empera tu re c o e f f i c i e n t has

been extended t o f u e l management s t r a t e g i e s d i f f e r e n t

from t h e OTTO procedure . The code WIYS w i t h a n u c l e a r

d a t a l i b r a r y based on t h e U . K . Nuclear Data F i l e s i s

be ing used f o r t h e c a l c u l a t i o n s .

Work done a t V Z S w i t h i n t h e scope of t h e benchmark

p r o g r m e c o o r d i n a t e d by I . G A zimed a t i n v e s t i g a t i n g

t h e convers ion of r e s e a r c h an6 t e s t r e a c t o r s from

h igh-enr iched t o reduced-enr iched uranium f u e l has

been completed.

Reactor K i n e t i c s

A code c a l l e l FASTRAK has been developed a t 5FZS f o r

t h e a n a l y s i s o f r e c r i t i c a l i t y a c c i d e n t s i n f a s t r e a c -

t o r s . Th i s code i s based on a f a c t o r i z a t i o n method

and has an o p t i o n t o u s e t ime dependent f l u x shape

f a c t o r s being c a l c u l a t e d u s i n c a d i s c r e t i z a t i o n

scheme based on t h e mesh g r i d which may be d i s t o r t e d

by t h e hydrodyntmic d i s2 iacement of t h e c o r e m a t e r i a l .

Th i s method pe-mits t h e d i r e c t c a l c u l a t i o n of t h e

r e a c t i v i t y : t h e r e f o r e t h e i n t e r a c t i o n of o u t e r

r e a c t i v i t y , Doppler r e a c t i v i t y and d i s sa s sembly

r e a c t i v i t y i s c o r r e c t l y t aken i n t o account . I t was

p o s s i b l e t o show t h a t t h e i n t r o d u c t i o n of t ime depen-

d e n t f l u x shape f a c t o r s may c o n s i d e r a b l y improve t h e

r e s u l t s .

T ranspor t Theory

A s t u d y i s underway

r e t i s c h e Physik d e r

a t ITP/U 2 r a z ( I n s t i t u t f u r Theo-

U n i v e r s i t a t G r a z ) i n v e s t i g a t i n g

t h e passage of neu t ron p u l s e s through s t r a t i f i e d media

u s ing t h e method of m u l t i p l e c o l l i s i o n p r o b a b i l i t i e s .

Plasma Phys i c s

Some a s p e c t s of n e u t r a l beam h e a t i n g and plasma con-

f inement concepts a t low 2-values a r e being s t u d i e d

a t IT?/TLl Graz. E f f o r t h a s been c o n c e n t r a t e d on i n -

v e s t i g a t i o n s of t h e Soltzmann c o l l i s i o n t e r m and

energy transfer in a stationary two component plasma

as well as of the solution of the nonhomogeneous

Fokker-llanck equation. The use of Sonine polynomials

leads to a transformation of the Fokker-Planck equa-

tion into a system of ordinary differential equations

of simzle structure.

2. ZXPERIYENTAL WACTOR PHYSICS

2.1 Neutron Flux Yeasurements

The fast neutron flux density (E> 1 :lev) has been

measured in various experimental positions of the

"RIGA-:?ARK I1 reactor of A1 (Atominstitut der

rsterreichischen UniversitYten, Wien) using thres-

hold activation foils; the neutron spectra were

unfolded by means of the SAND I1 Trogramme. At the

same institute people succeeded in determining the

thermal neutron flux density by a simple SPN-detector

exposure achieving the same accuracy as with the

activation method.

2.2 Gamma Detection

For the measurement of the local gamma dose rate in

the core of a TRISA-?IARK I1 reactor self-powered

gamma detectors using Ta and W rods or hollow cylin-

ders as emittors have been developed at AI. Present

results show good gamma response of the detector

with detector sensitivities in the range of 1. lo-15A/~. h-l.

2.3 Xeasurement Technique

In order to reduce errors in the evaluation of data

gained from activation foils a computerized NaJ-radiation

measuring device combined with automatic change of

samples has been developed at ITP/TU Graz rendering

additional corrections superfluous.

=ACTOR PHYSICS ACTIVITfZS I N EELGIUM

September 7981 - August 1982

J. DEBRE (s.c.K./C.E.N., MOL)

FAST FZACTORS

C r i t i c a l exper iments --------------- The e v a l u a t i o n of t h e Y I S T experiments i n Z92A with SAXR-2 methods and

d a t a was cont inued i n c o l l a b o r a t i o n with K-CK and INTEXATOH. The c o n t r i -

bu t ion of BELG3NJCLXAI33 concerned

- t he r e l a t i v e v o r t h s of c o n t r o l rod abso rbe r s (enr iched and n a t u r a l

BqC, Eu203) i n YW and o t h e r assembl ies

- t h e f i s s i o n r a t e d i s t r i b u t i o n s i n B Z A ~

- t h e c o n t r o l rod worth measurements i 2 SZC/ I , t h e f i r s t heterogeneous

core b u i l t i n t h e B I E T programme. -

The b e l g i a n p a r t i c i p a t i o n t o t h e 2kCIhZ programme i n MASmCA, s t a r t e d i z

1980, i s mainly devoted t o t h e de te rmina t ion of t h e gamma h e a t i n g d i s t r i -

bu t ions . I n 1982, a second s e r i e s of measurements were performed i n t h e

c o n f i g u r a t i o n RACINE l A , a double-r ing heterogeneous co re , by means of

7 ~ i ~ , CaSOq and A120, thermoluminescent d o s i a e t e r s . The programme was 2

organized t o make p o s s i b l e t h e comparison with Cadarache and W i n f r i t h

r e s u l t s . Thernoluminescent dos imeters from t h e t h r e e l a b o r a t o r i e s were

a l s o exposed i n a r e f e r e n c e g a m a f i e l d ( 6 0 ~ o : a t Cadarache; t h e e x o s u r e

r a t e determined on t h e b s s i s of t h e c a l i b r a t i o n a t Xol ag rees w i th in about

3 % with t h e r e f e r e n c e value. A s i m i l a r agreement was p rev ious ly ob ta ined

i n a comparison with Harwell. I n o rde r t o reach a r ep roc iuc ib i l i t y of a

few p e r c e n t s i n r o u t i n e measurements, an i n d i v i d u a l c a l i b r a t i o n of each

dosimeter i s necessary.

An i n v e s t i g a t i o n of t h e s e n s i t i v i t y of t he rno lun inescen t gamma dos ime te r s

t o low energy neu t rons seems necessary. The f e a s i b i l i t y s tudy of a r e f e -

rence n e u t r o r and gamma f i e l d was performed, i n which t h e i n o r t a n c e of t h e

gamma f l u x with r e s p e c t t o slow neu t rons can be v a r i e d and a c c u r a t e l y c a l -

cu la ted . T ie extreme case i s t h e e q u i l i b r i u n s t a t e i n a thermal column made

of h igh p u r i t y g r a p h i t e where t h e on ly gamma c o n t r i b u t i o n i s due t o neut ron

cap tu re i n t h e medium. I n t h e s e s eve re c o n d i t i o n s , p re l imina ry measurements

revea led a much lower neutron s e n s i t i v i t y f o r A 1 0 compared t o 7 L i ~ . 2 3

Computer programmes ------------------- I n o rde r t o suppor t t h e management of t h e f u e l and c o n t r o l assembl ies of

SUTERP~FENIX 1 , t h e computer programme SUPERCAPaE i s be ing developed a t

CEA-Cadarache. Tn i s programme should p r e d i c t t h e parameters of t h e core

i n v a r i o u s s i t u a t i o n s , s t a r t i n g from a wel l -def ined r e f e r e n c e s t a t e , us ing

p r e c a l c u l a t e d parameters . BELGONUCLEAIXE c o n t r i b u t e s t o t h i s work.

The two-dimensional programmes DIAMAXT ( t r a n s p o r t , S,, developed by SCK/C3N

an.' K E K ) and T R I B U ( d i f f u s l o 2 , developed by SCK/CEN and SZLGONUCLEAWE),

which d e s c r l b e t r i a n g u l a r and hexagonal geomet r ies , were app l i ed f o r com-

p a r i s c n t o t h e c a l c u l a t i o n of t h e r e f e r e n c e homogeneous core SNR-2. Th i s

comparisor concerned k e f f , mesh s i z e e f f e c t s , power d i s t r i b u t i o n , c o n t r o l

rod worths , CPU t imes .

S a f e t y s t u d i e s -------------- Recent numerical r e s u l t s ob ta ined with CASSANDRE, a two-dimensional code f o r

f a s t r e a c t o r power excurs ions a n a l y s i s , were publ i shed [I]. Th'e code has

been run on t h e supefproapt benchmark t r a n s i e n t proposed by NEACRP ( S p e c i a l i s t s '

meeting, Garching, 1975); t h e e v o l u t i o n s of r e a c t i v i t y , power l e v e l and

temperature c a l c u l a t e d with CASSANDRE compares s a t i s f a c t o r i l y with s o l u t i o n s

from o t h e r l a b o r a t o r i e s .

The p r e p a r a t i o n of a s e r i e s of p o s t e c c i c e n t hea t removal (?AiE?) experiments

i n t h e BR2 r e a c t o r i s under p r o g r e s s [ 2 ] [ 3 ] . An op t imiza t ion of t h e device

con ta in ing t h e d e b r i s bed i s c a r r i e d o u t ; t h i s r e q u i r e s namely a s p a t i a l

f l a t t e n i n g of t h e f i s s i o n and gamma h e a t i n g r a t e . C a l c u l a t i o n s a r e t h e r e f o r e

performed f o r d i f f e r e n t f u e l enr ichments and c o n f i g u r a t i o n s of t h e s t r u c t u r a l

ma te r i a l s .

TIEREAL REACTORS

P r e s s u r e v e s s e l s t u d i e s ....................... The e x p e r i n e n t a l and t h e o r e t i c a l n e u t r o n i c a n a l y s i s o f an a d d i t i o n a l c o n f i -

g u r a t i o n i n PCA (Poo l C r i t i c a l Assembly, ORNL) h a s b e e n comple ted i n t h e

frame of t h e SCK/CEN-participation t o t h e lu2C sponsored P r e s s u r e V e s s e l

S u r v e i l l a n c e Dos ime t ry programme. T h i s c o n f i g u r a t i o n i n c l u d e s a l a r g e

" s l a b s u r v e ? l l a n c e c a p s u l e " (SSC); i t i s a mock-up o f t h e m e t a l l u r g i c a l

i r r a d i a t i ' o n f a c i l i t y P S I (Poo l S i d e ~ a c i l i t y ) a t t h e OR3 t e s t r e a c t o r , f o r

which an i n t e r n a t i o n a l low m d h i ~ h power n e u t r o n i c c h a r a c t e r i z a t i o n h a s

a l s o been a c h i e v e d ( s e e be low) .

The same t h e o r e t i c a l a n a l y s i s h a s b e e n a p p l i e d f o r t h e s t u d y of f l u x p e r -

t u r b a t i o n s due t o t h e z r e s e n c e o f comnerc ia l s u r v e i l l a n c e c a p s u l e s l o c a t e d

be tween t h e t h e r n d s h i e l d and t h e 2 r e s s u r e v e s s e l . Two t y p i c a l c a p s ' d e s

(1" x 1") have b e e n e x ~ o s e d ir ?SF and t h e n e a s u r e d v a l u e s were compared

t o t h e c a l c u l a t e d r e s u l t s o b t a i n e d w i t h DOT [ k ] .

'Ine a p p l i c a t i o n of t h e n e t h o d s h a s been e x t e n d e d t o a r e a l p i a n t , t h e 323

a t MOL. b d e t a i l e d two-dimensional model o f t h e r e a c t o r was s e t up i n

R 8 geomet ry and s e v e r a l c y c l e s we:-e a n a i y s e d . The v a l i d i t y o f t h e computed

s p e c t r e 2nd f l u x l e v e l s was checked a g a i n s t measurements per formed d u r i n g

r e a c t o r o p e r a t i o n [j]. S i m i l a r c a l c u l a t i o n s s?onsored by EPRI were per formed

by R3A ( R a d i a t i o n R e s e a r c h A s s o c i a t e s ) .

The e x p e r i m e n t a l v a l i d a t i o n o f gamma-ray f l u x and s p e c t r a p r e d i c t i o n s i s

i n p o r t a n t a l s o i n o r d e r t o b e t t e r u n d e r s t a n d gamma h e a t i n g i n c o r e i n t e r -

n a l s , s u r v e i l l a n c e c a p s u l e s and t h e v e s s e l w a l l i t s e l f ; a p p r o p r i a t e c o r - - r e c t i o n s f o r photon- induced r e a c t i o n s i n n e u t r o n d o s i m e t e r s r e q u i r e a l s o

gamma d o s e v a i u e s . ~ h e r m o l u n i n e s c e n t ' d o s i m e t e r s ( 7 ~ i ~ ) were i r r a d i a t e d i n

PCA i n o r d e r t o v e r i f y c a l c u l a t e d gamma d o s e o v e r f a s t n e u t r o n f l u x r a t i o s

a t s e v e r a l l o c a t i o n s i n t h e s u r v e i l l a n c e c a p s u l e and i n t h e p r e s s u r e v e s s e l

s i m u l a t o r [ 6 ] . The agreement i s s z t i s f a c t o r y b u t nn a d d i t i o n e l e f f o r t i s

f e l t n e c e s s a r y when u s i n g ganna d o s i g e t e r s i n a r e l a t i v e l y h i g h t h e r a a l

n e u t r o n f l u x .

D i f f e r e n t European and U.S. l a b o r a t o r i e s have p a r t i c i p a t e d i n t h e PSF

c h a r a c t e r i z a t i o n programme with t h e o b j e c t i v e t o v a l i d a t e s u r v e i l l a n c e

dosimetry methods : AEE-Barwell, ECN-Petten, PTB-Braunschweig, RR & A - Derby, HEDL-Richland and SCK/CEN [7]. By r eason of t h e important v a r i a t i o n

of t he neut ron spectrum through PSF, t h e a n a l y s i s of t h e r e s u l t s p rov ides

a severe t e s t of ENDF/B V c ros s - sec t ion d a t a (dosimetry f i l e ) . A s t h e

r e s u l t s of a low power run were combined with t hose of a 1 8 day h igh power

run , t h e response of l ong term f l u e n c e monitors such a s ? 3 ~ b ( n , n ' ) [8] can

be compared with r e a c t i o n r a t e s f o r low f l u x d e t e c t o r s such a s I 0 3 R h ( n , n t )

and 1'51n(n,nl) o f t e n used i n c r i t i c a l f a c i l i t i e s o r benchmark neut ron

f i e l d s . Furthermore, t h e l i n k between S i damage (p.i.n. d i o d e ) and

1 0 3 ~ h ( n , n ' ) could be e s t a b l i s h e d [?I, provid ing t h u s i n d i r e c t l y a t e s t of 02

v a l i d i t y of "Nb(n ,n l ) a s damage ( low t h r e s h o l d ) monitor.

SCK/CZX p e r t i c i p a t e d t o t h e PWR S h i e l s i n g 3enchmark e x e r c i s e sponsored by

t h e hTP.C?.P [IG].

A f u r t h e r ghase of t h e Pressure Vessel Dosimetry S u r v e i l l a n c e programme w L l l

be t h e s tudy of PW2 c o n f i g u r a t i o n s i n t h e ENUS c r i t i c e l f a c i l i t y a t Mol,

i n o rde r t o i n v e s t i g a t e na in ly t h e azimuthal v a r i a t i o n of t h e neut ron snd

ganna f l c x o u t s i d e t h e core (PCA was e s s e n r i a l l y a one-diaeosicnal system

aiming a t t h e s tudy of t h e r a d i a l v a r i a t i o n ) . Tie experiments w i l l s t a r t

a t t h e begLxiing of 1983.

Fue l cyc le ---------- The exper ience with gadolinium poisoned f u e l s t a r t e d with t h e l o a d i n g of

BELGONUCLEAIRE f u e l assembl ies i n Dodewaard i n 1973 and i n BRJ i n 1976.

Since then , t h e u t i l i z a t i o n of gadolinium r o d s has been gene ra l i zed i n BR3. m. d i s has r e s u l t e d i n long r e a c t i v i t y l i f e t i m e s : l e n g t h of cyc l e 4 A was

500 SFPD arid l e n g t h of cyc l e 4B was 360 EFPD ( f o r t y p i c a l l a r g e power p l a n t s ,

t h i s corresgonds t o 24- and 18-month c y c l e s ) . The i n i t i a l des ign of t h e

gado l in iun -con t ro l l ed BR3 co re s r equ i r ed cons iderab le adjustment ; t h e l a r g e

q u a n t i t i e s of mixed oxide and gadolinium f u e l s c o n s t i t u t e a s eve re t e s t of

c a l c u l a t i o n methods. The l a s t cyc l e (43) showed good f i t t i n g between des ign

p r e d i c t i o n and experiment [ l l] .

F u e l a s s e m b l i e s and i n d i v i d u a l r o d s unloaded from 3 R j a r e now examined by

gamma s p e c t r o m e t r y under wa te r i n t h e s t o r a g e w e l l o f t h e p l a n t . The SCK/CEN

gamma s c a n n i n g equipment makes use o f Ge-Li and NaI d e t e c t o r s , su r rounded by

a t h i c k l e a d s h i e l d p r o v i d e d w i t h removable c o i l i m a t o r s . Gadol in ium b e a r i n g

a s s e m b l i e s were examined r e c e n t l y d u r i n g an i n t e r m e d i a t e r e a c t o r shut-down,

p r o v i d i n g t h u s power d i s t r i b u t i o n s a f t e r p a r t i a l burn-up o f t h e gado l in ium.

- BELGONUCLEAIRE p a r t i c i p a t e s t o t h e CSNI Working Group on C r i t i c a l i t y Codes

f o r S p e n t LWR F u e l T r a n s p o r t C o n t a i n e r s . S t a n d a r d i z a t i o n and v a l i d a t i o n o f '

computer c o d e s a r e n e c e s s a r y f o r e s t a b l i s h i ~ g i n t e r n a t i o n a l r e g u l a t i o n s .

Noise a n a l y s i s - - - - - - - - - - - - - - a LASOR3LZC r e p r e s e n t e d Se ig ium a t t h e SMOBN-111 mee t ing i n Tokyo. I n c o l l a -

b o r a t i o n wi th F r a n c e , e x p e r i m e n t a l i z v e s t i g a t i o n s end a n a l y s i s o f v a r i o u s

n e c h a n i c a l and t h e r m o h y d r z u l i c phenonena a t t h e TIFiANGZ I r e a c t o r were

r e p o r t e d [12]. Hore a r t i c d a r i y , abnormal v i b r a t i 0 r . s induced by c r o s s f l o w

j e t t i n g i n t h e p e r i p h e r a l f u e l r o d s were e c ? h a s i z e d .

YLkT3i;LAi TSSTING REACTCR 332

The r e d u c t i o n o f t h e uranium enr i chment i n t h e 3R2 r e a c t o r i s b e i n g con-

s i d e r e d . I n o r d e r t o m a i n t a i n t h e i r r a d i s t i o n c a p a b i l i t i e s w i t h o u t chang ing

t h e geometry o f t h e f u e l e l e m e n t s , t h e uranium d e n s i t y i n t h e meat s h o u l d

3 ';.

i n c r e a s e d from 1.3 g/cm3 ( p r e s e n t s i t u a t i o n up t o 7.0 s/cm ; t h i s would a l l o w

t o r e d u c e t h e en r i chment from 9 0 % t o 20 % 2 3 5 ~ . Uranium s i l i c i d e f u e l s have '

t h e r e f o r e t o b e deve loped wi th s u c c e s s [ I j] . A d e m o n s t r a t i o n i r r a d i a t i o n

programne w i l l b e s e t up.

POWZR PLANTS

Two new n u c l e a r power p l a n t s a r e b e i n g s t a r t e d i n t h e p e r i o d Ju ly -Oc tober

1982 : DOEL I11 and TIFANGE 11, two ?W2's e a c h of 900 W e . About one t h i r d

o f t h e e l e c t r i c i t y p r o d u c t i o n i n 3e lg ium w i l l t h e n be o f n u c l e a r o r i g i n .

DOEL 1'4 and TIHANGE 111, u n d e r c o n s t r u c t i o n , w i l l b e o p e r a t e d from 1985

onwards.

References

[ i j YXSSANDRE - A two-dimensional program f o r r e a c t o r t r a n s i e n t s a n a l y s i s . , us ing t h e gene ra l i zed q u a s i s t a t i c method : s t a t u s and benchmark r e s u l t s " ,

B. Arien e t a i . , I n t e r n a t i o n a l Topica l Meeting on LMFBR S a f e t y and r e l a t e d

des ign and o p e r a t i o n a l a s p e c t s , Lyon, J u l y 19-23, 1982.

[2] T h e European ?Am In-Pi le programme o b j e c t i v e s an6 gene ra l lay-out" ,

H. Backs e t a l . , I n t e r n a t i o n a l Topica l Meeting on LMFBR S a f e t y and r e l a t e d

des ign and o p e r a t i o n a l a s p e c t s , Lyon, J u l y 19-23, 1982.

[3]' "European PAW experiments i n t h e BR2 r e a c t o r " , C. J o l y e t al.,

I n t e r n a t i o n a l Topical Meeting on LmBR S a f e t y and r e l a t e d des ign and

o p e r a t i o n a l a s p e c t s , Lyoc, J u l y 19-23, 1982.

[4] 1fSa-veil lance capsule p e r t u r b a t i o n s t u d i e s i n t he PSF 4/12 conf igu ra t ion" ,

E. Tourwk, G. Minsa-t, Fourth ASTX-ZUBATOM Symposium on Reactor Dosimetry,

NYS, Washington D C , Earth 22-26, 1982.

[5] "Calcu la t ion of t h e f a s t neu t ron f l u x and damage i n t h e p r e s s u r e v e s s e l

of t h e 323 r e a c t o r t 1 , G. Minsart e t a l . , Four th ASTM-EbXATOM Sylr.osi&n on

Reactor Dosimetry, NBS, Washington D C , March 22-26, 1982.

[6] llGanma dosimetry and c a l c u l a t i o n s " , N. Maene e t al., Tourth ASTM-EURATOM

Synpos im on Reactor Dosimetry, NBS, Washington D C , March 22-26, 1982.

[7] l l l n t e r l a b o r a t o r y comparison of f l uence neut ron dos imeters i n t h e frame

of t h e PSF s t a r t - u p measurement programme", ii. Tourw6 e t al., Fourth

ASTM-EUBATOM Symposium on Reactor Dosimetry, NBS, Washington DC,

March 22-26, 1982.

[8] "Niobium dosimetry in te rcompar i son i n EBR I1 and BR2", K. Tourwk e t e l . ,

Fourth ASTM-ELRATOM Symposium on Xeactor Dosimetry, NBS, Washington DC,

March 22-26, 1982.

[9] "S i l i con p - i - n . diode neut ron damage monitors", S. De Leeuw, R. Menil,

Four th ASTM-EUZATOM Symposium on Reactor Dosimetry, NBS, Washington D C ,

March 22-26, 1982.

[ l O j "Cont r ibu t ion t o t h e r e a c t o r s h i e l d i n g benchnaric e x e r c i s e n o 2 (PWR)",

Ch. De Raedt , S p e c i a l i s t s Meeting, P a r i s , J u l y 1-2, 1982.

, , [;I] ~fImprovements r e s u l t i n g from plutonium and gadolinium u t i l i z a t i o n and

r e l e t e d exper ience" , E. B a i r i o t e t a i . , I n t e r n a t i o n a l ENS/ANS Conference

(ENC-31, 3 r u s s e l s , A p r i l 25-30, 1982.

[12] "PWR Core Monitor ing by In-Core Noise Ana lys i sw , P. Bernard e t a l . ,

Third S p e c i a l i s t s Meeting on Reac tor Noise (SMORN I I I ) , Tokyo,

October 26-30, 1981.

[ l j] "The s t a t u s of f u e l element technology f o r p l a t e - type d i s p e r s i o n f u e l s

with h igh uranium dens i ty " , M. Hrovet e t e l . , I n t e r n a t i o n a l ENS/ANS

Conference (ENC-3), 3 r u s s e l s , A p r i i 26-30, 1982.

CANADA

REACTOR PHYSICS ACTIVITIES I N CANADA


P.H. Garvey

Summary

Support of the design and opera t ion of the cu r ren t CANDU PHW r e a c t o r s

continued through t h e development, v a l i d a t i o n and a p p l i c a t i o n of var ious

computer codes, both by Ontario Hydro (OH) and the Engineering Company of

AECL (AEC-EC). I n i t i a l design s t u d i e s f o r a 950 MWe CANDU PHWR were

completed by EC-EC. An i n i t i a l study is being undertaken by AECL on the

des ign of a 750 MWth organic cooled CANDU t o produce steam f o r the in-s i tu

recovery of o i l from t a r sands. Development of the low power hea t ing

r e a c t o r SLOWPOKE-3 continued.

The Reactor Physics program w i t h i n the Research Company of AECL

(AEC-RC) i s mainly a s soc ia t ed with the development of Advanced Fuel Cycles

f o r the CANDU PHWR. The major a c t i v i t i e s wi th in t h i s a rea were development

and v a l i d a t i o n of l a t t i c e c e l l codes, assessment of the c h a r a c t e r i s t i c s of

a thorium f u e l l e d CANDU PHWR, and system s t u d i e s showing the impact of such

f u e l cyc les on uranium requirements. A s u b s t a n t i a l program is a l s o being

implemented i n t h e WR-1 r e sea rch r e a c t o r to determine t h e c h a r a c t e r i s t i c s

of both Tho2 and (Pu,Th)02 f u e l during i r r a d i a t i o n . This da ta w i l l be used

t o v a l i d a t e both codes and da ta .

Fu r the r code development and a p p l i c a t i o n continued wi th in E C - R C i n

support of the research r e a c t o r s NRX, NRU and WR-1. These a c t i v i t i e s have

been complemented by an experimental program i n the ZED-2 zero energy

r e sea rch r e a c t o r a t CRNL.

Studies of the neut ronics c h a r a c t e r i s t i c s of conceptual t a r g e t s f o r

t h e Accelera t ion Breeder continued and f u r t h e r experiments were undertaken

t o determine t h e neutron y i e l d from t a r g e t s i r r a d i a t e d with 100 MeV protons.

A new f u e l managemer.: ?rogram (SIUODEX), based upon 2 m d a l expans ion

memod f o r :he f l u x c i l c u l a i l o n , i s be iag developed by OH. X s i rnu la t io r . of

100 f u l l power days of t h e D a r l i n g t o n r e a c r o r , c-rrer.:ly uader c o n s t r u c t i o n ,

has shorn(!) good accuracy 2nd low c o c p u t i n g cos:s cased =?on comparison

wi rh e x i s t i n g methods.

The f u e l management d e s i g n code (OFlhFS?) h a s been compared by OE w%th

o p e r a t i n g d a t a f rom t h e Bruce NGS A and P i c k e r i n g NGS A s t a t i o n s . T h i s

compar ison has l e d t o improvements i n methodology and has v a l i d a t e d t h e

program. A r e p o r t ( 2 ) documents t h i s work and i n c l u d e s s t a r i o n o p e r a t i n g

d a t a and computer models f o r u s e i n v a l i d a t i o n and o t h e r f u e l management

programs. Th i s r e p o r t is being made a v a i l a b l e t o t h e I& i a t h e c o n t e n t

of a c o o r d i n a t e d r e s e a r c h program on 5 - c o r e f u e l mmagement.

Developmen: by OH of t h e s r a t i c and k i n e t i c s codes (SHOKIN/SHOWP),

based apon t h e n o d a l approach , con::nued. These ?rograms a r e now r o u t i n e l y

used f o r c o n t r o l and shu:dowc s y s z e z ? e r f o m a n c = a n s l y s i s and a l s o co s t u d y

:he l o a d f o l l o w i ~ g c a ? a b i l i t y of CAY32 r e a c f o r s .

Code development of a s i ~ l a r !chd i s k i 3 g cnderraker . by .ZC-EC, is

which s e t h o c s a r e b e i a g i ~ p l e n e n t e d of s i g n i f i c a c t l y lower c36 t buf

comparable accuracy fo e x i s t i n g ne rhods . A t h r e e d i s e n s i o n a l ? d o e t i c s code

(STUIL-4) , based upon :he n o d d model, has been developed t o e v a l u a t e t h e

c o n t r o l r e s p o r s e of t i e C m I ! ?Zm% - h e n s u b j e c r ro v a r i o u s p e r r u r b a r i o n s ,

such a s t h o s e due :o c h a n n e l r e f u e l l i n g . A t h r e e d imens iona l k i n e t i c s code

(DEUTZ.SONOk%), which s o l v e s t h e n e u t r o n k i n e t i c s equac ions by f l u x

s y n t h e s i s , has been developed. I t s computa t ion c o s t is a f a c t o r of 10

lower :Pan CE?&ERUS, a q u a s i - s t a t i c k i n e t i c s code.

A bundle c o u n t e r f o r s a f e g u a r d s m o n i t o r i n g of d i s c h a r g e d f u e l from a

C X W U PIIWR h a s been d e s i g e d and commissioned. A p o r z a b l e 91•‹ s o n i t o r ,

used t o measure t h e 310 c o n t e n t i n t h e m d e r a t o r of a C M D U r e a c t o r , has

been commissioned.

The standard decay heat da t a recommended i n ANS 5.1 f o r CANDU f u e l has

been compared with ORIGEN generated d a t a , the ORIGEN code having previous ly

been compared wi th experimental da t a . It has been concluded by OH t h a t

t h e r e is no longer a need t o apply a contingency f a c t o r of 204 t o the

ANS 5.1 va lues .

A benchmark experiment of n a t u r a l uranium metal rods a t two hexagonal

p i t ches (14 and 24 cm) i n D20 has been completed i n ZED-2. Measurements

were made of t h e usua l r e a c t i o n r a t e s and f l u x d i s t r i b u t i o n s a g a i n s t which

l a t t i c e c e l l codes can be va l ida t ed .

Advanced Fuel Cycle S tud ie s

Development and assessment of Advanced Fuel Cycles f o r the CANDU

r e a c t o r continued wi th in AECL-RC.

A s u b s t a n t i a l program has been implemented f o r the WR-1 r e sea rch

r e a c t o r i n which the seven c e n t r a l l a t t i c e s i t e s w i l l be f u e l l e d with Tho2

f u e l bundles snd subsequently with (2.25 w t % Pu,Th)02 f u e l bundles. The

purpose of t h i s program i s t o o b t a i n da ta on the changing c h a r a c t e r i s t i c s ,

such as power and r e a c t i v i t y , of t h i s f u e l during i r r a d i a t i o n aga ins t which

neut ronics codes and da ta can be assessed . On d ischarge the i s o t o p i c

content of the f u e l w i l l be measured. P r i o r t o i n s e r t i o n i n kR-1 t h e

c h a r a c t e r i s t i c s of the (Pu,Th)02 f u e l w i l l be measured i n ZED-2.

The N J O Y system has been implemented on t h e CRNL CDC computers and has

been used to prepare EM)F/B-V mult igroup da ta f o r t h e l a t t i c e c e l l code

RAMAB-OZMA. L a t t i c e parameters have been ca l cu la t ed f o r a range of thermal

r e a c t o r benchmark l a t t i c e s and the comparison with the measured parameters

r epor t ed (3 ) . Ca lcu la t ions f o r t h e thorium l a t t i c e s were cons i s t en t with

c a l c u l a t i o n s performed elsewhere i n i n d i c a t i n g an underest imation of t h e

thorium resonance capture r a t e by some 6 % . This discrepancy is being

reso lved a t Bh'L by a change i n t h e ENDFIB-V da ta tape , the new 'data being

c o n s i s t e n t with d i f f e r e n t i a l da ta .

Multigroup da ta f o r Co-59, 1-135, V and T i has been added to the

WIMSD-CRNL l i b r a r y , again us ing NJOY and ENDFIB-V data .

Various i;lpravements t o :he kTEiSD-CiLc code , a a i 2 . y i n c k t a h a n d l i n g

anc s t o r a g e , have r e c u c e i i z s c o s t . S r r b s t a n t i a l cos: h . ? r o v e ~ e n t s have . . . a l s o o c c u r r e d th rough t h e use of a 2 0 - g r o q il3rrr;J and s i x c z i 2 : r anspor t

g roups w h i l e r e t a i n i n g acce?t.ahle a c c u r a c y .

F u r t h e r i n c e g r a l c r o s s - s e c t i o n n e a s u r e n e n t s Tere =de i;.. a 3 a u i d

n i t r o g e n cooled p a r a f f i n b lock i n ZZD-2. H e z s u r m e n t 22s o i t h e

f i s s i o n c ross - secc ions of 0-235, U-233 and Pu-230 and t h e c a p t u r e c r o s s -

s e c t i o n s of Th-232, U-238, Cu-63, In-115, Au-!97, and Lu-175 r e l a t i v e t o

t h e c a p t u r e c r o s s - s e c t i o n of En-55. No s i , m i f i c a n t d i s c r e p a n c y from

ENDF/B-V d a r a has been i d e n t i f i e d .

F u r t h e r sysrem s t u d i e s t o e v a l u t t e t h e impact of advanced f u e l c y c l e s

on u r t ~ A u m r e q u i r e n e n c s i n an expanGing n u c l e z r sys tem v e r e m d e r t a k e n ( 5 )

h a n a l y s i s w a s comple ted(5) of once-through r h o r l - a c y c l e s 3 CANDU

r e a c t o r s .

A s u i t a b l e c snb iaa r - ion of codes has ' k e n i c e s z i f i e d v i c h &i..ic!? t o

de te rmine t h e charac:eris:ics 02 t h o r i u m - f x e l l e c C A N X r e a c t o r s . Calcu-

Lacions a r e c u r r e n t l y i- band t o deierzine ax%: ?owe: c i s t r i b u c i o n s :or . - .

v a r i o u s f u e l m n a g e n e n t s : r z t eg ies anti i L i c i a l f u e l z l s s i l e c 0 n p c s i : i n s .

A n u n e r i c e l - s thod sf eval ,~a: ing t h e g e n e r r l i r e d ex?onecc ia l i n z e g r a l s

3 j ( x ) h a s k e n deve loped , ia t h e c d u r s e of = e v e l o p i n g a new method ts s o l v e n rhe n e u t r o n t r a n s p o r r e q u a t i o n s .

Research R e a c t o r s

F u n h e r development of i n t e r a c t i v e , fine m s h n e u t r o n d i f f u s i o n codes

t o i d e n t i f y s u i t a b l e c a l c u l a t i o n , schenes f o r hiU and XRX c o n t i n u e d . These

n e t h o d s a r e be ing v a l i d a t e d f o r s p e c i f i c a s s e n b l i e s by exper iments i - ~

~ ~ ~ - 2 ( 6 , 7 ) .

Advanced S y s t e m

3easuremen:s were m d e of t h e t h e m i nerrtron f l u x O i s t r i S u t F o n Ln an

320 n o d e r a c o r s u r r o u n d i n g a l i t h i u n Earget h e r i r ; ad ia red w i ~ h 100 UeV

protc Ins f r om the McGill Univers i ty cyclotron. These wasurements and

a s soc ia t ed c a l c u l a t i o n s were repor ted(8) a t the ICANS-VI conference a t ANL

i n 1982 Ju ly .

Fu r the r c a l c u l a t i o n s of the f i s s i l e product ion and heat genera t ion i n

conceptual Acce le ra to r Breeder t a r g e t s were completed and r epor t ed (9 ) .

New Appl ica t ions

Determinat ion of the r e a c t o r physics c h a r a c t e r i s t i c s of the 2 MW

SLOWPOKE-3 hea t ing r e a c t o r continued. Parameters such as core l i f e t i m e and

power d i s t r i b u t i o n , r e f l e c t o r worth, and var ious r e a c t i v i t y feedback

c o e f f i c i e n t s a r e being evalua ted .

0

References

1 . " S i m u l a t i o n of D a r l i n g t o n % e l l i n g vi:S SIVODZX, a Fue l Uaaagement

Program Sased on Hodal Expansion" by 4 . i . cigh: and P. Wiebe, Canadian

Nuclear S o s i e t y 2nd Annual Confe rence 1981, ISSN G22i-0129.

7 - . V a l i d a r i o n of OWS? Agairs: A c t u a l 0perz:ing Exper ience" by

ILL. Wign:, O n t a r i o 3ydro Design and Development D i v i s i o n Repor: 81069

(1982) .

3. " T e s t i n g of ENDFIB-V Data f o r Thermal R e a c r o r s " by D.S, C r a i g , Atomic

Energy of Canada L i m i t e d , Repor t AECL-769C ( 1 9 8 2 ) .

4 . - "CANDU - The V e r s a t i l e Opt ion" by J . Veeder and J.V. Donnel ly , h ' S / M S

Conference on New D i r e c r i o n s i n Nuclear Energy, S r u s s e l s , A p r i l , 1982.

5 . "Once-Through Thorium Cyc les i n Ck\?U Reacrors" by U.S. Uilgraffi , Atocic

3e rg -y of Canada LiA:ed, Xeport PZCL-7516 ( :982).

6 . "ZED-2 Zx?erhen:s L3 S u ~ p o r t of ?a-99 3roduc:ion i3 NRU* by R.T. J o n e s ,

Atomic Energy of CanaCa L i n i t e d , Re?or: ECL-i335 ( 1981 ) .

7 . "Co am5 Cd >-SsorSer Xod Zjrperiments i r ZZ9-2" by G.U. .Lrbique, Atomic

Znergy of Canecia Lini:ed, Repor: .GCL-i5i4 ( ? 9 8 ? ) .

8 . "Xeasured and C a l c u l a t e d Neutron Y i e l d s f o r 100 HeV E o t o n s on Th ick

T a r g e t s 05 F'b and T i " by R.T. Jones e t a l . , ? roc . I W S - V I , ANI., J u l y ,

1982.

9. "A Review of P r o s p e c r s f o r an A c c e l e r a t o r Breeder" by J.S. F r a s e r e t

a l . , Atomic Energy of Canada L i m i t e d , Repor: AECL-7260 (1981) .

R i s 0 N a t i o n a l L a b o r a t o r y

DENMARK

S e p t e m b e r 1 9 8 2

HN/ik-15

R e c e n t R e a c t o r P h y s i c s A c t i v i t i e s i n Denmark

by

Hans N e l t r u p

'. The e f f e c t o f u s i n g lower e n r i c h m e n t i n r e s e a r c h reactors

T h e s t u d y o f t h e c o n s e q u e n c e s o f u s i n g lower e n r i c h e d f u e l

( 2 0 % ) i n t h e h e a v y water r e s e a r c h r e a c t o r DR 3 h a s b e e n c o n -

t i n u e d a n d b r o u g h t t o a t e m p o r a r y c o n c l u s i o n : The m e t h o d s u s e d

h a v e b e e n c o m p a r e d t o t h o s e o f o t h e r l a b o r a t o r i e s t h r o u g h a n

i n t e r n a t i o n a l b e n c h m a r k s t u d y u n d e r t h e a u s p i c e s o f I A E A , a n d

w i t h some m o d i f i c a t i o n o r i g i n a t i n g f r o m t h i s s t u d y a p p l i e d t o

o u r p r o g r a m m e s w e now f e e l c o n f i d e n t a s t o c a l c u l a t i n g t h e

c h a r a c t e r i s t i c s o f f u e l s o f d i f f e r e n t e n r i c h m e n t s i n DR 3 .

T h e main m o d i f i c a t i o n w e i n t r o d u c e d was t h e r e p l a c e m e n t o f t h e

r o u t i n e f o r r e s o n a n c e c r o s s s e c t i o n c a l c u l a t i o n s w i t h a n e n t i r e - * l y new o n e b a s e d o n t h e s o - c a l l e d s u b - g r o u p method .

We h a v e d e v e l o p e d t h e me thod a l i t t l e f u r t h e r f r o m o u r f i r s t

v e r s i o n , m a k i n g i t more " p h y s i c a l l y s o u n d " . I n s h o r t t h e m e t h o d

a s s u m e s t h a t t h e s e l f - s h i e l d e d r e s o n a n c e c r o s s s e c t i o n o f a n

a b s o r b e r c a n be w r i t t e n a s a sum o f a r e l a t i v e l y s m a l l number

o f terms ( - 5-8 terms)

- 1 'i - w . ' e f f - 1 i

I n o u r . f i r s t v e r s i o n o f t h e me thod t h e w e i g h t s w i w o u l d come

o u t w i t h b o t h p o s i t i v e a n d n e g a t i v e v a l u e s . A s w i i n e f f e c t

m u s t b e i n t e r p r e t e d a s l e t h a r g y w i d t h s , n e g a t i v e v a l u e s g i v e

n o p h y s i c a l m e a n i n g . By means o f a n o n - n e g a t i v e l e a s t s q u a r e s

fitting procedure using a quadratic ~rogramming technique we

have avoided the negative wi's. It should be noted, though,

that the results of the new method only differ slightly from

the old ones with mixed positive and negative wits.

2. Resonance cross sections for 238"

2 3 8 ~ resonance cross sections used at Risa have until recently

been generated from resonance parameters published in 1965 (1).

A.certain ad hoc reduction recommended in (2) and introduced in

WIMS was adopted with quite satisfactory results, but it was

felt that such a correction should only be provisional and be

discarded, when better fundamental data became available.

The publication of new and presumably better resonance par-

ameters for 2 3 8 ~ in (3) initiated the establishment of a new

resonance library, RESLIB/DSOP. The subscript refers to the

names of the four authors.

Several benchmarks were recalculated with the new library show-

ing that the changes caused by the new resonance parameters by

and iarge corresponded to the ones caused by the previous ad

hoc correction. So far a quite satisfactory result. However it

seems that still better results with regard to b.o.1. reactivity

and plutonium production are obtained, when the old ad hoc

reduction is made on the new cross sections.

3. Iterative methods and nodal theory

Alternative iterative methods for solution of the equations used

in the MIT nodal programme Quandry ( 4 ) are being investigated.

So far only the simplified case of one neutron energy group and

flat transverse leakage has been studied. It appears that a

significant decrease in running time (a factor of 3 for 3-di-

mensional, 5 for 2-dimensional problems) can be obtained by

suitable preconditioning and application of one of the known

methods for iterative solution of a non-symmetric system of

l i n e a r e q u a t i o n s . The b e s t c h o i c e seems t o be a s i m p l i f i e d f o r m

o f t h e g e n e r a l i z e d c o n j u g a t e r e s i d u a l m e t h o d , b u t a l s o t h e un-

s y m m e t r i c L a n c z o s - a l g o r i t h m a n d A r n o l d i ' s me thod c a n b e u s e d .

The new t e c h n i q u e s a r e b e i n g i n c o r p o r a t e d i n t h e Q u a n d r y pro-

gramme i n t h e h o p e t h a t t h e y w i l l b e u s e f u l a l s o f o r more re-

a l i s t i c p r o b l e m s .

4 . ANTI

ANTI is a c o m p u t e r p r o g r a m f o r t h r e e - d i m e n s i o n a l c o r e t r a n s i e n t

c a l c u l a t i o n s . I t is a c o m b i n a t i o n o f t h e n o d a l t h e o r y n e u t r o n

p h y s i c s p a r t o f t h e BWR p r o g r a m ANDYCAP a n d t h e s u b c h a n n e l

t h e r m o - h y d r a u l i c p r o g r a m TINA. T e s t c a l c u l a t i o n s w i t h t h e s t e a d y

s t a t e p a r t o f ANTI are s t i l l g o i n g o n , i n w h i c h c o m p a r i s o n s are

made w i t h d a t a f r o m t h e u p s t a r t o f t h e R i n g h a l s 3 , W e s t i n g h o u s e

PWR .

A s m e n t i o n e d e a r l i e r t h e n o d a l me thod i n c o r p o r a t e d i n ANDYCAP

i n t r o d u c e s a c e r t a i n d e g r e e o f a r b i t r a r i n e s s t h r o u g h t h e so

c a l l e d g - f a c t o r s , w h i c h c a n n o t be d e r i v e d f r o m f u n d a m e n t a l

d a t a , b u t h a v e t o be f i t t e d e m p i r i c a l l y . To i m p r o v e t h i s s i t u -

a t i o n r e p l a c e m e n t o f t h e n o d a l p a r t o f ANDYCAP by a N o d a l

E x p a n s i o n Method ( N E M ) p rogramme, ( 5 ) i s a n t i c i p a t e d . An import-

a n t p r o p e r t y o f t h e NEM is t h a t t h e b a s e q u a d r a t i c v e r s i o n c o n -

v e r g e s t o w a r d s t h e e x a c t s o l u t i o n o f t h e d i f f u s i o n e q u a t i o n

when t h e m e s h s i z e is r e d u c e d ( 4 ) . A p r a c t i c a l a d v a n t a g e w i t h

t h e NEM is t h a t t h e p o l y n o m i a l e x p a n s i o n c o e f f i c i e n t s n e e d n o t

b e s t o r e d d u r i n g i t e r a t i o n . O n l y c o a r s e mesh a v e r a g e f l u x e s

a n d p a r t i a l c u r r e n t s m u s t b e k e p t i n s t o r a g e .

The p r e s e n t NEM-version w o r k s w i t h Znd, 3 r d , a n d 4 t h o r d e r f l u x

e x p a n s i o n s a n d O t h , l t h , a n d 2nd o r d e r t r a n s v e r s e f l u x l e a k a g e . I t

h a s b e e n t e s t e d o n v a r i o u s b e n c h m a r k s ( 4 ) , A p p e n d i x 4 , a n d i n

p a r t i c u l a r o n t h e 2D IAEA-benchmark. I n F i g . 1 is i l l u s t r a t e d

t h e i n f l u e n c e o f t h e o r d e r o f f l u x e x p a n s i o n a n d t r a n s v e r s e

l e a k a g e o n t h e r a t e o f c o n v e r g e n c e f o r t h i s b e n c h m a r k .

5 . D e t e r m i n a t i o n o f l o c a l p i n Dowers from a l o b a l 3 D coarse-mesh

s o l u t i o n s

D i f f e r e n t ways o f r e g a i n i n g t h e i n f o r m a t i o n on l o c a l p r o p e r t i e s

o f s i n g l e h e t e r o g e n e o u s s u b a s s e m b l i e s a f t e r t h e 3 D coarse-mesh

s o l u t i o n has been found have been i n v e s t i g a t e d (6). The Super-

p o s i t i o n Method proved t o be s u p e r i o r t o t h e o t h e r p in power

models examined provided b o t h e f f i c i e n c y and accuracy are con-

s i d e r e d (compare T a b l e 1 ) .

The S u p e r p o s i t i o n Method i s a t h e o r e t i c a l l y e x a c t method o f c a l -

c u l a t i n g l o c a l p i n power d i s t r i b u t i o n s . The s u p e r p o s i t i o n pr in -

c i p l e c o n s i s t s i n s o l v i n g t h e d i f f u s i o n t h e o r y e q u a t i o n by

d i v i d i n g t h e problem i n t o a number o f subproblems a l l hav ing

d i f f e r e n t boundary v a l u e s . F i r s t , t h e s e subproblems a r e s o l v e d ;

n e x t , t h e f i n a l s o l u t i o n i s o b t a i n e d by combining a l l t h e s o l -

u t i o n s t o t h e subprob lems . The number o f subproblems r e q u i r e d

depends on how d e t a i l e d t h e shapes o f t h e boundary parameters

a r e t o be approximated and t h e number o f e n e r g y groups i n wh ich

t h e boundary parameters a r e r e p r e s e n t e d .

The S u p e r p o s i t i o n Method has a c e r t a i n c o n f o r m i t y w i t h r e s p o n s e

m a t r i x methods . However, i t i s more f l e x i b l e , because it need

n o t be t h e parameter d e r i v e d f rom t h e g l o b a l s o l u t i o n , which i s

used a s boundary parameter i n t h e subproblem d e f i n i t i o n . N e i t h e r

a r e t h e r e r e q u i r e m e n t s about a u n i q u e r e l a t i o n be tween t h e

number o f boundary parameters d e r i v e d f rom t h e g l o b a l s o l u t i o n

and t h e number o f subprob lems . I f t h e number o f g l o b a l boundary

parameters e x c e e d s t h e number o f subproblems t h e f i n a l s o l u t i o n

i s d e f i n e d t o be t h e one i n which t h e c o m b i n a t i o n o f boundary

v a l u e s i n t h e subproblems makes t h e b e s t match t o t h e boundary

parameters f rom t h e o v e r a l l s o l u t i o n .

I n t h e p a r t i c u l a r c a s e where t h e subproblems are d e f i n e d s o

t h a t t h e parameter used a s a boundary c o n d i t i o n i s u n i t y on one

p a r t o f t h e boundary and z e r o on t h e remain ing p a r t , and f u r t h e r -

more i f t h e parameter d e r i v e d f rom t h e converged g l o b a l s o l -

u t i o n i s t o be used t o d e f i n e t h e boundary c o n d i t i o n s f o r t h e

subprob lems , t h e n t h e S u p e r p o s i t i o n Method and r e s p o n s e ~ n a t r i x method w i l l be i d e n t i c a l .

I f t h e base s o l u t i o n used i n the s u p e r p o s i t i o n scheme a r e de-

f i n e d u s i n g . J /0-parameters a s boundary c o n d i t i o n s , one can

p r e d i c t p in powers w j . t h a maximum e r r o r of - 5 % using only s i x

base s o l u t i o n s . Due t o symmetry i n p i n enr ichment , on ly t h r e e

boundary va lue c a l c u l a t i o n s need be so lved i n o r d e r t o o b t a i n

t he s i x base s o l u t i o n s . The computing t ime r e q u i r e d t o g e n e r a t e

t h e s i x base s o l u t i o n s is measured t o be about a f a c t o r of two

g r e a t e r t han t h e "normal" assembly c a l c u l a t i o n .

Moreover, i t has been demonstra ted t h a t an a c c u r a t e d e t e r m i n a t i o n

of l o c a l p in powers r e q u i r e s knowledge of t h e hetorogeneous o r

" equ iva l en t " boundary paramete r v a l u e s from t h e converged g l o b a l

s o l u t i o n . Fur thermore , i t is no t s u f f i c i e n t t o use t h e average

v a l u e s of t h e boundary paramete r v a l u e s i n t h e pin-power models:

A f i r s t - o r a second-order polynomial approximat ion of t he

shape of t he boundary paramete rs is r e q u i r e d .

i t has been shown t h a t t h e accuracy of a p r a c t i c a l use of t he

l o c a l pin-power models is poor i f t he c o a r s e mesh s o l u t i o n is

based on f lux-weighted homogenized paramete rs (compare Table

1 ) . Hence, o t h e r homogenization schemes should be i n t roduced i f

t he p i n powers a r e t o be a c c u r a t e l y p r e d i c t e d .

One of t he major f i n d i n g s is t h e r e f o r e t he c l o s e connec t ion

between t h e homogenization scheme, t h e nodal coarse-mesh method,

and t h e l o c a l pin-power model. H i s t o r i c a l l y , t h e s e t h r e e s u b j e c t s

were i n v e s t i g a t e d i n sequence, and i t is on ly now a f t e r p r o g r e s s

has been made i n a l l t h r e e a r e a s t h a t t h e c l o s e connec t ion can

be recognized . Consequent ly , an i t e r a t i v e p rocedure between

homogenizat ion, coarse-mesh c a l c u l a t i o n , and pin-power de te rmi-

n a t i o n is r e q u i r e d i n o r d e r t o o b t a i n f a i r l y a c c u r a t e s o l u t i o n s .

However, based on t h e r e s u l t s from t h e S u p e r p o s i t i o n Method, i t

proved t o be p o s s i b l e t o avo id t h e r a t h e r time-consuming i t e r -

a t i v e p rocedure by use of t he s u p e r p o s i t i o n scheme i n t h e

g l o b a l 3D coarse-mesh c a l c u l a t i o n . The idea is t h a t i f t h e

G e n e r a l i z e d Equivalence Theory ( 7 ) is a p p l i e d and the d i s c o n t i -

n u i t y f a c t o r s a r e c a l c u l a t e d f o r each boundary-value problem i n

t he base s o l u t i o n g e n e r a t i o n , then i t is p o s s i b l e t o deve lop

the " a c t u a l " discontinuity f a c t o r s us ing t he s u p e r p o s i t i o n

scheme during the coarse-mesh so1u:ion. This idea has not

been examined yet, but seems to be an interesting topic for

furter investigation.

6. Fuel Management

The fuel management program S O F I E is used by Danish utilities

at regular intervals, when the economy of nuclear power is up-

dated. A new fast routine to determine the relative power in

three regions has been implemented. The method involved uses

the analytical solution of the two-group, three-region diffusion

equation. In order to find the first zero of the appropriate

determinant a fast and reliable routine for finding roots in

transcendental equations must be available.

References

(1) J.B. Garg et a?., Phys. Rev. 1378, 547-575 (1965)

(2) F.J. Fayers, P.B. Kemshell, and M.J. Terry, I. Britt. Nucl.

Energy Soc. - 6, 166 (1967)

(3) G. De Saussure, D.K. Olsen, R.B. Perez, and F.C. Difilipo,

Prog. in Nucl. Energy - 3, 87-124 (1979)

(4) Kord S. Smith, An Analytical Nodal Method for Solving the

Two-Group, Multidimensional, Static and Transient Neutron

Diffusion Equation. MIT, March 1979

5 ) H. Finnemann and H. Raum, Nodal Expansion Method for the

Analysis of Space-Time Effect in LWR's. Proceeding of a

Specialist Meeting on Calculations of 3-Dimensional Xating

Distribution in Operating Reactors WEACRP, Paris 26-28,

Nov. 1979, p.p. 257-281.

(6) F. Nissen, Determination of Local Pin Power in the Framework

of Nodal Coarse-Mesh Solutions, Ris0-R-474.

(7) Kord S. Smith, Spatial Homogenization Methods for Light

Water Reactor Analysis, Dissertation, MIT 1980

' T a b l e 1 ~ a x i m u m e r r o r s i n t h e f o r m f a c t o r f o r s u p e r c e l l u s e d i n ( 6 ) * ) u s i n g h e t e r o g e n e o u s - a n d

f l u x - v o l u m e n w e i g h t e d h o m o g e n e o u s b o u n d a r y p a r a m e t e r v a l u e s

L o k a l m o d e l -- T y p e o f b o u n d a r y Maximum e r r o r i n 8 o f a s s e m b l y a v e r a q e p o w e r - -

- -- -- - - -. -- -. - Box - 1 BOX 2 Box 3 Box 4 -- Box 5 Box 6 -- Box 7 -- B O X 8 - B O X - 9 -

N o r m a l i z a t i o n Zero n e t c u r r e n t 2 1 2 7 3 2 28 27 3 5 1 0 7 3 0

F l u x - L u p e H e t e r o g e n e o u s 0

F l u x - L u p e H o m o g e n e o u s 3 6 . 2

S u p e r p o s i t i o n H e t e r o g e n e o u s 5 . 5 4 . 6 4 .7 4 .9 5 . 5 2 .9 5 . 2 2 . 8 2 . 0

S u p e r p o s i t i o n H o m o g e n e o u s 1 6 . 8 1 7 . 8 1 2 . O 1 2 . 8 1 0 . 7 7 . 8 6 . 8 4 . 8 9 . 9

M o d u l a t i o n H e t e r o g e n e o u s 7 . 2 1 2 . 5 6 . 8 4 . 6 5 . 6 5 . 9 1 . 8 1 .1 4 . 7 I

M o d u l a t i o n - tlomoge n e o u s 1 1 . 2 - 1 1 . 0 -- - - 8 . 0 - 2 0 . 1 - 2 6 . 5 1 1 . 6 1 0 . 3 - 9 . 5 .- 4 . 0 lu a,

IAEA - 2 D BENCHMARK

i , j : i - flux exponsion order 2.0 j -transverse leakage order

NODE SIZE (crn)

Fiq. 1

FINLAND

E . q C T O R PHYSICS ACTIVITIZS I S ?I?iLAGD


1 1 the four nuc l ea r power r e a c t o r s i n Finlanci have now

begun the c o m e r c i a l o p e r a t i o n . A t t h e same t ime t:le

c a l z ~ l a t i o n systems f o r bo-;h t y e s of r e a c t o r s ( P V 7 and iWR) +

a r e approaching the mat1:rity i n t he ? iuclear Engineer ing

Labora tory of t h e Technica l Research Cent re of F in l and . The . r e a c t o r s h y s i c s a c t i v i t i e s has somewhat s h i f t e d from the

development of . c a l c u l a t i o n methods and computer programs

towards ana lyses of r e a c t o r o p e r a t i o n . Tne ?X7-simulator

program HZX3U-33 has Seen handed over t o t h e owner of t h e

two ?Ti?-reactors i n F in land and t h e furtFler Seveiopment of

t h e p r o g r a r w i l l be d i r e c t e d a t t h e W3R-1333 r e a c t q r . A

major new p r o j e c t i n t he l a b r a t o r y was t h e d e s i ~ n of a

program system f o r a c c u r a t e c a l c u l a t i o n of t h e f a s t neu t ron

2ose a t t h e p r e s s u r e v e s s e l of FXR-reactars wit:? hexagonal

f u e l assembly geometry.

C e l l c a l c u l a t i o n s

The planned work of v e r i f y i n g the c e l l assembly spectrum and

burnup program CASMO-HEX through comparison wi th o t h e r

programs and with exper iments has s t a r t e d , bu t 6ue t o a

heavy demand f o r manpower f o r o t i ler t a s k s a l l t h a t has been*

c a r r i e d ou t y e t is a comparison with some Hungarian

c a l c u l a t i o n s f o r a c e r t a i n t e s t problem. The d i f f e r e n c i e s

a r e s m a l l , wi th k, d i f E e r i n q by l e s s than 0.01. They

appear t o be caused more by d i f f e r e n t group c o n s t a n t s i n t h e

assembly c a l c u l a t i o n s , e s p e c i a l l y i n t h e resonance range ,

t han by d i f f e r e n c e s i n t h e c a l c u l a t i o n methods. I t is not

known whether t h e group c o n s t a n t d i s c r e p a n c i e s a r e due t o

d i f f e r e n t b a s i c c r o s s s e c t i o n s and resonance parameters o r

t o t h e methods used i n t h e i r p r o c e s s i n g .

(" TECHNICAL RESEARCH CENTRE OF FINLAND ?,T/NUCLEAR E N G I N E E R I N G L A B O R A T O R Y

P.O.B. 169,SF-00181 HELSINKI 18. FINLAND TEL. 90-618931. TELEX 12-2572 VTTlN SF

The c a l c u l a t i o i l scheme is shown i n t he f i c u r e 1. I t s co re is

formed Sy t h e d i s c r e t e o r d i n a t e s program DCT 3.5-E anE t h e

Monre Czr lo p ros ran :%X&i\TS with i t s e v a l u a t i o n procram

EVALO. The use of two q u i t e d i f f e r e n t programs, employing

d i f f e r e n t c a l c u l a t i o n methocs and d i f f e r e n t approximat ions ,

p rov ides a check on our r e s u l t s , a l though t h e use of t h e

same c r o s s s e c t i o n s and t h e same f i s s i o n source d i s t r i b u t i o n

in t roduces a p o s s i b i l i t y of common e r r o r s .

- DOT 3 .5 -E i s used t o c a l c u l a t e f l u x d i s t r i b u t i o n s i n ( r , e ) . and (r, z ) geometry. I t i s then assumed t h a t t h e d e s i r e d

three-dimensional f l ux d i s t r i b u t i o n can be ob ta ined through

C m u l t i p l i c a t i o n of t h e s e two d i s t r i b u t i o n s . To keep t h e

c a l c u l a t i o n t i n e s r ea sonab le , only t h e energy range above

111 keV i s t r e a t e d and t h e 26 BUGLE-80 groups i n t h i s range

a r e co l l apsed i n t o 10 grou2s by ANISN. I n a d d i t i o n t o t h e s e

sou rces of inaccuracy , D3T s u f f e r s from t h e need t o

approximate t h e hexagon21 co re geomet-ry i n t h e ( r , E)

c a l c u l a t i o n .

HEXXVN, on t h e o t h e r hand, t r e a t s t h e ceometry e s s e n t i a l l y

e x a c t l y . Moreover, no croup condensa t ion i s needed, an6 t h e

f l u x is c a l c u l a t e d i n t h r e e dimensions, b u t f o r t h e sake of

o b t a i n i n g decent s t a t i s t i c s t h e az imutha l and a x i a l

d i s t r i b u t i o n s a r e assumed t o Se s e p a r a b l e . Another source of

inaccuracy i s t h e f a c t t h a t , because of t h e need t o l i m i t

t h e c a l c u l a t i o n t i n e , neu t rons a r e not t r a c e d i n t h e c o r e .

I n s t e a d , a s u r f a c e source a t t h e co re s u r f a c e is used, and

t h i s s u r f a c e source i s not e x a c t . I t s spectrum i s taken t o

be t h a t of t h e oiltgoing p a r t i a l c u r r e n t c a l c u l a t e d by AVISV

and its a x i a l d i s t r i b u t i o n i s assumed t o be t h e same a s t h e

a x i a l power d i s t r i b u t i o n i n t h e outermost f u e l e lements . The

d i f f u s i o n program TRIG3N-PV?rT i s used t o c a l c u l a t e t h e

h o r i z o n t a l d i s t r i b u t i o n of t h e t o t a l source ( f i s s i o n + s c a t t e r i n g ) i n t h e core i n about f i v e groups. Employing a

method base6 on i n t e g r a l t r a n s p o r t t heo ry but making some

geomet r i ca l approximat ions , th i s source d i s t r i b u t i o n i s used

The n e u t r o n h i s t o r i e s z r e simillateC: i n t;?e 3'TCLE-63 2 5 g r o c 3

r e p r e s e n t a t i o n w i t : ! F i s c a t t e r i n g c r o s s s e c t i o n s . A s p e c i a l

methoe f o r s e l e c t i n 2 f r o - Pi kru:.cated d e n s i t y f u n c t i o n s h a s

been e l a b o r a t e d . R e c o n v e n t i o n a l e f f i c i e n c y i n c r e a s i r . 5

o p t i 0 r . s o f s u r v i v a l b i e s i n g , i m p o r t a n c e s p l i t t i n g and

X o s s i e n r o u l e t t e , a c i p a t : ? - ~ t r e t c ' p ~ i n q e r e i n c l u 3 e B . 3 e s e 5 on

s i n p l i f i e d c o n s i i e r a t i o n s t h e p c s s l b i l i t y o f an e u t o m a t i c

o p t i m i z a t i c n of 5i.e s p l i t t i n s 2r.C sath-stre:c:?inq paraze:ers

i s i n t r o d u c e s . :ZXZ-?W :=ror',sces a f i l e t h z t c s n t e i n s a

q u a n t i t i e s c h a r a c t e r i s t i c t o v e r i o u s n e u t r o z - e v e n t s i n

... a s s i g n e B r e ~ i o z s , ; r o o r c Z V Z Z ? rod -ces e s r i z a t e s o f ~- p e r t i a l c s r r e r i t s thrgils!: c ive r . s - r f z c e s a r e .cf reec:ion -.

r a t e s i n g iver . r e g i o c s .

- . > . The B i S - d y n a z i c s code TP-, c r , e -cxaezs ionc - 1:: m a j o r

f e a t u r e s , h a s been f u r t h e r e x t e n d e d t o model e f f e c t s h a v i n q

f a s t c o u p l i n g w i t 5 r e a c t i v i t y . l ience t h e new schmode l s f c r

t h e s t e a n l i n e s and t h e main c i r c u l e t i o n _3il;;ii>s a r e a t t a c h e ?

The code i m p r o v e n e n t s i n c l u d e s a l s o t n e o s t i o n t o p e r f o r m

s e p a r a t e h o t - c h a n n e l c a l c u l a t i o n s i n .which t h e a x i a l T w e r

d i s t r i b u t i o r . and t h e h y d r a u l i c bounda-7 c o n r l i t i o z s a r e

o b t a i n e d from the g l o b a l YWX-calcu la t ions v i a a c o n p u t e r

f i l e .

T M 3 h a s been s u c c e s c . ~ l l y used i r . h y d r z u l i c t h r e e - c = r e -

r e s i o r . c a l c u l z t i o n s , Siit t h e 3 0 X A S - b a s e 3 e v a l u e t i o n f o r t h e . - . c o r r e s p o x d i n g n e u t r o n i c s n e e c s e c c l t i o n a l work.

Azimuthal and axial flux distributions a; releva-: radii

t F I N A L R E S U L T S

Fig. 1. Pressure vessel irradiation

calculation scheme

EACPOR PEYSICS ACTIVITIES I N FRANCE

October 1961 - Septerber 1982

24th NEACRP meeting

FRANCE

SeptemDre !SF32

Thi r ty t h r e e nuclear p l a n t s a r e operated i n F W C E , including 24 PWR's and PEENIX, the breeder prototype. The r a t e of nuclear e l ec+z ic ty production has reached 50 % i n some of t h e i a s t months and *e load follow with nuclear s l a n t s has become a necess i ty . No major d i f f f i c u l t i e s appear i n the opera t ion of t l e s e r e a c t o r s and t h e load f a c t o r i s c lose t o 70 % i n agreement with the p red ic t ion values.

The s t a r t -up of t h e f i r s t :300 E?We PWR is forseen f o r the next ye= and w i l l be followed by =he s t a r t .J;, of SUPERPTENIX. The p rogrm of r e a c t o r s under cons t ruct ion includes 25 o the r u n i t s f o r which the order has al ready been del iverec

The reac to r ~ h y s i c s s t u d i e s aim t o t i e improvement of tke design and opera t ion of 3WR's and f a s t breeders and a l s o of t h e f u e l cycle f a c i l i t i e s asso- c i a t e d t o the both types of reac tors .

The major a c t i v i z i e s c f the 'as: Xeactor i h y s i c s irogram during the period Septmber 1981 - SeptemBer 1982 CL? be summarized a s follows :

- Zxtensive cont rc l - roc experimental s t u d i e s , i n p a r t i c ~ i a r i n the framework of e j o i n t CA-ZNEA-3EBENE r o g r a m (RACIiE )

- S-Z'ERPEiENIX s t a r t -up and f i r s t cricicali:y c o n f i q ~ r a t i o n smciies.

2-2 Experimental Studies

2-2-1 PENIX ------

The r e a c t i v i t y b d a n c e meter is r e s e n t l y 3n l i n e , even i f ii; has no s a f e t y functions.

The con t ro l rod experiments a l ready e r f o r m e d z r e being analyzed a some prelim in^^ r e s u l t w i l l be r e s e c t e d ax t h i s meeting /I/.

Dosimetry e x p e r k e n t s , damage r e l a t e d , a r e being perfomed i n a l z z e r a l i n t e r n a l s torage subassembly loca t ion (DINCSAUUE ex?eriaenr);, which:shouid charac- & ~ e r i z e s t e e l damage i n a r e l a t i v e l y s o f t s?ec=rm envlroment .

The sh ie l* design ca lcu la t ion scheme and da ta a r e being va l ida ted i n a d e t a i l e d c a l a l a z i o n of secondary so?i.m ac t iva r ion measured =c PEENIX.

The s t z r t -up c o n f i q r ~ t i o n ane :he c r i t t c a l i : ~ approach szra tegy have heen s t d i e d i.-. or8er f o meet con t ro l and sa fe ry r e T < i r a e n t s .

I t h a s r l s o been, defined a la-rge p a r t of L?E physics experiments a t s t a r t -up : power d i s t r i b u t i o n s i n :ne core i n p e s e n c e of d i f f e r e n t con t ro l rod a t t e - n s , r eac t ion r a t e & s t r i b u t i o n s f a r from core c e n t e r , contzol rod w c r 5 s e t c

Control rod experiments a r e being performed a s planned. Large c e n t r a l con t ro l rod experimental r e s u l t s nave been compared. t o c a l c u l a t i o n s , and a s i m i l a r ana lys i s has been cons i s t en t ly performed f a r some of t i e previous cont ro l rod . experiments of the ?RE-EIACIhJ ?rogram. Some of L?e r e s u l t s w i l l be presented a t t h i s meeting /2/ , and w i l l be presented a'c L\e coming KIAMESEA-LAKZ meeting /3/ together with f-rtner experiment/calculat ion comparisons /4/. The Y heating nea- sureaentsare being analysed and some r e s u l t s w i l l a l s o be reported a t L i i s meeting 151.

The .RACINE progrsrn w i l l be devoted , i n the f i r s t months of next y e a r , t c Experimental s t u d i e s r e l a t e d t o -,ie SLFZiP:%NIX s t a r t -up and severa l s u b c r i t i c a l con5iqdrations w i l l be s tudied .

The mult i?le rod conf igura t ions and the chick f e r t i l e r i n g experiment a r e a l s o planned, a s previously reported.

2 - 2 4 WUWONII sh ie ld ing experiments .............................

The JASON program conf igc ra t iomper fomec ap co now =e Seing malysed , i a par:iculx che ewer imen ta i parmetrical program r e l a t e d t o 54C/ s t e e l confi- "yrat ions.

The nex: phase of JASON 2rogram w i l l be devoted- to s t r ean ing q e r i n e n t s s t r e m i n g i n narrow ducts i n a sodixm environment and s r r e m i n g i n ducts s x r o u n d i : l a r g e sodium tanks.

I n boty cases , szurce e f f e c t s and duct w a l l ma te r i a l and geometry w i i l bt s r Jd ied paametricaliy.

2-2-5 ERMINE experiments -----------------

The low enerqy spectzum conf igura t ion program has been completed and i s beinq analyzed. The Doppler experimental srogram has been delayed a d w i l l be complezec i n +&e f i r s t months of 1983. Anew experimental lrogram is foreseen, s c a r t i n g a t t h e end of 1982, t o s tudy ce l lhe te rogene i ty problems, an2 some pin/ p l a t e comparisons a r e scheduled, using SNEAK p l a t e l e t s .

2-3-1 Xul:idimeasional desiga c a l c u i a t i o n codes ------------------------+----------------

The e f f o r t towards a s u b s t a n t i a l iiqrovement of t h e p resen t mul t idhen- s iona l d i f fus ion Lieory codes zsed f o r design has been continued and w i i l be repor-led a t t h i s meeting / 6 / . The f i n i t e Cifference met\ods f c r homogeneous a d inhomogeneous ca lcu la t ions have Seen improved, tzking acivantage of more gopnis- t i c a t e d proqraming techniques.

Tes ts have Sren - 2erformed on -&e e x p o r t a b i l i t y of new s y s t e i ~ (ECLIPS) which i s being a s s d l . e d , implementing succesful ly t l e s tandard 2C hexagonal modui o r i g i n a l l y programer5 f o r IBM machine, on a CRAY-1 machine.

The new system w i l l . be f u l l y opera t ional a t Lie end of 1983, with both . f i n i t e d i f ference and f i n i t e element c a p z L i i i t i e s and f u l l depier ion and l e r t a r - ba t ion opt: ' ons.

The v a r l a t l o n a l col laps ing procedure f o r few group calcu1at;ons w i l l be reported a t t h i s meetmg / 7 / .

2-3-2 Heterogeneity and Diffusion c o e f f i c i e n t .......................................

P r a c t i c a l app l i ca t ions a r e made of new t h e o r e t i c a l s t u d i e s /8/ on t h e d i f fus ion c o e f f i c i e n t d e f i n i t i o n f o r both power r eac to r core subassembly hetero- g e n e i t i e s and f o r c r i t i c a l experimentce 'Tlconfigurat ions. 30th t h e e f f e c t s on c r i t i c a l mass and sodlum void r e a c t i v i t y e f f e c t a r e being studied. In part icular , t i e p resen t s tmdard apporxinat ions used i n design ca lcu la t ions (based on Zero- order buckling dependence of L\e d i f fus ion c o e f f i c e n t ) a r e shown t o be s t i l l s a t i s f a c t o r y , i f an appropr ia te descrip-don is made toth$subassernbly s t e e l wrapper The buckling-dependent d i f fus ion c o e f f i c i e n t d e f i n i t i o n its found t o be re l evan t i n rhe case of sodiiln void experiment ana lys i s i n f a s t c r i t i c a l s .

Systematic assessment s t u d i e s have been performed of the r e l a t i o n of i n t e g r a l exseriments 2nd. aesigr: pazameter p red ic t ions a d r e l a t e d ;~r .certair : t ies In p a r t i c s l e r i r has Seen st'adied 3 e roc worLk /?,10, /, 3 e socium void reac- tivi:y e f f e c t and t i e reac-don r a t e s i m d sower) eistri3J-Aons.

I n Lkis csnnecrion, Lie r e l a t i o n c f desicr; p.xameters whick =e sA-r.nq. size-dependent (such a s power shape -perV~rSz+Aons) w i + k c r i L d c a l experiments, is being s y s t e n a t i c a l l y s t~adied . The p u - ~ o s e of a l l t hese works is t o def ine -he- fuzure d e t a i l e d experimental pr9gram on .?lASURCA, a f t e r completion of -he PACIIiE program.

2-3-4 3igh order rper?arSation methods ...............................

In Lie framework of i \ e a c t i v i t i e s r e l a t e d t o s e n s i t i v i t y metiiod e- lopment, new high order ?err7ar3ation f o m u l a t i o i s h a v e Seen used f o r :

- sh ie ld inq o p t i n i z a t i o n scudies - 5 e l cycle d a m assessment s?adies

So'Lh. works =e completed and have s:?own 5 e a p p i i c z b i l i r y of 5 e new high order t ec ix iques . For what concerns i i e f>ux r e ~ ~ n s ~ u c t i o n me*od, hasee on ha_*3c~.ics e+znsion, cile work bas been 2Esiled a d exemples r e l a t e d t o f - ~ e i a m a q m e n t a r e be ins sxudied.

The N i i so tope evaluazion w i l i be con2leted by Lie end of 1982. Furtiher evaliiarion work w i l l be performed i n the framework of the OECD

program f o r a J o i n t Evaluated F i l e . The N3-237 an8 3u-238 evalua t ions w i l l Se repor ted a t *the h t w e r ? meeting /1!,12/.

The adjus ted ve r s lon of t h e PROPANE f o m l a i r e has been kplemented; md i t s perfornances .?.re being v e r i f i e d with the aim of reducing tke p resen t SUPERPENSX s h i e l d desiqn u n c e r t a i n t i e s .

3 - LIGhT WATER PSACTOR TENSICS

airring t h e l a s t year , Saclay developments i n r e a c t o r phys ics were she(

t o Cie d e t a i l e a assessment of =he ?jEFTLm system f o r P h i c a l c u l a t i o n s : mainly two s e t s c f research have Seen Serformed. The f i r s c one was Sevoted t o s e l f - sh ie ld ing c a l c u l a t i c n s and Last one was intended t o improve tke c ross set*-ion l i b r a i r i e s used i n t h e 33 d i f f u s i o n c a l c c l a t i c n s . In a r e l a t e d f i e l d hprovement s t u d i e s had been erfo-nned f o r nodal d i f f u s i o n ca lcu la t ions .

A t C X L W J C ? ~ , experimental p o g r m s were sursued on c r i t i c ~ l e x p e r h e n m d on isradia-d h e 1 sanples .

P a r t of tke a c z i v i r y was a l s o 5 e v o ~ e d t o r e a c t o r surve51Lance technic and f n e l cycle p r o b l e m .

3-1 Theorer ica l s t a d i e s

The .APOLLO module of N3?TUNE r s e s a d e t e i l e d ~ e l f - s h i e i 8 ~ g calcula-iion based on reac t ion r a t e - t a b l e l i b r a r i e s allowing 99 groxp calcula-dons.

This procedure had been t e s ~ e d by comparison with ve-ry re f ined mxl'd- -;roup ca lcu la t ions (&out 10 000 qroups) and wi'ih Monte C a l o c a l ~ ~ i a t i o n s ;

a very good agreement has been o b u i n e d .

I3 +he same f i e l d , space dependent 6 i s " ~ i b u e o n s of Uranium and Plutoniur: had been obtained i n order t o improve t b e deple t ion ca lcular ion .

3-1-2 Few Group Cross Section L i b r a r i e s .................................

The d i f fus ion modules of N%Fl'L??E a e using c ross seccdon t a b l e s dependinr on parameters ( i . e . f u e l temperature, moderator densir-ies ... ) J n t i l now these t a b l e s were obminea performing a iXge number of asseinbly t r z n s p o r t c a l c s l a t i o n s (NEF?UNE! ; a new ?rocedure ha8 been designed and checked. This procedore i s now hplemented i n APCLLO and provides tiie general ized NEPLIS 3 . 0 . l b r a r i e s /13/.

These NETLIB 3.0 l i b r a r i e s a r e used i n ifye couple6 neutron k i n e t i c s m d - ,he-~al -hydraul ics x rans iec t aocide CilONCS d e s c + b e d a t t i e ANS :Cmesha Lake meetinc /14/ .

The e f f i c i ency f o r ?WR ca lcn la t ion of a l a rge number of T'-i- TLL- ,e element and nodal a p g o x h a t i o n ne<?ods were compared using t ? e framework of a s i n g l e coayt in ; . code. The r e s u l t s ~f --?is s tuey a r e submitted t o L?e next AN5 meeting/i5/

3-2 Experimental s t u d i e s

CRISTO I1

The CRISTO I1 programme has been completed a t the end of 1981. The l a s t p a r t of t h i s programme was concerning +he groblem of "gog condi-iions" i n d-y s torages . Two l a t t i c e s were scuciied :

- A s to raqe l a t t i c e obcained by simulation of four TWR s u b a s s d l i e s i! the t e s t zone with a gap of 8.lcm between t h e subassem5lies. Low dens i ty polyethylene i % 0 , 2 g / a 3 equivalent t o 0.26 i n water dens i ty) was used t o simula-ie ',re low dens i ty water condit ions.

- A regu la r l a c r i c e with 28x28 f u e l rods m d a square p i t c h of 1.86 cm. For t h i s one che polyethylene dens i ty was 0.14A g/cm3 equivalent t o 0.19 i n water dens i ty .

The r e s u l t s of tbe CXSTO I1 programme are s t i l l being analysed. 7 . - The p r i n c i p l e s of t h e xi f i f aeteminat ion method were given i n t h e l a s t

r epor t and a r e d e t a i l e d i n a paper presented, a t the ANS KIAMESBA LAKE meeting /16/

6k/] ?or regular lac-Lees the co ra l ';?cer'-'- -=,..T on kin? i s c lose zo 3.25 i ? C ! which allows 3 e s e r e s u i r s =a be use6 zs: e q e r l a e n t a l references f o r <ye ?hysicai va l idar ion of e-ll codes and associa ted i i 5 r a r i e s . Fcr s torage l a t t i c e s -ne luncer=ain=y on t i e e q e r % e n z a i l y dete-Mned kin5 i s larger, i n :he range 3.5 t o is 6k/k accordin5 =c che vzrious c o n f i ~ ~ r a z i o n s . :?.e discrepamzies wizh calcu- , -4. L c e d values obzainei w i 5 WOLLC-30T c 2 l c l a c i o n scheme are i e s s than 3 . 4 % except f o r Lie l a r c i c e s usinc: "grey" absor5ers ( s t a i n l e s s szee l j f o r which it .,

reaches : 5 .

CXISTO III

A second s e t of CXSTO 1x1 e x p e r b e n t s , a b i n g t o check t h e ca lcula t ion; of gadolinium poisoned conf igura t ions , was achieved a t t;le beginning of 1982. - -hese e e e r i m e n t s a e r e l a t e d t o the nse of cadoliniun a s so luble poison i n d is - so lve r ta".ks f o r reprocessirrg piar.ts. The t e s t zone was loaded wit& 801 TWR rods (3% en-ic.lnenr!: w i 5 i c 1.:5 cm scuare picz;?. The breeder zone was a l s o loaded w i t '

UOi rods but w i t ? a t i f f e r e n z enric.hent (3,53) /i7/.

Five poison contents were s tud ied , :bee w i t b Soron (0.3g/l , 2 g / l , m 3.5g/i! and two with gadolinium (0.75g/l ~ r d !.5g/l) . Two of zhe boron ccnte leaded t o -he sane c r i t i c a l s i z e a s Lye c a d o l i n i m confiqurazions.

Arelysllsof dye r e s u l t s w i i l include SucklFng dete- ina at ions f r m +-fie . . o w e r d i s t r i b u t i o n aeasaremencs &?d reaczlvli-y compc-iscns berweer, =?e S o r m &?E

g a a o l i n i m soisoning.

A new exse r i aen t is goizg on a t F O X , CAbELEON, which aims t o he check of ca lcu la t ions of various ai3sorSing c lusce r rod types. The r e a c t o r is loaded w i - ' -. a requIrar l a r t i c e of iJ02 rods (3.5% e n r i c b e n t ) w i t h a sqnXe ? i t c h s h i l c t o 'ci.: one of 17x17 Im t z e 5 e l assenbl ies 6 The cladSin9 5 i c k n e s s i s chosen t o obra iz :is s a e spec:m a s i n 2 ?m Fn power ogerazion.

Several absorbers w i i l be r e s t e d , Soron, Eafnium, Siver + indium i CaMum, Gadolinium, i n vrtrious contents . D i f fe ren t c l u s t e r configurat ions inclu- Sing 1 t o 2 4 absorSinq rods =e planned.

The absorber e f f i c e n c i e s 6-e dete-Wned from r e a c t i v i t y me as^-ernent ( c r 2 t i c a l s i z e , s c l & l e boron conzent, do.&ling t i ~ e , ... ) . F l u and power di& butions a l s c measures, including a ic roscop ic & s t r i S u t i o n s i n t \ e absorber roc wi ' l? a c t i v a t i o n f o i l s .

This exper inent i s slanned f o r w o u t 12 montlls and w i l l grobably be f a 1 lowed by the study of a low mocieratie l a t t i c e .

The C M E I Z O N p r o g r m e w i l l a l s o include some experiments aiming t o a more accura te dete-narion of t i e 3eff . Comparisons of s r a t i c &id d y n d c r e a c t i v i t y aeasurements i n a clean l a t t i c e w i l l be a a l y s e c using *he most accurate c a l ~ cu ia t ion methods.

This year the KINE3VZ 2 r o g r m e f o r l i g h t v a t e r r e a c t o r snys ics was s t i l l imi ted t o a few months and devoted t o r e a c t i v i t y measarements of small s a g l e s by the o s c i l i a t i o n ze&nique. After a d e t a i l e d study of gadolinium poisoned rods , which has shown no 2 a r t i c ~ l a r d i f f i c u l t y i n the t h e o r e t i c e l m a l y s i s of t h e r e s u l t a s e t of neasurements is goin? on with uraniun samples cf var ious 2 3 6 ~ contents (u? t o 1 . 5 % ) . Fhese measurements a r e a r t of the ;hysical s v ~ d i e s r e l a t e d t o t:le ,."- -=nium recycle s t r a t e g /18/.

A new s e t of Doppler experrments rs ~ i a n e d f o r 1983 i n order t o check .. -he low zempera-ijre prc5lems.

3-2-3 S-pent fue l Lralyses -------------------

Analyses of TISANG2 h e l samples were complered a t L?e beginning of i982. J e t a i l e d mass spec+:ometry measur-aents were performed on more 2.a 20 samples with bcrr-up ranging from 6C03 t o 38000 .Wd/T. The r e s u l t s a r e being an21ysed. Drel in i - nary conclusions were &awn f o r che main urani'um and g1utoni.m isotopes. The devi- a r ions between t i e o r e t i c a l and experimented values are q u i t e smaii but it a p p e x s 2

s l i g h t -end f o r t h e glstonium b u i l d up wit!? khe burn-up.

A new programme on 17x17 f u e l s was s t a r t e d tbis year. i n a f i r s t s t e p , samples L-e taken from a subassembly i r r a d i a t e d during two cycles i n FESSENHEIM.' I t i s planried t o go further b tAe f u t - x e w i ~ h f u e l s i r r a d i a t e d during th ree , four and, maybe, E v e cycles.

Spec i f i c i r r a a a t i o n s a r e a l s o going on i n tbe frame. of two developmenr, - programs :

- The use of ?G3 a s a bEnable poison f o r long cycles i n 3WR's. The w e - r imects performed i n ibe pas< yezirs have mainly concerned t h e i z i t i a l loading ( r e a c t i v i t y and sower d i s t r i b u t i o n e f f e c t s ) . I n order t o v a l i d a t e =he burn-up ca lcu la t ions of Gd poisoned f u e l s m i r r a d i a d o n was designed t o be r e a l i z e d i x the .QLCSINZ r eac to r . In the cen t re of -nis .QX type reaccor , it is ioaded a 23x13 i

rods sujassembly. The _soisone2 roes s u t i n four locations of the subassernjly m c CL? be I-aoved a r varioils szeps of tine i r r a d i a t i o n . Non d e s z r x t i v e examinations

- - . isgecc,-cme:x y) and 6es:ructive anzlyses are cerzned i n order t o k i n g a follow-ur; of t h e chances i.: i so rop ic comgosicions and o w e r ciistribuLiions. This i r r a d i a r i o n v i i l GO on durirg a L i t t l e more one year with 3 o r 4 iz termedia te exrninat ions Several gaciolinium contents with homogeneous o r heteregeneous loacings w i l l be s tudied in:-orcier t o g e t e q e r b e n t a l dara corresponding t o d i f f e r e n t gadolinium consumptiors.

- The recycle of reprocessed u r ~ r i u m is the aim of a second i r r a d i a r i o n e ~ e z i m e n t perforzed al.so i n the ESUSINE r e a c t o r , using rhe SEERWOOD device a l r e a e . used f o r a c t i n i d e cross sec t ion measurements /19/. In t h i s SEERWOOD 2 experimenr I+

samples a r e uranium o E 5 e s e l l s with d i f f e r e n t 2 3 6 ~ c o n t a t s (up t o 1.55). 25% I t is planned t o measure rhe U capc-xe with vazious se l f - sh ie ld inqs from mass spectrometry analyses of 'uie neptilniiun content . Results a r e e x p e t e d f o r the SegLnnii of 1983.

3-3 Core- s m e i l l a n c e tec.hnicpes

A l a rge e f f o r t i s devoted t o 2he imFrovement of s u x x e i l l a c e t e c : m i ~ e s of che PWR cores. Rnalysis of the neutron noise measurements r equ i res a physica l understanding of neut ronic , mechanic and the-ma1 , i . hy6raol ic phenomena /20,21/. l a r r i c u l z r app l i ca t ions was developed f o r s p e c i f i c problems such as the b a f f l e j e t t i n g de tec t ion and su rve i l l ance /22/ . T h e s n o i s e techniques &re a l s o applied f o r developing new i n s t m e n t a t i o n s and f o r ins t ance the l6ti f luc2aa t ions a r e used t o measure t..e r i n a r y flow r e t e /23/.

Works axe a l s o devoted t o t h e development of new incore de tec to r s ( yiPer- mometers) o r t o Lye improvement of e x i s t i n g devices (the-mocouples) .

The use of d i f f e r e n t tec:hn:ques f o r measuring the contzoi rod e f f i c i ency rs a l s o investigated.

j -4 Fuel cycle

The developmenr: of ex?erime?=al zecimicues f o r measuring -,ie brrz-up and - . = - s s i l e content of L-%R spenr f u e l s a t the inpu t c f :he reprocessing ? S a t was 2ursued. A paper on <:is top ic was presented a r 5-1 l a s r XEAC- neet ing . A new s e t of ex?e rbenzs w i l i srr-t a t 2. WG'E plan-, before the end o i 1982. It w i l l cover a wider v a r i e t y of r e a c t o r Eueis i n c l u S n g 3kX's ms Bw?.~. .hnaiysis of -jle 5 i r s t r e s u l t s has shown a good agre-nenz wit? reac=or p e B i c c i o n s a d d e s ~ - ~ c z i v e malyse! /24/.

Applicat ion of ca lcz ia red i s o t o p i z c o r r e i a t i o n s f o r -he inpu t balance de-2,minarion a t zhe reprocess ins p l a n t is now i n a rou t ine way /is/. N e w developments a r e being s t ad ied in the fzame of i n t e r n a t i o n a l sa fegwzds .

PEFERENCES

G. h i m = and a. G. T L E R ? eil a l , G . ii7FBERT e t a i , ( s e p t . 1982)

W . SCDOLTliSSXK e r

?ETiOT , ?aper r e s e n t e d a t ',?is meeting paper presented a t :his nee t ing paper t o be ?resented a r t h e ICWXSY? LU2 WS meering

e l , ibldelr D. C & W Y D , " y heating meascrenents i2 2 neteroge.?eous coz2lgurecion " >&per r e s e n r e d a 1 *is neer ing C. GiACO.?EPI e r a l , " ?.ecenz eevelc-,=enrs 2nd i=provemer.ts 2 -,?e c 0 C ~ systen ?or n e u u o n i c design c f fast breeders a t C a " ihidem C. COSINi e t a l , " Applica-con of a variar ional procedure f o r ~ r o u 3 Cross sec t ion app l i ca t ions " iSidern 3. 3ZNOIST, a p e r t o be presented a t -,?e K=KM2SFA ;AiW ANS neering i sept . 198; ??. S.2I;VATORES e r a l , ibidem C . G I A C O L T Z e t a l , " Contzci rod s z d i e s f o r lazqe WZ33 a: C A " _sresente2 a t t h i s s e e t i n g E . ?Om e t a l , Paper t o be p r e s e n t e t t he I n t e r n a t i o n a l Anrwe-7 Conference (Sept. 1982) 5 . D E m I E N e t a l , iSidem F. SA19 , Elaborat ion d 'un schema de c a l c i ~ l d e s s e c i o n s e f l i c a c e s tp?mt@pT des e i f e ~ s de con'ke r e a c t i o n dans un r eac ten r 2 i a u l ege re p r e s s u r ~ s i e . These 3e cycle O S A Y 1982 A. KAVZNOW e t J . J. ~ALTA;U) , The Neul;-on fineiiics and Themal 3ydraul ic Tx'an- s i e n t Computational Module of the N e p r ~ ~ e System : CRONOS, WS Topical Meetinr on Advance i n Reactor Physics and Core T h e n a l By&-aulics. A (1982 C. XAGXAUD, 3 .P :GP.INA3Tr 3.J. %U?L?S , On t5e r e l a t i o n s h i g between some Nadai schemes and 5 e T i n i t e Slement Metyod i n S t a t i c s i f f u s i o n Caicularions. ( t o be published)

A. SANTWA;IINA, L. - D E E E x 3 e r b e n t a l Qua l i f i ca t ion of t h e C a i c u h t € S u S c r i t i c a l i t y i n Eigh Densiry Fuei Szorage. ANS Topical Meeting - i C ~ ~ S I i A DXE (1982) A. SANTAMARLQA , CE~ISTO III a p e r b e x t s , >a?er 'jsesezzed it t h i s neering 3. DARROUZET e t a l , 3ecycl inq of the Xeprocessel Vranium i n PWRs-3C-9RUXSLLEE (1982)

M. DR4ROUZET e t a i , Deters inar ion Experinentale des Sect ions Zff icaces des Isotopes de Pu, Am, C n dans Spect re de Nentrozs de Riacteur A Eau. In?. Conf. on Nncieaz Data f o r Science 2nd Technology ANV3P.S (1982) ?. BERNARD e t a 1 , Quant i t a t ive Monitoring znd Diagnosis of French Pcv?lls I n t e r n a l StrTucYaes V i j r a t i o n s by *%core Neutron Noise LTC? AcceleromeEers I n a i y s i s . SMORV 3 - TOKYO (1981)

/ 2 1 / 3 . 3EWARD e t a i , Detection a d Monitoring of a o i l i n g i n 3WRs b y Incore NeurrOll Noise Anzlysis - SMORN 3 - TOKYO (1981)

/ 2 2 / 3. s E R N ~ e t 21, PWR Core Monitoring by Incore Noise Analysis - SXOm 3 - TOKYO (1981)

/ 2 3 / J.H. SOUCBT e t a l , P-NR Prima-ry Flow Xeasuraen t s by Corre la t ion Analysis cf ~ir-zoger. 16 ? l u c h a t i o n s - SMORN 3 - T3KYO (1981)

/ 2 4 / J . PIXEL , Dere-&nation 8u t a u de conbastion e t du b i l a n en i so topes f i s s i l : des assemblages irra&i@s 8ans l e s r eac teurs a eau ?ar des metbodes non 8es- ---uc=Lves. These a ,3xait-e.

/ 2 5 / A. CIAC3EIETTI e t a l , Asplicat ion des co r re la r ions isotopiques ca lcuiees 5w.s l a d e r e n i n a t i o n du b i l a n Z 'ent ree de l ' u s i a e de re%-air-ement de L A -3AGU"s. ( 2 S m A S p e c i a l i s t Meeting - PETTEN 1982)

REACTOR PHYSICS ACTIYITIES

I K THE

FEDEML REP'JBLIC OF GER%hT

Compiled

b Y

H. Kiisters

Kernf orschungszentrum Karlsruhe

General

In order t o improve the l i c e n s i n g procedure f o r PKRs, Kraftwerk Lhion has

launched the so-called Konvoi-Concept: four or f i v e nuclear p l a n t s a r e

designed t o be i d e n t i c a l a s f a r a s poss ib l e . A t p resent t h e f i r s t Konvoi,

comprising .Isar-2, B i b l i s C, Ervsland and Keckarwestheim-2, i s underway.

The advanced pro to type r e a c t o r s SAX 300 and THTR 300 a r e i n a f i n a n c i a l

c r i s i s . The manufacturing i n d u s t r y , the u t i l i t i e s and t h e Federa l S t a t e s

were asked t o supplement the e f f o r t s of the Federal Government.

I. REACTOR PHYSICS PROGRESS AT THE WCLEAR RESEARCH CEATER KARLSRLJHE

1. Experimental I n v e s t i g a t i o n s a t t h e Zero Power F a c i l i t y SNEAK

In SAEAK-12 f u e l r e d i s t r i b u t i o n experiments were performed and the cor re-

sponding r e a c t i v i t y e f f e c t s were measured and p a r t i a l l y eva lua ted . For

a x i a l l y symmetrical f u e l r e d i s t r i b u t i o n inc lud ing an i n v e s t i g a t i o n of t h e

e f f e c t of p l a t e o r i e n t a t i o n the ma te r i a l rearrangements were performed i n

up t o 16 c e n t r a l elements. For an asymmetrical slump-out c a s e (molten pool

experiment) the m a t e r i a l s were rearranged i n up t o 36 c e n t r a l elements.

The r e a c t i v i t y was measured r e l a t i v e t o normal f u e l d i s t r i b u t i o n , as f a r

a s poss ib l e i t was obtained by compensation with c a l i b r a t e d c o n t r o l rods.

For s u b c r i t i c a l i t y of more than 50 # the source m u l t i p l i c a t i o n method was

used.

Tne change-over t o v e r t i c a l p l a t e o r i e n t a t i o n i n the c e n t r a l 16 elements

i n genera l brought a r e a c t i v i t y r educ t ion i n the order of 20 d . Since t h i s

a p p l i e s f o r t h e re ference a s we l l a s f o r the rearranged conf igu ra t ions ,

t h e r e s u l t s of the m a t e r i a l r e d i s t r i b u t i o n experiments a r e q u a l i t a t i v e l y

unaffec ted by the p l a t e o r i e n t a t i o n .

'The keff f o r the d i f f e r e n t ma te r i a l conf igu ra t ions was c a l c u l a t e d using

2-dimensional S4-ca lcula t ions i n RZ-geometry. The r e s u l t s agree q u i t e well

with the measurements. Axial and r a d i a l r e a c t i o n r a t e t r a v e r s e s a l s o a r e

wel l reproduced, i n p a r t i c u l a r when the c ross s e c t i o n s a r e co r rec t ed f o r

c e l l he terogenei ty .

Dif fus ion theory y i e l d s moderate dev ia t ions f o r t h e t r a v e r s e s , but q u i t e

u n s a t i s f a c t o r y and non-conservative r e s u l t s f o r t h e r e a c t i v i t i e s .

A s epa ra t e c o n t r i b u t i o n t o t h i s meeting descr ibes the measurements and

t h e o r e t i c a l r e s u l t s more e x t e n s i v e l y / I / .

2. EK-Contr ibut ion t o BIZET Analysis

Concerning t h e jo in t UK-DEBENE BIZET-programme a n a l y s i s work i s now being

focused mainly on the s u b c r i t i c a l c o n t r o l rod s t u d i e s performed i n the

heterogeneous assembly BZD. The "core" reg ion of BZD comprised a c e n t r a l '

. breeder i s l a n d of 95 cm diameter - adopted from conceptual des'ign s t u d i e s .. of a heterogeneous SAX2 - surrounded by a f i s s i l e annulus (E = 24 %

Pu/Pu+U) of 50 cm th ickness . The core-height was 89 cm. As usual , t h e modi-

f i e d s u b c r i t i c a l mult ipl . icat ion technique was employed on the b a s i s of t h e

inhe ren t spontaneous f i s s i o n of t h e Pu-fuel. 3D s y n t h e s i s d i f f u s i o n calcu-

l a t i o n s using c e l l he t e rogene i ty c o r r e c t e d KFKINR cross-sec t ions condensed

t o 4 energy groups, yie1.d C/E-values i n the range of 1.00 t o 1.06 (with

T u t t l e y i e l d s ) - somewhat lower than i n t h e preceding homogeneous assem-

b l i e s . ?he reason f o r t h i s behaviour i s p r e s e n t l y being i n v e s t i g a t e d .

3. The Formation of Pu236 i n PVRs

Due t o the amount of Pu236 i n plutonium from LWRs, s to red plutonium w i l l

show i n t e n s e high energy gamma r a d i a t i o n from Th208 i n the decay chain of

Pu236. This e s p e c i a l l y might be important f o r s to red mixed oxide f u e l

elements f o r f a s t r e a c t o r s to a l e s s e r degree a l s o f o r f u e l t o be recycled

i n thermal r e a c t o r s .

In LWRs t h e formation of Pu236

s t rong ly depends on the spec-

trum averaged (n,2n) c r o s s sec-

t i o n s of Kp237. Due to t h e

threshold of t h e c r o s s s e c t i o n

around 7 MeV a proper represen-

t a t i o n of the high energy p a r t i i of the neutron spectrum both

. '/ - 2' ! i n f a s t and thermal r e a c t o r s

Pu 236 I - i s important . Experimental T r l n a 2 - P e l l e t s

i i Pu236 concent ra t ions from ~ i

+ E x p e r i m e n t

I t i TRINO p o s t - i r r a d i a t i o n analy-

Burn-ui, - G u e l l u i s i s were compared kYth ca l cu la -

i 30-,; 6

1 2 1 6 2 o 2 a 3 a t i o n a l r e s u l t s /2/ a s shown i n

Fig. 1.

Fig. 1: Pu236 Formation i n TRIN02

With the -Karlsruhe KEDhK d a t a

a s l i g h t overes t imat ion of the

Pu236 content was obtained and can be considered a s pes s imis t i c e s t ima te

of the measurements. Because t h i s Pu236 content i s h igher than t h a t from

previous c a l c u l a t i o n s , the corresponding s h i e l d i n g problem has t o be re-

i n v e s t i g a t e d .

Nuclear Data f o r Fuel Cycle Analysis and t h e i r Va l ida t ion

A new eva lua t ion of nuclear da ta f o r t h e i s o t o p e s Am241, Am242m, Am243 and

Cm244 i s completed. A c r i t i c a l review of the Am241 da ta was a l r e a d y per-

formed wi th in t h e frame of t h e j o i n t European/Japanese da ta f i l e JEF.

Recent d i f f e r e n t i a l

measurements f o r the ( n , y ) c ros s s e c t i o n of Am243 /3 / show a very good

agreement with the t h e o r e t i c a l l y p red ic t ed va lues of t h e KEDAK evalua t ion .

2L3~rnln.yl - KEDAK 1981 -- ENDFIE-V

W~sshak+Kappeier 1982: 50 rnm flight path

Fig. 2: Recent Am243 (n ,y ) measurements and

comparison wi th KEDAK and ENDFIB-V

To v a l i d a t e t h e data a l s o by i n t e g r a l experiments , a c r i t i c a l d i scuss ion

of measured resonance i n t e g r a l s was performed and compared with t h e o r e t i -

c a l r e s u l t s from var ious eva lua t ions / 4 / . The r e s u l t s a r e given i n the

fol lowing t a b l e s .

TABLE I Capture resonance i n t e g r a l s from d i f f e r e n t eva lua t ions

KEDAK-4 1452 280 1847 637

UKNDL 1415 1846

JENDL 2 0 i 593

ENDF/B V 1420 286 1818 595

TASLE 11 F i s s i o n resonznce i n t e g r z l s from d i f f e r e n t evz!uations

KEDAK-4 11.6 1629 G.4 16. 1

UKKDL 15.02 : a; -.,a

JENDL 1575 17 .8

ENDF/B V 13.4 1886 6.15 18.7

For a c t i n i d e i s o t o p e s , due t o t h e presence of s t rong subcadmium reso-

nances, the measured resonance i n t e g r a l s a r e very s e n s i t i v e t o the e f f ec -

t i v e cadmium cutoff energy. For Am241 d i f f e r e n t eva lua t ions a r e c o n s i s t e n t

l d t h each o the r and with i n t e g r a l da t a except t h a t of Zhuravlev e t a l . /5/.

For Am242m the data bas i s i s poor but the importance of t h i s i so tope i n

burn-up c a l c u l a t i o n i s low. For Am243 t h e r e i s a 20 % underest imation of

the capture resonance i n t e g r a l v a l u e s , c a l c u l a t e d from d i f f e r e n t i a l d a t a ,

compared to those measured i n a r e a c t o r . Sew neasuremencs seem necessary

t o reso lve t h i s discrepancy. For Qn244 t h e data a r e i n good shape. Tne

recent eva lua t ion of d i f f e r e n t i a l da ta (KXDAK-4) g ives about a 5 % higher

value f o r the capture resonance i n t e g r a l of Cn244. This value i s supported

by the r ecen t measurement of Gavrilov and Goncharov / 6 / and the pos t i r r a -

d i a t i o n f u e l a n a l y s i s c a l c u l a t i o n s .

The i s o t o p i c composition of spent f u e l can a l s o be used to check the da ta

r e l evan t i n burn-up c a l c u l a t i o n s f o r thermal r e a c t o r s . The measurements

a r e performed with a-spectroscopy and mass a n a l y s i s . Am241 i s not wel l

s u i t e d f o r a-spectroscopy, because t h e a-peaks a r e shadowed by those of

Pu238, which i s generated v i a hQ237(n,y) and subsequent 8-decay, and v i a

a-decay of Cm242; i n a d d i t i o n 75 % of the Am241 a t the time of a n a l y s i s

(about 3 yea r s a f t e r d ischarge) i s due to Pu241 decay and cannot g ive a

r e l i a b l e check on the Am241 c r o s s s e c t i o n .

Recent p o s t - i r r a d i a t i o n measurements f o r the content of Am241, Am243 / 7 /

and Cm244 /8/ i n spent PkrR f u e l were based on the i s o t o p e d i l u t i o n tech-

nique. h e y give e x c e l l e n t agreement with KFK c a l c u l a t i o n s . This com-

par i son i s demonstrated i n Fig. 3, Fig. 4 and Fig. 5.

A i N : g ; t u i

I A m 241

K W O 121

b I s o t o ~ e D i l u t i o n A n a l y s i s

15 8 1 Burnup

10 zqii? 1 8 22 26 3 0 35 38

I I

Am 243

K W 0 1 2 1

A " - s ~ ~ c l l ~ m . t r ~

b Iso tops D i l u t i o n A n a l y s t s

10- 1 8 2 2 2 6 3 0 3& 3 8

Fig. 3: Ihe Am241 content Fig. 4 : The Am243 content

i n spent PWR f u e l i n spent PWR f u e l

C m 2 L L

K W O 124

- 30 K O R I G E N

Experiment l l so topc D i lu t ion

2 0 . A n d y s i r l )q81

10..

1 8 2 2 2 6 30 3 4

Fig. 5: The a 2 4 4 content i n spent PWR f u e l

The f a s t energy range w i l l be i n v e s t i g a t e d next. Prel iminary r e s u l t s show

a s a t i s f a c t o r y agreement.

5. Studies on Advanced P res su r i zed Cater Reactors (Tight L a t t i c e Cores)

Design c a l c u l a t i o n s have been performed f o r a movable seed/blanket con-

c e p t , a f i x e d module concept with c o n t r o l rods , and a homogeneous design.

The va r ious r e s u l t s a r e analyzed and a c r i t i c a l d i scuss ion on advantages

and disadvantages of t h e s o l u t i o n s among each o ther and compared to a PWR

i s i n progress . This e f f o r t i s done i n coopera t ion with Kraftwerk Union.

Basic i n v e s t i g a t i o n s have been performed on the accuracy of data and

methods f o r the c a l c u l a t i o n of t i g h t l a t t i c e p l u t o n i m c o r e s ; a success fu l

comparison with experimental r e s u l t s / 9 / , a v a i l a b l e i n the l i t e r a t u r e , was

made. Experiments, underway a t E I R i n Wiirenlingen, w i l l f u r t h e r he lp t o

c l a r i f y the adequacy of t h e t h e o r e t i c a l t o o l s . Many s e n s i t i v i t y s t u d i e s

were performed on t h e in f luence of design pa raae te r s a s e.g. plutonium

composi t ion, ref l e c t o r , c o n t r o l rods e t c . on the value of the coolant void

r e a c t i v i t y / l o / .

References

/1/ F. Helm, G. Eenneges: Erogress i n the Evaluation of SKEAK-12A

Program, Separate c o n t r i b u t i o n t o t h e 25th hrEACRP Meeting 1982

/2/ K.W. ir'eise, U. F i sche r , B. Goel: Analysis of Neutron Cross Sect ions

f o r the Formation of Pu236 and Co58,60 i n both Thermal and Fast Reac-

t o r s , Int. Conf. hzlcl. Data f o r Science and Technology, 6 - 10 Sept.

1982, Antwerp, paper A-20

/3/ K. Wisshak, F. G p p e l e r : Neutron Capture Cross Sect ion of Am243 i n

t h e Energy Range 10 t o 250 keV, In t . Conf. Nucl. Data f o r Science and

Technology, 6 - 10 Sept. 1982, Antwerp

/4/ B. Goel, U. F i scher : A C r i t i c a l Review of Resonance I n t e g r a l s and

Post I r r a d i a t i o n Fuel Analysis f o r Important Isotopes of Am and Qn,

In t . Conf. Xucl. Data f o r Science and Technology, 6 - 10 Sept. 1962,

Antwerp

/ 5 / K.D. Zhuravlev, K.1 . Kroskin, A.P. Uje tv jer ikov: A t . Energy (USSR),

39 (1975) 285

/6 / V.D. G v r i l o v , V.A. Goncharov, Sov. A t . Energy 44 (1978) 274

/7/ B. Ganser: Analyse und e i n Gewinnungsveriahren des Americims in:

Kernbrennstoffzyklus des Druckwasserreaktors, EK-3380 ( J u l i 1982)

181 M. Wantschik: Bestimmung der Cur imbi ldung i n Leichtwasserreaktoren

und Vergleich m i t Berechnungen , KfK-3316 (Psrz 1982)

' 9 H. D. Berger, C. Broeders, A.W. Rowe, N. Schatz : tiberpriifung der

Berechnungsverfahren f i i r enge Reak to rg i t t e r von F o r t s c h r i t t l i c h e n

Druckwasserreaktoren (FDWR) an experimentel len Anordnungen, EK-3389

(1982)

/ l o / C.B.M. Broeders: ?;eutronenphysikalische Untersuchungen zu engen

H20-moderierten Kernanordnungen, Proc. of Jahrestagung Kerntechnilc,

p. 15, 4 - 6 Mai 1982, Idinnheim

11. REACTOR PHYSICS ACTIVITIES AT KRAFTiLTERK URXON

1. Compuratlonal Merhods for LWR Analysis and Thelr Valldatlon

Gamma Scan Postcalculation of e Coarse Mesh Grid for - - - - - - - - - - - - - - - - - - - - - - - - - - 117 Fuel Elements in KIP1 (BhC2) - - - - - - - - - - - - - - -

In 1980, 117 fuel elements of the KIP1 reactor have been Gamma

scare5 Curing the one year's outage 4 GWC/t eqosure state. - r ? Each o~ ir axiai positions was measured from the four edges by

rotating ;he fuel element in the fuel storage pool. The whole

s?ec--;>- \,:as covered cp to 2 GeV jut only the k14' 2nd

Pr 1 4 lines were aorth-while to Se an~lysed.

The postcalculations were per_"ormed with the KbW standard design

methods. These include evaluation of tkree group macroscopic

cross sections for the fuel elements ( ~ ~ 1 had a scatter loading . . of four mfferent enriched fuel elements in the first cycle)

dependent on void content and exposure, as well as fine mesh

diffusion theory flux solution in 2D for the fuel and coarse mesh diffusion flux solution in jD for the reactor nodes. The

jD solution is iteratively cougled with Dix void calculation.

and Pr lW coarse mesh distributions have been dccuuaulzted

through adequate time steps within the fuel cycle.

The results show good agreements in the axial as well as in the

radial directions (Figs. I and 2). The mean square error of the

fuel bundle power distribution is 4 %. This is not large re- . garding the fact that there are four very different U235 enrich-

nents in the core, an5 the coarse mesh method is only 1 '?/2 . ' I * ' g x u p c ~ ~ u s i o r , theory.

m. m e results show that the present design methods are not only

snfficient for honogeneous core loading but also for the present

four emiched cores.

J ' , 0 I I

bo t tom O X ~ Position top

1 K K ? 1 h a s c a n 1W Uean axial Ba 140 Distribution (111 fue l eierentr) Ccmparison with R S 3 D and Process Cmputer

I(nbr*lhb,

Fiq.2: K I( P 1 bw Scan 1980

Scatter P l o t o l Fiadlal BalYi RS3) versus l l c a s ~ n m t

I , - '

r . s=:velent Ro~ogenized Reflector C-oss Sections

- 1- Cesign aid anal)-sis of nodern light - weter reac-iors with nodal

nez'nocis the desc-lptlon o_' rezlec-ior 2l-olserties can be improved

by utiiizing the homogenizatior~ scheme of 'equivalence theory'

/I/. The main feature of this theory is to conserve a set of

integral qumtities such as reaction zates, surface currents

and fluxes for each node. As a special application the proce-

ak-e was used for descriSing the interacxion of core aid reflec-

%or as shown in Fig. 3 . Reference solucions were produced by . . -- bil~ng ,- e~licitly irto accomt the geometricel structure of

L.

a Lne shroud.

homogenized r e f l e c t o r

\ F i g . 3 Octant R e p r e s e n t a t i o n o f a PkFi v i t h Homgen ized

Assembly- and R e f l e c t o r Nodes

Tab. 1 illustrates that foz a wide range of reactor stztes

- differing with respect to boron concentrations znd control roci configurations - the equivalent reflector model is

superior to the conventional albedo concept which m&es use

of predetermined inconing - to-outgoing current ratios at the core-reflector interface.

1 c o n t r o l m d 1 con i . I c (pn! 1 t i n ) /

1 . 1 : C o n t r o l Rod Ccnfigurat~onr o f a PW, EU

3. 2es;sonse Matrix Representation of LM? Reflectors

3ecause of the cost 2enalty associated with an emlicit c ~~eatment ,, of the reflector 2nd since information about dif-

fusion theory flux shapes in the reflector is rarely needed,

there is an incentive to solve -ihe group diffusion equations

for a reactor 5y imposing a homogeneous boundary condition at the core-reflector interface. At KhTJ an extension of such

a procedure is being considered.

The representation of 2 PWIi radial reflector by precalculated

response matrices A g'g' (g,gl energy group, M , M 1 face indices M , M ' ' of core-reflector interfaces {M) 1 yields the correct nodal

incoming current

J I n = I / A g t g ' ,out

Mtg M ~ M ' ~ : g ' g1 M'EIMJ

on each c o r e - r e f l e c t o r - i l l t e r f a c e , eve- ic trasient situations,

where the proporties of the reflector may change significmtly-

srovided - the matrices are properly paranetrized. Response matrices

fo? 2 t ~ i c e l 1300 PTv,i, PhrP, were calcclated with the aid of the -

noCal code FXSPOX /2/ using diffusior theoq. The precalculated matrices were used afterwards ill the nodal cocie IQSBOX / 3 / . The

normalized power distribution of a statiocary stuck-rod

configuration calculated with IQSBOX using response matrices for the PWR-reflector is given in Fig. 4 in comparison with

a reference solution by MXDIW! /4/ which models the reflector-

geometry exactly in this case.

Tke remaining differences are due to different representations

of the transverse leakage approximation in both models / 7 / . They should disappear if the response matrices are allowed to carry

additional information about transverse flow while.they are

generated. The response matrix concept is now under investigation

ia transient calculations.

2. Introduction of Gadolinium in PWR1s

The increasing interest in extended fuel cycles arrd low-leakage

fuel management leads to the necessity of u-tilizing burnable

poisons in FhZ reloads aiso. The adnixture of Gd 0 to the fuel 2 3

of some fuel rods of a fuel assembly (PA) has benefits over

other forms of fixed burnable absorbers:

- almost complete burnup of poison

- no parasitic absor2tion associated with additional cladding ' required for other absorbers

- no displacements of fuel rods or water -

- no additional waste ~angement problems.

The intl-oductior, of gadoiinium in commercial PWR's consists . . of e gadolinia-~oxsor,edF?k m d first core design and the analy-

sis of low-leakage h e 1 management schemes /5/. For the standard 16x16-20 FA two prototype (3.1 and 3.5 w/o U235) gadolinia-

poisoned reload FAA's (8 Gd-rods per F-4) have already been laid

out aad setur, to cover gadolinia concentrations in the range

of 4 to 7 W/O Gd203. These concentrations are required in gado-

linia-poisoned first cores in order to guarantee similarly bene-

a ficial nuclear properties according to local power density and

depletion behaviour as the well known fist cores with borosili-

cate /6/. The gadolinia-bearing rods contain a lower U235-enrichment than the unpoisoned. rods of the FA, thus 'avoiding the

build-up of higher fuel temperatures in these rods due to

reduced thermal conductivity.

In cooperation with the German utility RWE, an irradiation program for the mentioned Gd-prototme FA'S has been started

in the Biblis-B 1300 I'We power plant. This program was initiated

with a view to the verification of calculational methods

,-, -- ii"&-z/?EC:L%) u s e ~ for core and file: assembly design and fuel - . . . , macagement pnr2oses. In per;;cular zne de2letion behaviour

- . of tke gadolinia-poisoned rocis zrd ?A's w i l l 3e investigated -. carefni;y by performance of b,-scan-measmemerits and isotopic

xnalysis of the irradiated fuel rods of the Ed prototype-Fk's.

3. Gamma-Sensitive Traversing In-Core Probes

Tower distriktions in boiling water ~eactors (BILR's) are

calculated by the process computer -sing flux measurements C Lrom traversing in-core probes (TIP'S). The TIP'S are inser- ted into gu;uide tubes between t5e fuel bundles. From results

- m-- 01 ~ i r evaluations the local power r a g e monitors are cali- % - . C A ~ ~ Y _ G u - ~ wkich are used fcr continuous -,la_nt mcnitoring ?ad for

inxiz TC power allocation assessments.

y,? -..c - current TIP system Ciesign consists of ior?ization chambers sensitive to thermal neutrons. These detectors are sensitive

to tolerances which can be attributed to sensitivity of the

detector response to water ga;? varia-;iocs a d detector posi- , . -c:onicg. This may result in asymnetrlc in-core readings for

core locations where the actual power distribution is symme-

tric leading to conservative thermal-hy&raulic liollts which tend

to reduce reactor operating flexibility.

The spatial positioning problem of thermal neutron TIP'S can be soived by using gamma-sensitive TIF"s which respond to

prompt and delayed gammas because the g m a flux distribution

is more uniform in the water gaps. Thermal neutron TIP'S have

Seen replaced by gunma-sensitive traversing in-core probes

(TIP'S) at two operating boiling water reactor (BUR) plants (:I%%!; cycle-6 m d KKP, Cycle-2). Significant reductions in

the difference between detector readings at symnetric core

locations were observed which appeared directly as improved

plant o~erations margins.

4. Investigations of small leak accidents in PWRs for local

positive reactivity feedback situations

The void-reactivity coefficient of a PWR varies relatively

strongly during burn-up, because it is very sensitive to the

boron concentration in the coolant. The void coefficient can

be positive locally at high boron concentrations, i.e. at

start-up conditions. The relations between the critical boron

concentration, start-up power load, coolant temperature coeffi-

cient and coolant density coefficient, the worth of shut down

rods and the maximal pe-nissible fuel temperature were analysed,

A critical boron concentration could be derived, with which it

a is possible to localize during the start-up procedure (reactor

power below rated power) permissible and non-permissible states

regarding the coolant temperature and density coefficients. It

is thus guaranteed for any leakage accident in the primary loop

that the fuel temperature during the neutron flux transient

remains below the temperature at rated load; thus the conditions

for emergency cooling are not any worse than for operations

at normal rating,

The control rod worth parameter is thereby not a parameter which

affects substantially the control of accidents involving pressure

relief.

/2/ B. Niiller

unpublished

/4/ -- K.R. Xagner, E. Fi-nrremem~: $Lo Koebke, ?I.-J. Winter

Validatyon of the Nodal E q z n s i o n Method and t h e Depletion

2 r o g r m ,YEDILT-2 by Benchmark Calcula t ions and Direct n - bonparisor with ~ x r e r i m e n t s :

Atomkernenergie 30, 129 (1977)

W. B 6 h and I:. -D. Kiehlmam

"UO -Gd,O Burnable Poison Reac t iv i ty Control i n 2 r 3

mms , " Proc. I n t . WS/ANS Conf. on New Di rec t ions i n

Nuclear Energy with Emphasis on Fuel Cycles;

Vol. 40 ,p . 185, Brusse l s , fizril 26-30, 1982.

/6/ H.-D. Kiehlmann "C-adolicimoxid a l s abbrem-Sarer Absorber i n 18x18-24-

Xrs tker r des 1300-MbJe-Druck~asserreaktors"

Tagungsbericht d e r Jahrestagirng Kerc-cechnik 1982, p.23,

Mannheirc, May 4-5, 1982

111. REACTOR PHYSICS ACTIVITIES

AT THE UNIVERSITY OF STUTTGART ( I K E )

1 Adius'aent of N e - ~ t r o n Mul t ig roup Cross S e c t i o n s w i t h E r r o r

Coveriance Mat r ices t o D e e w P e n e t r a t i o n I n t e g r a l E x ~ e r i m e n t s

( G . Hehn, R.-D. Bachle , G . P f i s t e r , E. Mattes ; I K E ;

and W. Mat thes; CCR Euratom)

Rad ia t ion damage and s h i e l d i n g problems r e q u i r e s p e c i a l m u l t i -

group d a t a l i b r a r i e s f o r t r e a t m e n t o f neu t ron and gamma r a d i a -

t i o n i n deep p e n e t r a t i o n o f m a t e r i a l s . The s p e c i a l f e a t u r e s

o f group d a t a f o r r a d i a t i o n s h i e l d i n g have e v e r p r o f i t e d by

measurements o f i n t e g r a l exper iments . Modern ad jus tment o f

group c r o s s s e c t i o n l i b r a r i e s can make use o f t h e f o l l o w i n g

impor t an t advantages :

a ) t h e a v a i l s b i l i t y o f comprehensive s e n s i t i v i t y s t u d i e s showing

t h e d e t a i l s o f d a t a r equ i r emen t s needed

b ) t h e a v a i l a b i l i t y o f e r r o r cova r i ance in fo rma t ion w i t h c o r r e -

l a t i o n a c r o s s energy range and r e a c t i o n t y p e , and l a s t n o t

l e a s t

C ) t h e a v a i l a b l e r e s u l t s o f c l e a n deep p e n e t r a t i o n i n t e g r a l

exper iments des igned f o r s i n g l e m a t e r i a l s i n n e a r l y one-

d imens iona l geometry.

Mainly because o f t h e q u a d r a t i c a d d i t i o n r u l e o f e r r o r s , t h e

b i g g e s t e r r o r c o n t r i b u t i o n dominates ove r a l l s m a l l e r p o r t i o n s

d r a s t i c a l l y , s o t h a t t h e need f o r ad jus tment of group c r o s s

s e c t i o n s and e r r o r cova r i ance m a t r i c e s is conf ined t o v e r y

few e lements w i t h i r o n a s the most impor t an t one. Within

t h e modular code system RSYST an i t e r a t i v e ad jus tmen t proce-

du re ADJUST-EUR has been e s t a b l i s h e d , u s i n g one- and two-

d imens iona l S - c a l c u l a t i o n w i t h l i n e a r p e r t u r b a t i o n t h e o r y . N

The deep penetration iron experiment ASPIS/Kinfrith was reeva-

luated with new error covariance dzta availzble and first

measur~wnts of the integral experiment EUFLWOS/Ispra have

been used additionally.

The data adjustment is performed in 100 neutron groups and

supplied with the appropriate covarimce matrices in the

EUIUIB-5 library for coupled neutron and g m a calculations.

The iron integral experiments'were evaluated with a special

superfine Sroup structure between 3 EeV and 10 keV tocover

the neutron streaming along the cross section minima in the

large iron blocks. We got there a proper resonance weighting

for the EUIUIB group data locally dependent from the pene-

tration depth. The adjustment needed for the group data can

be explained as correction to the weighting function primarily,

and secondly as an effective reduction of energy degradation

by the inelastic scattering process of iron.

2 IKE Contribution to the KEA Shieldinq Be?chmark for a PWR

( G . Kicherer, G. Rehn)

The second interconparison of a PW3 shield calculation within

the NEACRP was initiated to show, where the advanced require-

ments of reactor safety and radiation protection are met and

where further improvements are still needed. ,The aim was to

study the effects of nuclear data uncertainties in a benchark

exercise comparing the following quantities:

a) shielding target quantities like radiation dose rates, acti-

vation rates, neutron damage production, and gmxa heating

rates were calculated for intercomparison,

b) cross section sensitivity studies were performed for the

main target quantities and finally

C) a complete error malysis was made using error covariance

matrices.

The codes AKISN, SWANWCE and SENSIT were a p p l i e d f o r e r r o r

a n a l y s i s i n t h e mu l t i g roup s t r u c t u r e of EURLIB. The 30 group

COWILS cova r i ance i n f o r m a t i o n , based on ENDF/B-5, was ex-

tended t o t h e 100 group s t r u c t c r e o f EUilLIB. S p e c i a l e f f o r t

was devoted t o approximate t h e u n c e r t a i n t y o f gamma p r o d u c t i o n

and gamma c r o s s s e c t i o n s f o r d e r i v i n g t h e u n c e r t a i n t y t o t h e

gamma t a r g e t q u a n t i t i e s of i n t e r e s t .

3 ~ r i t i c a l i t v c a l c u l a t i o n s f o r t i g h t l a t t i c e s ( Q i a n , Yuan-Chun)

ENDF/B-IV/V c r o s s s e c t i o n d a t a and neu t ron p h y s i c s methods ava i -

l a b l e a t I K E have been a p p l i e d t o c a l c u l a t e m u l t i p l i c a t i o n con-

s t a n t s and r e a c t i o n r a t e s of expe r imen ta l c r i t i c a l a s s e m b l i e s

w i t h t i g h t l a t t i c e s . I n t h e f i r s t s t e p heterogeneous c e l l c a l c u -

l a t i o n s 21-e a p p l i e d i n t h e resonance r e g i o n w i t h 8500 energy

groups. Resonance a b s o r p t i o n i n t h e unreso lved r e g i o n i s t a k e n

i n t o accoun t by t h e f - f a c t o r concep t . An i n t e r m e d i a t e g roup

s t r u c t u r e c o n t a i n s 1 7 1 f a s t and 126 thermal g roups . The f i n a l

c r i t i c a l i t y c a l c u l a t i o n s a r e done i n 60 groups w i t h a 1-D

SN-method. The r e s u l t i n g m u l t i p l i c a t i o n c o n s t a n t s f o r two

t i g h t l a t t i c e s t u r n o u t t o Se: k e f f = 1,003 and 0 ,9993. The

d e v i a t i o n s of c a l c u l a t e d r e a c t i o n r a t e r a t i o s from exper imenta l . "28 ones a r e g e n e r a l l y w i t h i n a few p e r c e n t , e x c e p t f o r d

4 Thermohydraulic feedback i n embedded f i n e mesh c a l c u l a t i o n s

('#?.I). Erha rd , J. Elzrnann)

I n o r d e r t o perform a d e t a i l e d n u c l e a r s t u d y i n t h e v i c i n i t y o f

t h e topmost end of a c o n t r o l e lement i n a BWR t h e s o c a l l e d LUPE-

t echn ique was developed. Because of t h e s t r o n g c o u p l i n g between

f l u i d d e n s i t y and power g e n e r a t i o n i n t h e f u e l e l emen t , an

i t e r a t i v e c o r r e c t i o n between t h e n u c l e a r and t h e thermohydrau l ic

c a l c u l a t i o n s i s nes sesa ry . The re fo re t h e n u c l e a r code LUPE was

coupled wi th t h e ve ry complex subchannel a n a l y s i s COSRA I11 C .

I n o r d e r t o reduce t h e cost of t h e thermohydrau l ic c a i c u l a t i o n s

a ve ry s imple one-dimensional thermohydrau l ic model was used

t o g e t h e r w i t h LUPE.

The d i f f e r e n c e s between t h i s s imple v e r s i o n and LC'PE-COBRA I11 C

c a l c u l a t i o n were i n v e s t i g a t e d .

I n a d d i t i o n a s tudy was performed t o what e x t e n t a s u b d i v i s i o n

of t h e cons ide red r e g i o n i n t o s e v e r a l r e g i o n s , each one t r e a t e d

.with t h e one-channel model, i n f luenced t h e r e s u l t s o f t h e coupled

c a l c u l a t i o n s and t o what e x t e n t c a l c u l a t i o n s w i t h t h i s s u b d i v i s i o n

approached t h e LVPE-COB= I11 C r e s u l t s . 0

5 A p o s t e r i o r i e v a l u a t i o n o f t h e coarse-mesh c a l c u l a t i o n

r e s u l t s i n b o i l i n g wate r r e a c t o r dynamics

(M. Havranek)

The i n c l u s i o n of t r a n s p o r t e f f e c t s i n t h e 3 D a n a l y s i s o f t h e

l o c a l power d e n s i t y i s under way. F i r s t t h e t he rma l neu t ron

f l u x w i t h i n t h e r e g i o n c l o s e t o t h e c o n t r o l b l a d e s i s c a l c u l a t e d

wi th t h e SN-code TWOTm. Then t h e d i f f u s i o n c o e f f i c i e n t s f o r a l l

f i n i t e - d i f f e r e n c e meshes w i t h i n t h e r eg ion a r e de te rmined . I n

do ing s o t h e c e n t e r e d d i f f u s i o n t h e o r y e q u a t i o n s a r e so lved f o r 0 d i f f u s i o n c o e f f i c i e n t s w i t h t r a n s p o r t f l u x e s which have been p u t

i n . Thus a l l r e a c t i o n r a t e s remain p re se rved and t h e 3D-code

LUPS r e f l e c t s t r a n s p o r t phenomena i n t h e r e g i o n s b e i n g concerned.

The thermohydraul ic-coupled and t r a n s i e n t 3D-code LUPE i s aimed

a t g e t t i n g implemented i n a system o f computer ized c o r e s u r v e i l l a n c e z

To t h i s purpose a f a s t runn ing v e r s i o n of LUPE is b e i n g deve loped .

The f a s t LUPE i s s u b s t a n t i a l l y a m u l t i d i m e n s i o n a l - i n t e r p o l a t i o n

code o p e r a t i n g on a p r e - c a l c u l a t e d da ta -base . Thus t h e f a s t LUPE

w i l l c o n t r i b u t e t o t h e o p t i m a l p r e d i c t i o n c o n t r o l f o r e f f i c i e n t

p l ann ing o f r e a c t o r o p e r a t i o n .

I TALP

"REACTOR PWSICS ACTIVITIES IN ITALY"

(October 1981 - September 1982)

R. Martinelli, ENEA

1. FAST REACTORS

Most of the LMFBR Physics activities in Italy are carried out

in the framework of the Research and Development agreement between

ENEA (formely CNEN) and the French CEA. The main areas of cooperation

have been: interpretation of core and blanket integral experiments,

reactor dynamics, cross-section evaluations and adjustments.

1.1. Core Integral Experiments --------- ------ -------- The comon CEA-DEBENE-ENEA programme "RACINE" in the critical

facility MASURCA (Cadarache) has been continuing, even if with some

modifications with respect to the original planning ill.

Following the validation of methods for the prediction of sodium

void reactivity distribution in large homogeneous and heterogeneous cores

-which was completed in 1981 / 2 / - an assessment has been made of the accuracy of control rod calculational methods for commercial-size LMFBRs.

In this assessment / 3 / , experimental bias factors (and associated

uncertainties relating to extrapolation) have been derived mainly from the

experience gained from experiments made on Superphenix-type absorbers in

the course of the "?RERACINE/RACINE" programme.

The programme is presently focused on subcritical measurements

with static (modified source multiplication) and kinetic (rod-drop)

methods 141. Negative reactivities are derived from the responses of

neutron detectors placed in the core and in the radial blanket, by intro-

ducing calculated corrections for variations of detector efficiencies.

Four new configurations have been tested at ENEA (Casaccia) in

the programme "NEFERTITI" 5 , 2 parametric experimental stuciy of neu-

tron propagation in fast reactor blanket regions fed by the fast source

reactor TAPIR0 through a fissile spectrum adapter. The present config-

urations are driven by a softer spectrum with respect to the earlier

ones.

The main difference between the calculation-experiment compar-

isons relating to the two sets of experiments consists in an inversion

of trend for the spectral index Fission U-238/Fission U-235, which is

now understimated. However, the absolute megnitudes of the CIE discrep-

ancies are lower than those observed in the cases with a harder input

spectrum.

The "NEFERTITI" programne is scheduled for conclusion in early

1983, the last configuration to be studied being 2 simulated end-of-

-cycle blanket composition.

1.3. Reactor Dynamics ---------------- Extensive comparisons have been made between the dynamics codes

SURDYN (point kinetics; developed at CEA) and NADPP (2-D kinetics,

developed at ENEA) in order to assess the influence of kinetics modelling

on the predictions of the behaviour of a 3000 MWe core in a hypothetical

LOF accident.

The results presented in / 6 / show a reasonable agreement between

the two models for the analysed case, but the energetics of the accident

as calculated by SURDYN is more benign, the power at the onset of core

disassembly being about half of that calculated by NADYP-2.

Efforts are continuing at EhTA (Casaccia) to improve accuracy and

error control capability in stepwise kinetics calculations: in this context,

new approxination methods have been pro?osed / 7 / which seem to be both

accurate and efficient for the solution of initizl-value problems, particu-

larly in cases where stiffness difficulties are present.

1.4. Cross-Sections Evaluations. Processing and Adjustments ..................................... ------- -------- In the framework of common CEA-ENEA-KFK activities on higher

Actinides, the evaluation of Cm-242 in the whole energy range has been

completed 181. As a part of the activities undertaken by ENEA (Bologna)

in support of JEF implementation, complete re-evaluations of Fission

Products Pd-105 and Pd-107 have been made, while the evaluation of Cr

is nearly completed 191.

The ENEA code chain allowing to process Eh?F/B data in CARNAVAL

format has also been completed with the implementation of the FISPET /lo/

and TOCAR 1111 modules.

As far as the CARNAVAL-IV cross-section adjustments are concerned,

works on structural materials and Actinides have been going on at ENEA

(Casaccia) in cooperation with Cadarache. An adjustment of Fe, Cr and Ni

taking into account the most recent experiments in ERMINE and RB-2 has

been made, and no furt5er activities are to be expected at short term in

this area /12/. For the Actinides, a preliminary adjustment has been

concluded, basing upon fuel pin irradiations in PHENIX; furthermore,

parametric studies have been carried out on capture cross-sections of

Am-241 (sensitivity of Pu-238, Cm-242, Am-241 and -243 buildup) and of

U-238 (in the unresolved resonance region) 1131.

2. LIGHT WATER REACTORS

The ENEL-4 Caorso BWR power station has reached 90% of its

nominal power (840 MWe) in May and will be operated at that power

until the end of the first cycle scheduled in January 1983.

Some reactor physics activities are still being carried out

at CISE (Milano) and EhTL (CRTN, Milano and DCO, Roma) relating to:

- validation of AUTOBUS, a BUR core follow-up two-dimension diffusion code, on the basis of information gathered from the operation of

Garigliano and Caorso plants;

- implementation of new modules for the PWR core design and analysis code chains. In particular, a new 3-D neutronic module (alternative

to QUA!Ti)Ry) and e simplified dynamic sirnulator for tLe evaluation

of operational transients are being set up, in view of their utilisation

for the "Unfied Design" that should be adopted for the PWRs to be installed

in Italy in the future.

3. HEAVY WATER REACTORS

Some reactor physics activities are still carried out in support

of the core design for CIRENE, a 40 m e BKWR prototype scheduled to reach

criticality in 1985.

I n particular:

- a 3-D coarse-mesh simulator(TR~?~~~) is being completed at CISE (Milano);

- experiments are being made in the critical facility RB-3 (EIEA, Bologna)

aimed at verifying the predictions of axiai and radial flux profiles and

of the reactivity worths of the liquid (H,BO ) shut-off rods. 2 3

4. B E N C W ' S

Various Italian laboratories have participated in the international

exercises generated or supported by NEACR?.

Solutions have been sent by:

- ENEA (Bologna) for the LMFBR burnup benchmark; - ENEA (Casaccia) for the LMFBR shielding benchmark; - AMn' (Genova) and CISE (Milano) for the depletion problem with adjacent

a Gd-poisoned fuel pins;

- ENEA (DIS?, Roma) for the follow-on of CSKI benchmark on spent fuel transportation cask (still in course).

Finally, two solutions are being prepared by ENEA (Bologna and Casaccia)

for the pin-cell heterogeneity problem "CADEKZA".

RSFERENCES

1 - G. Humbert et al.: "The RACINE Programme: Physics And Safety Studies in Heterogeneous Configurations", Int.1 Conference, Mannheim,

May 1982.

/2/ - F. Lyon et al.: "Verification of The Method Used for Determination of Na Void ~eactivity Distribution in A Large FBR" (in French),

SEDC/SPNR/LPR/81/50.

/3/ - C. Giacometti et al.: "Control Rod Calculation Methods And Uncertainties for A Power LMTBR Design", Int.1 Conference, Kiamesha Lake, September

/ 4 / - U. Broccoli: "The MSN Method And Its Utilisation" (in French),

/5/ - D. Antonini et al.: "Results of The First Two Measurement Campaigns of The NEFERTITI Programme", RTI/LNS(81)1, Rev. 1.

/6/ - A. Galati et al.: "Comparison Between Space Kinetics And Point Kinetics

Calculations of A LOF Accident in A Large LMFBR", Int.1 Topical

Meeting on LMTBR Safety, Lyon, July 1982.

171 - F. Norelli: "New Methods for Improving Kinetic Calculations by Minimum-Norm Polynomials",submitted for publication in NSE.

181 - E. Menapace et al.: "Evaluation of Cm-242 Neutron Cross-Sections

from 10E-5 eV to 15 MeV", TIB/FICS(82)2.

191 - E. Menapace et al.: "A Revised Evaluation of Neutron Cross-Sections

of Pd-105 and Pd-107", TIBIFICS(82)l.

/lo/ - G. Panini: "FISPET, A Code for Computing Fission Spectra from ENDFIB", RT/FI(81)21.

/11/ - G. Panini et al.: "TOCAR, An Interface Code Between FOURACES And

CARh'AvAL" (in French) , RT/FI(81) 20.

1121 - A. D'hgelo et al.: "Adjustment of Structural Materials Cross-Sections for CAIU\'AVAL-IV" (in French), 'CEA/ENEA Technical Report, in press.

1131 - G. Oliva et al.: "Resonance Parameter Data Uncertainties Effects on Integral Characteristics of Fast Reactors", SEDC/SPNR/LPR/81/6164.

JAPAN

Reactor Physics Activities in Japan

(September 1981 - August 1982) Compiled by

T. Asaoka (JAZRI) and K. Shirakata (PNC)

Thermal Reactor Physics

On the method development for dealing with the 3-dimensional transport equation, the finite element method has been applied to prism- and/or box-shaped elements and to phase s ace, by using the bilinear function of the space and angle bases.?l2) In addition, to meet the growing trend for applying the parallel computation to large-scale nuclear codes, the VENTURE has been vectorized for running on vector processors, showing the CPU time reduction of 50-70%.3)") For the ADC code, the computing time can be reduced by a factor of 3 due to the vect~rization.~)

As for the coarse-mesh method for solving the 3-dimensional diffusion equation, a computer code JAXO-3D based on the 1.5 group model has been developed for analyzing the LWR core more

a accurately than the FLARE code. In addition, a 3-dimensional core simulater TAWS has been developed to manage the BWR core more accurately and efficiently by monitoring the core characteristics with the DACS code and by predicting these with the on-line PRECS code using the power-bias factor. On the other hand, the core operation and management system COMS has been developed by integrating a 3-dimensional nuclear-thermohydraulic code for monitoring the core characteristics, a power distribution prediction code and so on. A coarse-mesh nodal coupling method has been extended to solve transient phenomena of BhXs by col- lapsing spatially into a multiregion neutronics model, an axielly one-dimension21 model or one-point model.6) Futhermore, a simple one-point core model has been developed to predict the power level and the core flow rate, for planning the start-up and the control-rod pattern exchange of BWR.') As a conventional method for the on-site reactor control, the one-group diffusion equation has been solved by using the shooting method8) for keff on the basis of analytical functions, revealing the method

a really practical for predicting the power distribution. On the other hand, a new and far simpler method for calculating the axial power distribution of a PWR core has been developed to replace the one-dimentional diffusion code calc~lation.~)

The development of a standard computer code system for nuclear calculations SRAC has been proceeded to enlarge its capability by including the cell burn-up calculations based on four FP chain models including the Ii jima model. l o ) The SRAC was used for analyzing critical experiments performed on a graphite-moderated 20% enriched uranium SEE for the Experimental HTGR, showing an agreement within 0.75% for keff. For nuclear design calculations of the Experimental HTGR, a tri-z improved coarse-mesh diffusion code HEX-3D has been developed to be used for predicting the power distribution, the control rod worth and so on.

Concerning the burn-up calculations, an LWR lattice code RESPLA has been applied to deal with the fuel with ~ d . ~ ? ) In addition, KENO-BURN has been developed for detailed burn-up calculations for the BWR fuel segment on the basis of the MGCL library.12) An analysis of a BWR core with MOX fuels of depleted uranium in an island type has been performed for showing the core characteristics compatible with the U02core. In addition, the PWR core characteristics of tight MOX lattices have been analyzed by using a multigroup transport code NULIF and a-few-group diffusion code CITATION.

As for the nuclear criticality safety, experimental techniques to determine the reactivity and the neutron inter- action effect have been developed for multi-core systems by using TCA. The variance-to-mean ratio method has been extended to apply to a two-core loading at T C A . ~ ~ )

An investigation has been made on the stability of xenon oscillation by using two-point coupled reactor model and the nodal method using the Green's function.14) In addition, an experimental technique to obtain thermal neutron spectra has been developed by measuring the peak counting rates of the capture gamma-ray spectra and by using the orthogonal function expansion method.

1) Fujimura T., Matsumura M. and Nakahara Y.: "Space and Angle Finite Element Method for Solving Three-Dimensional Multi-Group Neutron Transport Problems", NEACW-A-454(1981)

2) Fujimura T., Nakahara Y. and Matsumura M.: "Iterative Solution of the DFEM Algorithm for the Three-Dimersional Neutron Transport Problems", NEACFS-A- (1982)

3) Ishiguro M., Matsuura T. et al.: "Applicability of Vector Processing to Large-Scale Nuclear Codes", JAERI-M 82-018 (1982) (in Japanese)

4) Kamada M., Kadotani H. and Harada H.: "Vectorization of * Diffusion Code VENTURE Using CRAY-1 and FACOM 230-75 APU", JAERI-M 82-019 (1982) (in Japanese)

5) Ishiguro M. and Koshi Y.: "Vectorization for Solving the Neutron Diffusion Equation - Some Numerical Experiments", Nucl. Sci. Engng., 80, 322 (1982)

6) Motoda H., Hayase T. et al.: "Multiregion Neutronics Model Based on Coarse Mesh Nodal Coupling-Method for.Transient. Analyses of Boiling Water Reactors", Nucl. Sci. Engng., 80, 648 (1982)

7) Umegaki K., Kiguchi T. and Motoda H.: "Simple Method to Predict Power Level and Core Flow Rate of Boiling Water Reactors by Using One-Point Core Model", J. Nucl. Sci. Technol., - 19, 513 (1982)

8) Mitsui T.: "Boundary Value Problems of an Ordinary Differential Equation and the Newton Method", Mathematical Science, - 19 ( 8 ) , 41 (1981) (in Japanese)

9) Tochihara H.: "Simple Functional Method for Calculating Axial Power Distribution of PWR Core", J. Nucl. Sci. Technol., - 19 449 (1982)

10) Iijima S. and Yoshida T.: "Fission Product Model for BWR Lattice Calculation Code", J. Nucl. Sci. Technol., - 19, 96 (1982)

11) Saji E., Sakurai S. and Takeda T.: "Application of the Response Matrix to BWR Lattice Analysis", Annals Nucl. Energy, - 8, 155 (1981)

12) Naito Y., Tsuruta S. et al.: "MGCL-PROCESSOR: A Computer - Code System for Processing Multigroup Constants Library

MGCL", JAERI-M 9396 (1981)

13) Murata N., Yamane Y. and Nishina K.: "Derivation of Pal-Bell Equations for Two-Point Reactors, and Its Application to Correlation Measurenents", Annuals Nucl. Enercy, - 8, 407 (1981)

14) Kobavashi K. and Yoshikuni M.: "Analvsis of Xenon Oscilla- tion* by Coupled Reactor Model, " J. N&l. Sci. Technol. , 19, 107 (1982) -

Fusion Neutronics

At an intense D-T neutron source FNS, measurements were performed on spatial distributions of tritium production rate in a spherical Li20 assembly with a graphite reflector and on the angular de~endence of leakage spectra from Li20 slab assemblies. ' ) 21 The analyses with one- and two-dimensional transport calculations, using PALLAS-TS~) and BERMUDA-2DN based on the direct integration method in a multigroup model, have shown to represent fairly well the observed values. Also a Monte Carlo code using the double-differential cross sections (DDX), MORSE-DDX, has been applied to analyze successfully the experimental results (see Fig.1). In addition, induced activities of SUS 316 were measured in the Li20-C assembly of FNS and the results have been analyzed by using the THIDA code, showing a general agreement with the measured values except for some energy groups.

On the other hand, at OKTAVIAN, another intense D-T neutron source, measurements were performed on leakage spectra from a Pb spherical assedly to investigate the neutron multiplication characteristics and from a graphite assembly to establish the standard neutron field, the analyses being made with a one- dimensional SN transport code NITRAN using the DDX,4) in addition to the leakage spectra from natural Li, liquid nitrogen, stainless steel, concrete, water and polyethelene slabs. Angular leakage spectra from Li slabs have shown notable dis- aareements with the calculated results as shown in Fig. 2 . 5 )

- 1 ' i - n n x . . . . . . . . . . i

C O N V E N T I O N C L I ? L I i L - EX7 :E lnENi

Fig. 1 Scattered neutron spectrum by Li20 slab

Fig. 2 Leakage current spectra from natural-lithium slabs

Furthermore, the DDX were measured for D, Li, Be, C, 0, Al, Cr, Fe, Ni, Mo, Cu, Nb and Pb at OKTAVIAN by using the TOF method. )

In addition, scalar neutron spectrum measurements were performed in LiF, graphite7) and water with a developed miniature neutron spectometer of an NE213 liquid s~intillator.~)~)

The measurements were extended further to various structural materials to assess the cross sections by using the Linac-TOF method. The neturon spectra were measured in an Fe pile surrounded by a thick Pb reflector, a spherical Cu pile and a spherical Fe pile. The measurement in a spherical Mo pile has been analyzed to show that the ENDF/F-IV data give too high the flux by about 30% in the energy region above 0.5 MevlO) (see Fig.3). In addition, the reaction rate distribution in a LiF slab has been analyzed with the DOT-3.5 together with the GRTUNCL code for calculating the first collision source in a composite system, showing the need to take account of the anisotropic scattering of neutrons more accurately (see Fig.4).

A study has been made on fusion-fission hybrid reactors by developing a one-dimensional transport and burn-up code, BISON.")

Neutron e n e r g y f keV ) Fig. 3 Neutron spectrum at r=15crnan&.~O

. in. Mo-FFle: top.

Mcl,ursrl,cn,,

Fig. 4 De?th Reaction-rates distributions:on:khe central axis of the LiF slab.

1) Nakamura T., Maekawa H. et al.: "Integral Experiments on Lithium Oxide Spherical Assembly with Graphite Reflector and on Duct Streaming", 3rd IAEA Technical Committee Meeting (1981)

2) Nakamura T. and Maekawa 8.: "Blanket and Shield Experiments in Fusion Neutronics Source (FNS)", IAEA-CN-41/0-4, 9th Int. Conf. Plasma Physics and Controlled Nuclear Fusion Research (1982)

3) Suzuki T., Ishiguro Y. and Matsui Y.: "PALLAS-TS: A One-Di- mensional Neutron Transport Code for Analyzing Fusion Blanket Neutronics", JAERI-M 9492 (1981) (in Japanese)

4) Yamamoto J., Takahashi A. et al.: "Neutron Transport Calcu- lations by Using Double-Differential Cross Sections", J. Nucl. Sci. Technol., - 19, 276 (1982)

5) Takahashi A., Yamamoto J. et al.: "Measurements of Neutron - Multiplication by Lead Shells and Leakage Spectra from

Lithium, Graphite and Stainless Steel Slabs", 12th Symp. Fusion Technology (1982)

6) Takahashi A., Yamamoto J. et al.: "Measurement of Double Differential Neutron Emission Cross Sections with 14 MeV Source for D, Li, Be, C, 0, Al, Ni, Mo, Cu, Nb and Pb", Conf. Nuclear Data for Sci. and Technol. (1982)

7) Yamamuro N., Sekimoto H. et al.: "An Experiment of Scalar Neutron Spectrum Measurement for Evaluation of Tritium Production in Fusion Blanket", Bull. Research Lab. Nucl. Reactors, 6 , 1 (1981)

8) Sekimoto H., Ohtsuka M. and Yamamuro N. : "A Miniature Fast-Neutron Spectometer for Scalar Spectrum Measurement", Nucl. Instr. Meth., - 189, 469 (1981)

9) Sekimoto H., Ohtsuka M. and Yamamuro N.: "The Perturbation Produced in the Neutron Spectrum of an Assembly by a Spectrometer", Nucl. Sci. Engng., 80, 407 (1982)

10) Mori T., Nishihara H. et al.: "Measurement and Analysis of Neutron Spectrum in a Molybdenum Pile", J. Nucl. Sci. Technol., 2, 427 (1982)

11) Oka Y., Furuta K. and An S.: "Concept and Nuclear Per- formance of Power-Producing Fast Fission Blankets for Fusion-Fission Hybrid Reactors Using Equilibrium Fissile Fuel", J. Nucl. Sci. Technol., - 19, 166 (1982)

Shielding

Concerning the 3-dimensional transport method, a discrete ordinates code ENSEYBLE in (x,y,z) geometry1) has been extended to deal with (r,e,z) geometry, using the variable weight diamond difference equation and a discrete nodal transport meth~d.~) In addition, a numerical method for (x,y,z) geometry has been developed on the basis of a direct integration method of the integral transport equation3 ) ) and it has been applied to determine accurately the neutron fluence in the pressure vessel of PWR.5) ' Furthermore, the Monte Carlo method has been applied to deal with a radwaste facility by using the source energy bias, the source location bias and the path length bias.

As for streaming problems, the Monte Carlo coupling technique has been applied to analyzing 3-dimensional neutron problems: two-legged cylindrical-annular duct problem and streaming problem through a slit.6) In addition, an albedo formulation incorporated into a Monte Carlo code has been applied to gamma-ray streaming problems of one- and two-bent ducts and neutron streaming problem of one-bent ducts.') An experiment on neutron streaming through a rectangular air duct was performed on JRR-4 to be used for checking the accuracy of 2- and 3-dimensional transport codes.8) Furthermore, spectral and spatial distributions of neutrons and garma rays were measured in a simple cavity-duct configuration to observe profiles of cavity streaming. An examination on the applicability of the albedo Monte Carlo method to this cavity-duct system has shown the necessity to improve especially the albedo dataas) An incorporation of an albedo formulation to DOT-3.5 was performed to result in DOT-ALS, which has been shown a powerful capability to treat neutron skyshine problems as well as streaming problems.

In connection with a tokamak fusion reactor, INTOR-J, the effect of radiation streaming through the neutral beam in- jection port and divertor throat was evaluated using the Monte Carlo and lo-6 l l ~ o t ~ g .

discrete ordinates method.lO) In ad- L - --' dition, by using FNS, an intense I<'

neutron source based on D-T reaction, - - a duct streaming experiment was carried 'i"" out by utilizing an L-shaped personnel access way in thick concrete wall of the target room. The analysis with the MORSE-GG has reproduced fairly w e 1 the measured result, as shown in Fig.5, except at the outermost point where the - statistics are quite poor.ll)

Concerning penetration problems, I

neutron reaction rates were measured through thick Na shields by using YAYOI, showing an agreement of the = I I

analysis with DOT-3.5 within 25%.12) ~ ~ " , ; 1 : ' A l! I;. ;' . --a- 9-"1

In addition, measurements were per- ., ~ i ~ . 5 Fast neutron formed on hydrogenous materials by spectrum in the

duct

and

1)

using a neutron beam due to a Cf-252 source. For gamma rays, an experiment was carried out on Pb and Fe for N-16 gamma rays from the primary coolant of JRR-4. Furthermore, a unified build-up factor formula has been developed for one- and two-layers of shielding materials.

A study has been made on the penetration of secondary neutrons and gamma rays through graphite, iron, water and ordinary concrete assemblies, which are generated from 52 MeV proton bombardment of a graphite target. Analyses by using the Monte Carlo code and ANISN code have shown, on the whole, a good agreement with the measurements. 3, In addition, an optimization study has been performed on the shield composition of a D-T fusion reactor to minimize the shut-down dose rate outside the shield. l 4 )

As for the shielding of spent fuel transport casks, measurements were performed on the dose rate outside a TN-12A cask for PWR fuel assemblies, the result being lower by about 10% than the calculated value from ORIGEN, QAD, ANISN and DOT-3.5, and on gamma-ray spectrum to identify the source nuclides. Furthermore, the dose rate distribution was measured around two HZ-75 casks and one NH-25 cask for BWR fuel assemblies in the cask transport ship. A preliminary analysis on shielding experiments to confirm the reliability of a shielding safety evaluation code system has been performed on ORIGIN-JR for source evaluations, ANIBURN for cell constant calculations, KENO-IV for neutron multiplication evaluations, and AIVISN-JR

DOT-3.5 for radiation transport calculation^.^^)

Yokobori H., Nishimura T., and Tada K.: "Application of a Three-Dimensional Discrete Ordinates Transport Code to Shielding Design and Analysis", NEACRP-L-250 (1981)

Nishimura T., Tada K. and Yokobori H.: "Development of Discrete Ordinates Transport Code in Three-Dimensional (R,e,Z) Geometry for Shielding Design", J. Nucl. Sci. Technol., - 19, 80 (1982)

Takeuchi K. and Sasamoto N.: "Fundamental Theory of the Direct Integration Method for Solving the Steady-State Integral Transport Equation for Radiation Shielding Calculations", Nucl. Sci. Engng., 80, 536 (1982) Sasamoto N. and Takeuchi K.: "Direct Integration Method for Solving the Neutron Transport Equation in Three- Dimensional Geometry", Nucl. Sci. Engng., 80, 554 (1982) Takeuchi K. and Sasamoto N.: "Three-Dimensional Discrete- Ordinates Calculation for Accurate Determination of Neutron Fluence in Reactor Pressure Vessel", 4th ASTM- EURATOM Sym. on Radiation Dosimetry (1982)

Ueki K.: "Three-Dimensional Neutron Streaming Calculations Using the Monte Carlo Coupling Technique", Nucl. Sci. Engng., 79, 253 (1981)

Itoh Y., Nishihara Y. and Kinno M.: "Gamma Ray and Neutron Streaming through Bent Ducts", J. Atomic Energy Soc. Japan, - 24, 550 (1982) (in Japanese)

Yamaji A. and Miura T.: "Experiment and Analysis Based on a Simplified Method of Neutror, Streaming through a Rectangular Air Duct", Research Report of Ship Res. Inst., 19(2) (1982)

Shin K., Murakami R. et al.: "Measurements of Neutron and Gamma-Ray Streaming in a Cavity-Duct System and an Analysis by an Albedo Monte Carlo Method", Nucl. Sci. Engng., 81, 161 (1982) Seki Y., Iida H. et al.: "Radiation Streaming Calculations for INTOR-J", Nucl. Technology/Fusion, - 2, 272 (1982) Nakamura T. and Maekawa H.: "Blanket and Shield Experiments in Fusion Neutronics Source (FNS)", IAEA-CN-41/0-4, 9th Int. Conf. Plasma Physics and Controlled Nuclear Fusion Research (1982)

Oka Y., An S. and Hashikura H.: "Neutron Penetration through Thick Sodium", Nucl. Sci. Engng., 79, 308 (1981) Uwamino Y., Nakamura T. and Shin K.: "Penetration through Shieldinc Materials of Secondarv Neutrons and Photons ., Generated by 52-MeV Protons", Nucl. Sci. Engng., 80, 360 (1982)

Seki Y. and Iida H.: "Fusion Reactor Shield Optimization in Terms of Personnel Access", J. Nucl. Sci. Technol., 19, 11 (1982) - Katakura J., Komuro Y. et al.: "Preliminary Analysis on Shielding Experiment of a Spent Fuel Transport Cask", JAERI-M 9957 (1982) (in Japanese)

Fast Reactor Physics

I. Design Studies for Large LMFBR Cores

Core optimization studies have been performed for large LMFBR cores, focussing on high breeding and safety performance. Core performance characteristics have been studied for homogeneous core and radially or axially heterogeneous equivalent core, and results were compared. Major findings or general trends obtained through these studies are summaried as follows:

While the doubling time of a homogeneous core depends very much on the fuel pin size, the doubling time of a radially heterogeneous core is relatively independent on the fuel pin size.

The inventory doubling time is not sensitive to the imposed maximum linear heat rate., and is greatly improved by increasing the effective fuel volume fraction.

The optimum quantity of internal blanket assemblies of a radially heterogeneous core is about one fourth of the total assemblies, determined by minimizing the inventory doubling time.

Both the fissile inventory and the inventory doubling time are not very much different respectively between homogeneous and radially heterogeneous equivalent cores.

The sodium void reactivity worth in the driver fuel region of a radially heterogeneous core is about 40% lower than that of a homogeneous core.

The absolute value of fuel Doppler reactivity worth of a radially heterogeneous core is about 40% lower than that of a homogeneous core, due to the higher fuel enrichment in the heterogeneous core.

In case of a radially heterogeneous core, power distribution change due to fuel burn-up and control rod insertion is usually larger than in a homogeneous core. In case of an axially heterogeneous core, however, it is nearly the same as in a homogeneous core.

Safety Analysis of Large Heterogeneous LMF'BRs~)

The potential safety advantage of large heterogeneous LMFBRs in hypothetical core disruptive accidents has been studied in contrast with that of the conventional homogeneous LMF'BRs. The main objective of this study is to investigate the inherent safety features during accident sequeces through comparison between the two types of cores. Neutroni- cally optimized 1000 MWe heterogeneous and homogeneous cores (Fig.1) have been designed on the same technological basis. The heterogeneous core designed here is characterized by the adoption of 6 mrn pellet diameter, 80 cm core height and

island-type configuration resulting in a very low sodium void reactivity. Safety analyses for loss-of-flow and transient over-power accidents were made using the SAS3D and VENUS codes. As a result of this study, it was found that the heterogeneous core studied here has smaller possibility of reaching prompt critical and that even if it should reach prompt critical by the adoption of very conservative assumptions, the resulting work energy may be about a half that of the homogeneous core. It is concluded that the heterogeneous core with a lower void reactivity has a significant advantage for accommodating the energetics issues over the homogeneous core, when rather conservative assumptions are employed for the analysis.

The SAS3D code is transmitted from USDOE and ANL/RAS to PNC under Special Memorandm of Agreement on LMFBR Safety.

f u d ass-ly 378 i 3 1 5 7 : iC 207

b l a c assembly 445 (= 2S8 fue l aaserjly 4i3 (OC 186

p r - 5 a q rod 24 bljPier asse=jly 252 secondary rod 11 pr-r? m d 24

. -. srcan- n d 6

Fig. I .Layouts of Heterogeneous and Homogeneous Cores

3. Extrapolation Errors of Design Parameters of Large LMIE'BRs*)

An evaluation of prediction accuracy was performed for the neutronics parameters of large LMFBRs. With this end in view, the origins of the prediction uncertainty were categorized and the uncertainty was estimated for each category to grasp the total uncertainty as a statistical sum of each item.

Among the origins of the uncertainties, the extrapolation error caused by nuclear data uncertainty was studied in detail by extending a method proposed in the previous phase of the present series of study. Other origins of the prediction uncertainty were examined by a full use of the information

b obtained in the JUPITER experiments and their analyses. The prediction accuracy was evaluated as follows.

Effective multiplication factor 1.2 % . Control rod reactivity worth 8 %

Power distribution : in core 3 % in blanket 4 %

A large portion of the ke;f error (1.2 % ) comes from a mismatch in the Pu isotopic rados between the mockup and the design target. This error will be reduced down to 0.6 % provided that the reactivity effect of higher Pu isotopes (especially 2 4 1 ~ ~ ) is predicted in an accurate way.

4. Evaluation of Neutron Nuclear Data for 241Am and 243~in3)

Neutron nuclear data of 2 4 1 ~ m and 243Am were evaluated for JENDL-2. Evaluated quantities are the total, elastic and inelastic scattering, fission, capture, (n,2n), (n,3n) and (n,4n) reaction cross sections, the resolved and unresolved resonance parameters, the angular or energy distribution of the emitted neutrons, and the average number of neutrons emitted per fission. The fission cross section was evaluated on the basis of newly measured data, .and lower values than JENDL-1 were given in the subthreshold energy region. The reliability of the calculation parameters are also much improved, because experimental data became available for the total and capture cross sections of 241Am in the high energy region.

. 5. Benchmark Tests of JENDL-z4) r 5 )

Benchmark tests have been made on JENDL-2 for fast reactor application.

(1) Benchmark calculations using JENDL-2B-70

JENDL-2B-70 is a 70 group cross-section set generated from preliminarily provided JENDL-2B. Using this cross-section set, various characteristics in core centre have been calculated for total of 27 assemblies.

Satisfactory results have been obtained as a whole. The positive sodium void reactivity worth is significantly

overestimated. The sensitivity analysis with the generalized perturbation method suggests that this overestimation could be dominantly caused by the underestimate of P-239 fission cross- section below the sodium resonance.

(2) Benchmark tests using JFS-3-32

JFS-3-J2 is generated from JENDL-2B and was provided by weighting a collision density spectrm for core composition of a typical fast reactor. This can avoid the overestimate of elastic removal cross-sections caused by using 1/E-neutron spectrum as adopted in JENDL-2B-70.

Similar benchmark calculations have been made using . JFS-3-J2. The differences between the two cross-section sets give no significant effects on most of physics quantities. However, Doppler worth obtained by JFS-3-32 is 10 - 17% lower than that by JENDL-2B-70. And JFS-3-Z2 also improves the agreement between calculation and measurement of sample worth. a 6. Development of Homogenization Method for Heterogeneous

Control Rod channel )

A homogenization method have been developed for a heterogeneous control rod channel. Effective cross sections which preserve the integrated reaction rates in each energy group are obtained by using a super-cell composed of a control rod channel and a surrounding fuel region. The method has been applied to the calculation of the pin rod worths in ZPPR-1OA assembly, and the applicability has been checked.

7. Analysis of JUPITER ~x~eriments~)

The ZPPR-9, 10 experiments were analyzed with JENDL-2B, and the following results were obtained for physics parameters.

(1) Keff values were underpredicted by about 0.8%.

(2) Radial dependences were observed in reaction rate C/E distributions, which had peak values near the inner core-outer core boundary. 238~(n,f) was overpredicted by more than 10% at the innermost blanket region.

(3) Material reactivity worths of heavy nuclides were overpredicted by 5 to 13%, and worths of nuclides of structural materials were overpredicted by about 20%. U02 Doppler reactivity worths were underpredicted by about 12%.

(4) Sodium.void reactivities were overpredicted by about 30%.

(5) The average C/E value for control rod worths was 1.02+0.04.

The DOE/PNC Joint Physics Large Heterogeneous Core Critical Experiments Program, called JUPITER Phase I1 Program, would involve 1 year and 8 months of measurements. The experiments started as ZPPR-13 program on May, 1982, using the ZPPR facility of Argonne National Laboratory.

8. Mock-up Experiments for JOYO MK-I1 Core at FCA

Mock-up experiments have been done at FCA to support the JOYO MK-11 Program. The main purposes are to verify the reliability of the supervisory core performance code and to support the irradiation and refueling plans of MK-I1 cores. Experiments were started on March, 1982 and are done in the FCA X assembly series, i.e., FCA X-1, X-2 and X-3. FCA X-1 is a clean benchmark with radial blanket, and X-2 and X-3 are physics and engineering mock-ups with radial reflector. Reaction rate distributions and other physics parameters will be measured in detail in the mock-up systems with reflectors.

9. Actinide Integral Experiments at FCA

A series of actinide integral experiments have been made on FCA IX assemblies for evaluating cross-section data of Np-237, Pu-238, Pu-240, Am-241, Am-243 and Cm-244. These actinide nuclides are important from the actinide transmu- tation view point. The FCA IX consists of seven different version of cores to cover a wide range of neutron spectra. The sample worth was measured at the centre of the cores by the criticality method with the accuracy of less than 25 x Ak/k. The preliminary analysis indicated that there was relatively large discrepancy between the measured and calculated worths of almost all the samples except Np-237. Detailed analysis is under way. The measurements of fission rate ratio of actinides to U-235 have been made at the centre of the cores by the fission chamber technique. The measured fission rate ratios are compared with the calculated ones by ENDF/B-V and transport theory with S,P1 approximation. The results show that the calculations overestimate the measurements by 4 - 17% in most cases. However, the calculation for Pu-238 underestimates the measured one by about 25%.

10. Research on Shielding

(1) Analyses of JOYO Shielding Measurements

In 1979, shielding characteristics of JOYO (Fig.2) were evaluated by the two-dimensional discrete ordinate method (Program DOT-3.5), and the calculated results were compared . with the shielding measurements at JOYO. The supplementary analyses have been performed this year.

Flux distributions near the control rods and the effects of the detector guide tube on the measured data in the graphite and in the concrete regions have been analyzed: C/E values of these data were not good in the previous two- dimensional Sn analyses.

Newly measured data such as the flux distributions through the main coolant pipe penetration, flux distributions in the IHX room, and the activation level of the sodium coolant were analyzed by the two-dimensional Sn and albedo

Monte Carlo codes. Neutron flux distributions in the complex geometry were also analyzed by the three-dimensional Sn code.

(2) Preparations of Group Cross-Section Sets from JENDL File

For analyses and design calculations of FBR shielding, we have mainly used the cross-section sets which were prepared from ENDF/B-IV file by the RhDilEAT system of JAERI; We are going to revise these multi-group cross-section sets by using JENDL file. SUPERTOG code in RADHEAT system was checked for JENDL file and infinite dilution cross sections of several elements were calculated. Checking the data by the benchmark problems (such as NEA shielding benchmark), we will revise all cross-sections and self-shielding factors for FBR shielding calculations.

(3) Development of Albedo-Sn Transport Code DOT-ALB

The albedo-Sn transport code DOT-ALB has been developed from the DOT-3.5 code. The code can take the albedo boundary condition with energy-angle dependent differential albedo at the upper, the lower and the right boundaries. On the albedo Sn option, the asymmetric angular quadrature sets are adoptable.

The neutron skyshine experiments conducted at the reactor facility YAYOI, University of Tokyo was analyzed with P3-548 approximation as a benchmark test of the code. The DOT-ALB code described well the neutron spectra and the dose rates at the distance up to 1 Km from the source within a factor of 0.5 - 1.9. It was confirmed that the albedo scattering at the ground sffecced strongly the neutron spectrum obtained near the ground.

For the application, a problem was chosen on neutron streaming through a sodium pipe chase-way surrounded by a concrete shield of a typical prototype FBR. The albedo-Sn calculation using the boots-strap technique without any overlapping area turned out to save computer time by 56% compared with that of the reference calculation for whole geometry. The results of the former agreed with those of the latter.

1) Suzuki, K. et al.: "A Study on the Potential Safety Advantage of Large Heterogeneous LMFBRs", Int. Topical Meeting of LMFBR Safety and Related Design and Operational Aspects, Lyon, France, (1982)

2) Kamei, T. et al. : NAIG Annual Review 1981, 8 (1981)

3) Kikuchi, Y.: JAERI-M 82-096, (1982)

4) Kikuchi, Y. et al. : J. Nucl. Sci. Technol., - 17, 567 (1980)

5) Kikuchi, Y. et al. : "Present Status and Benchmark Tests of JENDL-2", Int. Conf. on Nuclear Data for Science and Technology, Antwerp, Belgium, (1982)

6 ) Takeda T. et al. : NEACRP-A- (1982)

7) Shirakata, K. et al.: JAERI-M 9999, 161 (1982), (in Japanese)

. . .

Fig. 2 Main Shield of "JOYO"

National Programs

1. JOY0

At the Experimental Fast Reactor "JOYO", normal operation at 75 MWt was started in January, 1980, and was continued until December, 198: in order to accumulate technical data of the present core. Concerning the performance characteristics of the reactor, the experimental results so far obtained by various tests have been in general satisfactory, being in good agreement with the predicted values.

A series of natural circulation tests were performed at. the end of December, 1981. These tests were carried out stepwise from low power ( Q 1 MWt) to full power (75 MWt) with detailed plant dynamics analysis. Experimental results showed that the cooling system has the ability to remove decay heat by only the natural circulation.

The MK-I1 program was started in January, 1982. The core has ever since been converted to a core of 100 MWt power by replacing the MK-I fuels with MK-I1 fuels. Approximately 300 MK-I assemblies will be replaced with MK-I1 assemblies. Achievement of the criticality with new core is expected in late fall 1982 and the power ascension testing to 100 MWt will be completed in the spring of 1983. The reactor will be utilized as an irradiation facility for fuel and material development programs.

2. MON JU

Application for licensing for the construction of the Prototype Fast Breeder Reactor "MONJU" was filed to the re- gulatory body on December 10, 1980. Since then, the safety analysis reports had been evaluated by the Science and Technology Agency of the Japanese government until December of 1981. In the next place, the safety evaluation by the Nuclear Safety Commission of Japan was started in May, 1982.

The land preparation of the site needs appr~v~alof the governor, and the application for approval has been filed to Fukui prefecture. On the other hand, negotiation for the contract of the plant is under progress between PNC and manufacturers.

Principal design and performance data of MONJU are shown in Table 1. The reactor system and the core configuration of MONJU are shown in Figures 1 and 2.

3. Demonstration FBR

One demonstration plant will be constructed on the way from JOYO and MONJU to commercial fast breeder reactor plants. Design studies of the demonstration plant which is 1,000 MWe loop type plant aiming its commencing of construction in the beginning of 1990s, have been and are being conducted in these years.

Japan is now in just transition stage from a studing period to a focussing period in which two matters will be required, tlat is (1) preparation of a unified specification for the fundamental design, and (2) starting up of the research and development activities for the demonstration plant.

The primary conceptual design directing the extrapolation of MONJU, was performed from 1979 to 1981. It will be utilized as a candidate design of the demonstration FBR plant.

The secondary conceptual design aiming mainly at reduction of construction cost has been started in 1982. National economical condition requires the construction cost be less than the twice of LWR from the view point of future commerciali- zation of FBR. Some design features to be investigated in the study are as follows;

(1) introduction of bellows joint for main heat-transport-system piping

(2) reduction of the number of control rods and rows of radial blanket assembly

(3) elimination of handling of the outer row of shielding assembly by fuel handling machine

(4) reduction of the diameter of reactor biological-shielding- concrete relating to above improvement

( 5 ) size reduction in whole system and components of the plant

(6) making simpler and smaller fuel handling system

(7) making the plant system parameter survey for optimization

(8) reviewing the design criteria, codes, standards relating to cost reduction.

The avove descriptions are based on the design study sponsored by PNC. Also the utility group is conducting design study of

e a demonstration plant separately.

Both streams are just on the point of flowing into a design unification effort. The effort will be one of key activities for early realization of the demonstration plant in Japan.

4 . FUGEN

"FUGEN" is the 165 MWe Pu-MOX fuelled prototype reactor, started up in 1978, which is heavy water moderated, boiling light water cooled, and of pressure tube type.

During the scheduled shutdown in November 1980, stress corrosion cracking (SCC) was found in. stainless steel pipgs of the residual heat removal system and emergency core cooling system. All the defect pipes which were type 304 stainless steel were replaced by type 316 (low carbon) stainless steel one, the material of which has excellent resistance against the SCC.

After the repair, the second annual inspection and the third refuelling, FUGEN came back to generate electricity in October 1981 on schedule. At the third refuelling, 20 assemblies of the higher enriched Type B fuels (1.3% Pu-fissile + NU, or 1.9% EUo2) were charged instead of 'thoseof the'initial Type A fuels (0.66% Pu-fissile + NU, or 1.5% EU02). In June 1982, the fourth refuelling was carried out and.-FUGEN has- continued stable full power operation. The load factor from July 1981 to June 1982 was 58%.

The 92 MOX and 92 U02 assemblies, including four special fuel assemblies, have been discharged up to the fourth refuelling. The maximum burn-up of MOX fuel is 12,40OMWd/t, and no leaking fuel has been found for more than 717 effective full power days of operation up to the end of May 1982. The discharged fuel assemblies were inspected visually and dimensionally, using the spent fuel inspection instrument installed in the spent fuel storage pool. A small amount of crud deposition was observed on the fuel rods, but the other external appearances remain unchanged. A result of dimensional inspection reveals no abnormal deformation of fuel rods.

Extensive studies have been made on reactor physics during these burnup cycles, particularly related to the core management problems. Power distribution control and refuelling management have been done very successfully, and the estimated mean-square root errors on the 3-D power distributions were within 13%.

5. Demonstration FUGEN-HWR

As for the 600 Fugen-HWR demonstration plant, the construction program is now fixed with the decision given by Japan AEC. Hence, PNC is actively cooperating with EPDC (Electric Power Development Company), the contractor of the plant, for all sorts of preparatory works necessary for starting its construction. It is roughly expected now that the commencing of construction will be in 1988 and that the initial criticality will be attained in 1994.

For the purpose of investigating the nuclear characteristics of commercial-scale FUGEN type reactor and to give support to successful operation of the prototype reactor FUGEN, studies of reactor physics parameters have been continued by using uranium and plutonium fuels in DCA (Deuterium Critical Assembly).

Recent measurements have been made to obtain useful informations for nuclear design of the commercial-scale reactor, on 25.0cm pitch square lattices loaded with several kinds of Pu02-U02 clusters which have 36 fuel pins of 16.5mm diameter. They were 0.87~10 enriched Pu02-U02 clusters, 0.87w/o enriched Pu02-U02 clusters included Gd203-U02 fuel pins, and 0.87w/o enriched Pu02-U02 clusters whlch included I . ~ W / ~ U02 fuel pins.

The measured items are : (1) microscopic and macroscopic

power distributions in the core, ( 2 ) decrease effect of power peaking with burnable poison, (Gd203), ( 3 ) loss of coolant void reactivities, and ( 4 ) microscopic gamma-ray deposition distributions in the core configurations.

In order to evaluate coolant void reactivities in the core in which BI;C coctrol.rods were arranged, collant void reactivity changes have been measured in the core consisted of 0.54W/o enriched Pu02-U02 clusters surrounded by 1.2~/oU02 clusters.

Conrol Rod Drive \ Rotating P!ug ?rive

uel Handling Faciiitiesi

Reac+ar Vessel

Sodium Storage' Tank

1

Fig. 1 "MON3UW Reactor System

core f u e l - S/A - ---l-iZl~%~ ::

C'" ." Core Configuration

a d i a l b l a n k e t f u e l S / A

c o n t r o l . r o d

n e u t r o n s o u r c e

n e u t r o n s h i . e l d i n g

s u r v e i l l a n c e S/A

@ 1 1 7 2

. @

@ ---

0 @) .

1 9

2

31 6

0

Table 1 P r i n c i p a l Design and Performance Data o f MONJU

Reactor Type Sodium cooling loop type

Thermal Power 714 MW

Electrica! Power about 280 M W

Fuel Material PuO2 - UO2

Core Fuel Equivalent diameter 1,790 mm

Height 930 mm

Volume

Pu Enrichment (Pu fissile %)

Initial core

Equiiibrium core

Fuei Inventory Core (U+Pu metal)

Blanket (U metal)

Average Burn up

Cladding Material

Ciadding Outside Diameter 1 Thickness

Permissible Cladding Temperature (middle of thickness)

Power Density

Blanket Thicknes (axialIradial)

Ereeding Ratio

Reactor inlout Sodium Temperature

Secondary Sodium Temperature (IHX outlet / IHX inler)

Reactor Vessel (hightldiameter)

Number of Loops

Pump Position (primary and secondary loop)

Type of S;eam Generator

Steam Pressure (turbine inlet)

Steam Temperature (turbine inlet)

Refueling System

2,335 lit.

Inner core / Outer core

15 1 2 0

16 1 2 1

5.9 Ton

17.5 Ton

80,000 MWDD

SUS316

6.5 10.47 mm

675 OC

Upper 300 mm

1.2

Cold leg

Helical coil, once-through unit type

Single rotating plug with fixed arm FHM

Refueling Interval 6 months . .

J u l y I981 - J u l v '982

Compiled by N. Sustraan

I. Reactor Physics et the Snergv Research Centre, Petten *

1.1. Support to fast breeder reactor development

Eission-uroduct data

The status of recent fast capture cross section evaluations for important

fission-product nuclides has recently been reviewed / 1 1 . One of the conclusions is that pseudo fission-product cross sections as calculated from

four different files (i.e. CNENICEA, JENDL-I, ENDFIB-V and RCN-2A) agree

within 1 % when the average capture rate in a fast power reactor is cal-

culated. As a contribution to the recent discussion on the "NEACRP LMFBR

benchmark calculation intercomparison for fuel burn-up" we give here our

calculated pseudo fission-product capture cross sections in the SPXl

type central spectrum (Table VII of the proceedings):

RCN-2A + ENDFIB-IT: ac=0.508 blfission

ENDFIB-V : ac =0.505 blfission

These data apply to fission products from 239?~; the yields used in the

burn-up calculation (41 MWdIkg) are the same as those adopted in ENDFIB-V.

All gaseous and volatile fission products have been included. Assuming that

the stable and long-lived isotopesof Br, Rr, I and Xe have disappeared, we

find a reduction of 5%. This reduction increases to about 12% in the limit of

immediate release of all gaseous and volatile nuclides and their decay products

(e-g. 133cs, 135c4. Activation of the Na-coolant

A project to evaluate activation cross sections of corrosion products,

cover-gas nuclides and other nuclides in the primary cooling circuit of

a fast power reactor has recently been completed. A report on the evalua-

tions for Z2Na (produced from the 23~a(n,2n) reaction), 36~r, 38~r, 40~r

(cover-gas) , 50~r, j4Fe, 58g~o, 58m~o, 58~i, 62!Ii, 64Ni (corrosion products) and 64~n, 1 1 2 ~ n (contaminants) will be presented at the forth-

coming Antwerp conference 1 2 / .

I 1 1 H. Gruppelaar, Status of recent fast capture cross section evaluations for important fission product nuclides, XEAXDC/NEACRP Specialists' Meeting on Fast -Neutron Capture Cross Sections, Argonne, 20-23 April, 1982 (ECN-82-045).

121 H. Gruppelaar and H.A.J. van der Kamp, Svaluation of activation cross sections of corrosion products, cover-gas nuclides and other nuclides in the primary cooling circuit of a fast power reactor, to be presented at the Int. Conf. on Nuclear Data for Science and Technology, Antwerp, 6-10 Sept. 1982.

* DeBeNe cooperation on fast breeder reactor development. 9 1 r3 2 0 !"*

1.2. Neutronics for Fusion Reactors

, The two dimensional neutron transport calculations for the JET neutron

diagnostics performed with the FURNACE code system for the two full

aperture plasma scenario's (for DD and DT burn) have been completed.

The results will be presented at the 12th SOFT I I 1 . The cooperative effort at Ispra, JGlich and Petten on activation, trans-

mutation and afterheat has been concluded, and the results published \ 2 / . As a contribution to the European Blanket Technology Study Group calcu-

lations have been performed on the release of activated materials from

the first-wall of IhTOR, due to the erosion.

. A contribution on the neutronics properties of ternary alloys (LiPbX)

and alternative neutron multipliers is in progress, supported by cross-

section evaluation for nissing group cross section data.

The study on the sensitivity of blanket parameters to precompound effects

in double-differential cross section data / 3 / is in progress.

1 1 1 K.A. Verschuur, Neutron Transport Calculations for JET Neutron Diagnostics. 12th SOFT, Julich, Sept. 1982.

121 R.J. Verbeek et al. Neutronics Performances of Candidate First- Wall Materials. EUR-FU-BRU-XII-102182-NEUTR, March, 1982.

131 H. Gruppelaar, C. Costa, D. Nierop and J.M. Akkermans, Calculation and ~rocessine. of continuum article-emission sDectra and angular - - distributions, to be presented on the Conf. on Nuclear Data for Science and Technology, Antwerp, Sept. 6-10, 1982.

1.3. Experiences with the on-line power noise monitoring system for the

Borssele (PWR) power reactor.

After an extensive experimental program 1 1 I in which the reactor noise was studied during eight fuel cycles of the Borssele reactor, an on-line

real-time reactor noise monitoring system has been developed and in-

stalled. By this system it is possible now to continuously follow reactor

operations at the Petten site which is connected to the Borssele reactor

by a 200 km long telephone line.

This system came into operation after September 1981. Since then reactor

shut-down of the 8th fuel cycle, testing of the primary coolant system

pressure signals at low temperature and the reactor start-up of .the 9th

fuel cycle upto full power operation in February 1982 and the power

operation since then have all been followed on-line at Petten. The re-

actor safety channels, in-core neutron detectors, core-exit thermocouple

signals and tne signals of the secondary syster, (e.~. pressure and flow

in the steam line and generated electric power) are continuously moni-

tored and reported. ?ram time to time axial anc radisi vibrations of

the two primary coolant ?imps are checked.

Integrity of the reactor saiety channels is monitorei from the white

noise contribution of :he ior.-chanbers and the long term changes in

physical parameters of the reactor system (due to changes in boron con-

centration) have been followed. Core physics parameters (reactivity pres-

sure coefficient), transfer function of the reactor system are monitored

from combining pressure- to neutronic-noise. In-core, ex-core and exit

thermocouple temperature noise provides the infomation on the flow

condition of the reactor. F r m the ex-core xeutron detector signals

core-barrel motion uplitudes and direction of the motions are con- @ tinuously followed. - i3 concluslon,the on-line mnitoring sys:ez is ?rovid<ng 2 continuous

source of highly valuable infomation on tie stare of reactor operations.

j 1 1 E. ~Grkcan, Review of 3orssele 3!43 Yoise Exgeriaents Ai?,lalysis 2nd - instrumentation. "?rog. Sucl. Sr-ergy 2 (i982) 437.

Tae 3hYSIG81 libran .................... ,F .he daisage cross-secfion library 3AMSIG81 I / is an updared and extended

version of the damage cross-section library (Dh?fSIG77).

The library contains energy dependent groug cross-section data for a

number of materials to facilitate t h e calcu?ations of damage production

(based on displacements of atoms), the calculation of probably zones and

the calculation of gas production sue to (n,a) and (n,p) reactions. The group cross-section data are given for a fine group structure of the

SAND-I1 type with 640 groups.

This library contains for some materials aore than one cross-section set . . - - originating from acrerent evaluations.

54, Cross-section data sets for the activation ~esctions re(n,p), j8?Ji(n,?)

and 63~u(n,a), which reactions are commonly csed to 6etemine themal

and fast neutron iluences, have been included also.

Xoreover also some artificial cross-sections are incor?orated in chis

librtry, whicn can be .used to czlculate values for some ?hysical quan- . . . .

cities charzcter~zizg neutron spectra, snch ss Dean lethargy <a>, 3ean

energy <E>.

Also cross-sections for 5, Al, and Cd are included; these are required

to reach compatibility with other libraries in the SANQ-I1 format.

The DOSCROSBI libraz ------------------- The cross-section library DOSCROS81 121 is an updated and extended ver-

sion of the dosimetry cross-section library DOSCROSS77.

The library contains energy dependent fine group cross-section values

for a number of reactions which are applied in neutron metrology and in

neutron activation spectrometry.

The library contains data from the ENDFIB-V file supplemented with in-

.formation from the ENDF/B-IV and from the INDL/V.

-The total number of reaction cross-section sets incorporated in this

library is 70 (+3 cover cross-section sets).

The library will be available in a computer compatible form from the

OECD NEA Data Bank and from the RSIC at Oak Ridge and numerical data

are available on microfiche upon request to ECN.

REAL-80 ~roject -------- -- -- The aim of the REAL-80 exercise, organized by the IAEA, was to arrive

at a r&listic value for the total uncertainty in integral radiation

damage parameters (like the displacement rate) when such a value is

derived by means of existing unfolding procedures. The spectrum data

referred to the thermal reactor ORR and the fast reactor YAYOI. The

responses (62 solutions from 12 laboratories) were analysed by ECN Petten,

in close collaboration with the Budapest Technical University.

A first draft for the final report on this exercise is now available 131.

1 1 1 W.L. Zijp, H.J. Nolthenius and H.Ch. Rieffe. Damage cross-section library DAMSIG81. Report ECN-104 (Netherlands Energy Research Foundation ECN, Petten, November 1981).

121 W.L. Zijp, H.J. Nolthenius and H.Ch. Rieffe. Cross-section library DOSCROS81 (in a 640 group structure of the SAND-I1 type. Report ECN-111 (Netherlands Energy Research Foundation ECN, Petten, December 1981 ) .

* 131 W.L. Zijp, H.J. Nolthenius, E.M. Zsolnay, E.J. Szondi, G.C.H.M. Ver-

haag, D.E. Cullen and C. Ertek. Interim report on the REAL-80 exercise. Report ECN-82-065 (also issued as report BME-TR-INT-1/82), (Netherlands Energy Research Foundation ECN, Petten, May 1982).

- T I . Xeactor Dhysics a t t h e I n t e r u n i v e r s i t y Xeactor ~ r ' . s t i t u t e , D e l f t

Reaczor n o i s e measurements i n t h e Dodewaard 3LX have been cont inued,

w i t h emphasis on t h e i d e n t i f i c a t i o n of n o i s e s o u c e s by means of auto-

r e g r e s s i v e (AR) a n a l y s i s techniques and :he detenination of t h e at-power

r e a c t o r t r a n s f e r f u n c t i o n from space-dependent c o h e r e x e of s i g n a l s from

in-core d e t e c t o r s 1 1 1 . R e s u l t s i n d i c a t e t h a t t h e t r a n s f e r f u n c t i o n and

n o i s e sources of t h i s n a t u r a l c i r c u l a t i o n B i i depend on power l e v e l and

c o n t r o l rod p a t t e r n . Experience shows t h a t t h e AR method should be handled .

w i t h g r e a t c a r e i n o r d e r t o o b t a i n p h y s i c a l l y meaningful r e s u l t s . This

orobiem deserves f u r t h e r a t t e n t i o n , because t h e r e i s a t p r e s e n t no c l e a r -

cu t r e c i p e f o r s u c c e s s f u l AR-anaiysis of complicated systems. A Tvin Se l f

?owered Gvnoa De tec to r has been cons t ruc ted f o r 3 S i measurements i n t h e

near f u x r e .

0 . .

The p rev ious ly r epor t ed work on n o i s e i n a ~ y s ~ s of :he 2 3 4 pool type re- ! I

accor HOR was publ i shed 1 2 ; , a s w e l l a s a i s p e r on t h e i n t e r p r e t a t i o n of . . i n c o r e n o i s e 2easuremer.ts i n 3kX's 14 j . The Delf r gr3up p a r t i c i p a t e c rr;

t h e f i r s t n o i s e benchmark t e s t , a s r e p o r t e e i n t h e proceedings of t h e

t h i r d S p e c i a l i s t s ' Xeet ing on Re2ctor Y O ~ S E a t Tokyo !31 .

". ;he des ign f o r an ia-core loop f o r s tudying b o i l i n g ?henorsera i x a 3 e1e&

t r i c a i l y heated dumy F R - t y p e f u e l e imen: was completed. This experhen:

w i l l be baciced up by measurements i n an i d e n t i c a l out-of-core b o i l i n g

loop, i n which d e t e c t i o n nethods can Se used fo r .wh ich 2 s t r o n g r a d i a t i o n

f i e l d i s p r o h i b i t i v e .

A f i n a l p u b l i c a t i o n on previous Xonte Carlo work was i s sued / 5 1 t o g e t h e r

wi th a d e s c r i p t i o n of t h e computer code FOCUS 5 . I n connect ion w i t h

t h i s work an improved xethod was developed f o r handl ing c o n t i n u a in-

e l a s t i c neu t ron s c a t t e r k g i n n u c l e a r d a t a s e t s , which w i l l be publ i shed .

/ i 1 E . B . J . K l e i s s , D e t e m i n a t i o n of 3 k i I a c o r e ?ower Teedback E f f e c t s by Radia l Coherence Xeasu rmen t s . Progr. Nucl. Energy - 9 0 9 8 2 ) 663-675.

121 3.E. :iocgeqSoom, E. van Dam, E.E.J. E e i s s , G . C . van U i t e r t and '5. Veldhuis. D e t e r a i n a t i o n of Xoise Sources and Space-Dependent Re- a c t o r Tzansfer Funct ions from "easured c u t ? ~ : S igna l s Only. ? rogr . Nucl. Energy - 9 (1982) 279-291.

131 N . Suda, Sumary Re?ort on 2 e a c t o r ?ioise Ana?ys is 3 e n c h a r k Tes t . Yrogr. Yucl. Energy - 9 (19823 691-699.

14 / 3 . van Dam, I n t e r p r e t a t i o n of Inco re Xoise Xeasurements i n 3hiuR's. I n v i t e d ?2?er V I . Wis senscha f t l i che Konferenz f;r E n e r g i e w i r t s c h a f t , Z i t t a u (3DR), Xay 1982.

151 J.E. Hoogenboom, A practical adjoint Monte Carlo technique for fixed source and eigenfunction neutron transport problems. Nucl. Sc. Eng. 79 (1981) 357-373.

16 J.E. ~oogenboom~~orn~uter code abstract FOCUS. Nucl. Sc. Eng. 79 (1981) 433. -

111. Reactor Physics Development at E M A (Arnhem)

For three fuel elements the rating distribution in these elements has

been measured by y-scanning for the isotopes Zr-95, Pr-144 and Cs-137.

The elements resided one year in the reactor and contained respectively

- 2 pins 1% Gd, 3 pins 2% Gd and 4 pins 2% Gd. The quality of the rating

distribution has been very good. The measurements show a high internal

consistency. The case with 4 pins 2% Gd has two adjacent Gd pins similar

to the NEACRP benchmark case.

Isotooic correlation .................... Measurements have been performed on the Rh-106fPr-144 correlation,

which can be used as a burnup monitor.

The KEMA is developing a reactor simulator for training of the operators

of the Dodewaard nuclear power plant (50 MW BWR).

The neutronic part of the simulator will be a combination of a fast 3D-

static solution of power distribution of the whole core (6 axial nodes

for each control rod cell) and a point model of the kinetic equation.

The 3D-OD combination is in the testing phase, which is also the case

for the thermohydraulic part of the simulator.

The code that performs the optimization of the fuel loading for the

Dodewaard core has been extended to three dimensions. It was found

that in the optimization the three dimensional rating distribution

should be explicitly taken into account as the position of the control

rods has a marked effect.

Short running times have been accomplished.

NORWAY

STATUS REPORT TO SEACRP

(1981 - 19821

Reactor physics activities in Norway,


Compiled by T. ~kardhamar

- Institute for Energy Technology

N-2007 Kjeller, Norway

1. FMS CODE SYSTEM

Reactor physics activities at the Institute has for many years

concentrated on the development of the modular code system

FMS (Fuel Management System) for light water reactor calcula-

tions. The basic modules of FMS are: the LWR fuel assembly burnup and data generation code RECORD, the 3-dimensional

simulator PRESTO, and the 1- to 3-dimensional RAMONA codes f transient analysis. The system has reached a high degree of

P maturity after the years of development and continuous appli- '

cations by power utilities and other organisations in Europe

and the USA.

As a consequence of the Institute's policy of reducing its

nuclear energy activity, the Institute has in 1981 decided

that future development and maintenance of the whole FMS is,

as from 1982, the responsibility of the international con- sulting company Scandpower A/S, Kjeller, who has been associ-

ated with the application and development of FMS since its

first commercial applications in 1972.

1.1 Status of RECORD

The latest production version of the RECORD code, containing

the model extensions reported in the previous status report,

has been used in benchmarking work by Scandpower A/S and by

one power utility. The analysis of five BWR operating cycles

have been rerun with new data banks generated by RECORD. For

all cycles analyzed, the new version of RECORD shows improved

results over older calculations of reactivity and nodal powers.

In particular, the new treatment of void dependence has in

- some cycles markedly improved the power distribution calcula-

tions in comparison with measured TIP data.

A new option has been introduced into RECORD to be able to

handle the new internal water cross fuels from ASEA-ATOM and

Westinghouse. Comparative analysis have been made to study the

gains obtained for this fuel design. Also included now in

RECCRC ss a permanent feature is the calcx?aticn cf kicetic parameters for use in transient analysis with the RAMONA codes.

A Topical Report has been written describing the methods of

the RECORD code and reviewing the code qualification against measured data. This will be published as a Kjeller Report.

1.2 Status of PRESTO

A number of improvements and new features have been added to

the BWR version of the PRESTO code. These include incorporation

of:

- improved 1/4-core to full-core automatic expansion

capability,

- capability for cold calculations with one or mo.re

assemblies replaced by water,

- fuel temperature calculations allowing for fuel type

and exposure dependent data,

extension of code to allow for 25 axial nodes,

extension of cold condition control rod model to allow

rod worth to depend on exposure and exposure-weighted

void,

slightly adjusted slip correlation to improve the

agreement with FRIGG loop data at high voids,

new and more detailed model for bypass boiling,

improved input and output features. a A PBR code version is available which includes boron criticality

search and automatic boron let-down calculations. Special edits

for the 4-nodes per assembly representation are also imple-

mented.

Studies on on-line version of PRESTO are continuing. A special version of PRESTO has been installed on a VAX-11/780 computer

in the USA. Test runs show that running-times are only a factor

1.4 larger than on a CYBER-175.

The documentation of the code has been extended with a.Topic

Report describing the methods and general qualification of the

BWR version of PRESTO.

1.3 Status of RAMONA

In previous status reports have been described extensive develop-

ment work and applications of the three dimensional dynamics

code RAMONA-111. The code, which is now considered operational,

is being applied by several organisations to different transient problems. RAMONA-I11 is intended 2s a reference code for

analysis of many types of transients where lower order codes

are not directly applicable.

2 . REACTOR PHYSICS ACTIVITIES AT THE OECD HALDEN REACTOR PROJECT

With in t h e Halden P r o j e c t , t h e a c t i v i t y on r e a c t o r p h y s i c s

has been c o n c e n t r a t e d on t h e development of t h e c o r e s u r v e i l -

l a n c e system SCORPIO. A p r o t o t y p e i n t e n d e d f o r i n s t a l l a t i o n

a t PWR power p l a n t s i s a t t h e m o m e n t o p e r a t i n g a t t h e Halden

computer l a b o r a t o r y . T h i s p r o t o t y p e c o n t a i n s a t p r e s e n t no

p r o c e s s c o u p l i n g module, b u t can by u s e of a n e f f e c t i v e c o r e

s i m u l a t o r p r e d i c t t h e d e t a i l e d c o r e s t a t e d u r i n g a n t i c i p a t e d

power t r a n s i e n t s . Much we igh t h a s been p u t on d e s i g n i n g t h e

system f o r u s e by t h e r e a c t o r o p e r a t o r i n t h e c o n t r o l room.

The d a t a base i s c a p a b l e o f s t o r i n g l a r g e amounts of d a t a

which can be r e t r i e v e d v e r y q u i c k l y f o r d i s p l a y on c o l o u r

C R T ' s . A l s o , one has t r i e d t o s i m p l i f y i n p u t s p e c i f i c a t i o n

by e x t e n s i v e u s e of a f u n c t i o n keyboard and a d i a l o g u e s p e c i -

f i c a l l y deve loped f o r t h i s pu rpose . An op t ima l power d i s t r i - L..+ ,ULA,c 4 A c c n z r o l method has been t e s t e d and w i l l be implemented

i n SCORPIO a t t h e b e g i n n i n g of 1983.

SPAIN

REACTOR PEYSZCS ACTIBi%S I K SPAID!

1. SWIXMING-POOL REACTOR DESIGN

Extensive work in this field proceeded at JEN, mainly (1) related to the design of the proposed 3-MWT Ecuatorian Reactor ,

for which a full optimization study was previously done (see

past-year report).

The design effort covered inany areas. In the Reactor

Physics area, calculations have been performed for the various

aspects and items' specifically:

a) Criticality for fresh and equilibrium-cycle cores, . . ... . ... .with neutron fluxes at irradiation fecilities.

b) Control rod worths (single blades, corrbinations, differen-

tial)., together with nuclear hot channel factors.

C) Reactivity coefficients, kinetic parameters (calculated

using importance weighting), and worths of geometry alte-

rations.

dl Core thermal-hydraulic analysis, for both forced and na-

tural circulation, in steady state.

e) Core radiation analysis: dimensions of biological shielding,

gamma heating in core structures, etc.

fl Analysis of the reactivity control system: shutdown margiri,

insertion rates, xenon override and stability analysis.

gl Simpler calculations for the design of the storage pooih

for used fuel elements.

h) Important contributions to the Accident Analysis, using

computer codes to model reactivity and other transients.

Models and codes used in the calculations are being checked.

Specifically, neutronic methods, based on codes WIMS-TRACA and

CITATION, have been applied to an international IAEA benchmark

problem ( 2 r 3 ) , with good results.

REFERENCES:

1. L. Mafias e t a l . "JEN-CEEA c o l l a b o r a t i o n i n t h e design of

a r e s e a r c h r e a c t o r and a s s i c i a t e d l a b o r a t o r i e s " . Approved

f o r p r e s e n t a t i o n a t t h e 2nd I n t e r n . Confer. on Nuclear

Technology T rans f e r (Buenos A i r e s , Nov. 1982) .

2. Research Reactor Core Conversion from t h e u se of h ighly

enr iched uranium t o t h e u se of low enr iched uranium f u e l s :

guidebook. IAEA-TECDOC-233, Vienna, 1980.

- 3 . E. MINGUEZ, M. GOMEZ ALONSO. Cdlculos de benchmark para e l

a n 6 l i s i s neu t rbn ico de un r e a c t o r oon combust ible t i p o MTR.

Actas V I I I Reunibn Anual Sociedad Nuclear Espafiola. (Santan-

de r , s e p t . 19821: i n p r epa ra t i on .

2. NEUTRONIC CALCULATIONS OF PWR CORES FOR SUPPORT OF DESIGN

EVALUATION AND REACTOR OPERATIOR.

The Reactor Division of JEN in collaboration with an elec-

tricity uLiility has continued the activity in the nuclear core

design.

The activities in the past year were:

2.1. Fuel Assembly calculations.'

The system of codes PREWIM + WIMS-TRACA + PROWIM genera- tes by an automatized procedure the cross sections and the k,

2 and M parameters, that are necessary for the core calculatioa

by diffusion or nodal codes respectively. That supposes a set

of assembly calculations at different conditions of power den- .

sity, temperature, depletion, etc.

The input data for the WIMS-TilhCA (1,2,3) , code in provi-

ded for all the different conditions by the PFCEWIM code(4), this

procedure simplifies the preparation of the input data and elimi-

nates the external errors.

POSWIM handles the cross sections sets generated by

WIMS, and corrects the diffusion constant of the burnable Boron

rods in order to preserve the reaction rates and the fluxes in

the cell and in its neighbours,

The HETRES code is used to generate the cross sections

in the control rods Ag-In-Cd in the resonance groups with self

shieding effects included.

2.2. Core Calculations.

Two methods have been used:

2.2.1. The detailed diffusion calcu2ations in two groups of ener-

gy with a mesh point per pin, using the VENTURE-TmCA ( 7 t 8 )

cade, is our reference calc~lation.

The new code5 CONAXI and CONCON have been developed to

facilitate the axial synthesis calculation.

CONAXI is the axial diffusion code, and provides the

axial buckling to be used in the quarter core XY calcu-

lation with VENTURE.

CONCON calculates the active core colapsed cross sections

using the fluxes generated in the VENTURE calculation.

These cross sections are used by CONAXI.

2.2.2. The nodal simulator, SIMULA-3 , allowes a tiidimensio- nal model of the core with 4 nodes per assembly and 15

to 35 axial nodes. By this system is possible to following

the nominal and no-nominal conditions of water density,

power density (Doppler and Xenon in equilibrium or tran-

sientl, Boron concentration, Depletion and control rods

insertion.

In the last year the precision of the simulator has been

improved.

- New formalismes for the transport kernels and albedos has been implemented.

2- - ' . - New correlation for the -L :an8 M , calculations.

- More efficient and stable iteration procedure. - Aditional symmetries (1/8.or 1/4 with rotational symme-

try).

The CONCON and CONAXI codes provide the factors of the

transport kernels and the albedos values in an explicit

and rigorous way, using the detailed fluxes from the

diffusion calculation VENTURE. This procedure mades the

simulator avery accurate system for core calculations,

almost as accurate as other more complex and more time

consuming.

The transport kernels and albedos include now the spec-

tral effects and homogenized of the nodes, its values

may be changed with the average water density and with

the depletion.

The MELON (I0) code calculations the coefficients of the

k, and M2 correlations versus water density, power den-

sity, Boron and Depletion. MELON has a new improvement,

including in the correlations the crossing effects:

- Depletion'in the Boron worth and Doppler correlations.

- Water Density in the Boron worth, Doppler and Xenon correlations.

. . 2.3. Validation of the methods and codes 111

The most relevant neutronic parameters obtained by both

methods the detailed method and the explicitly adjusted core

simulator have compared with the latest vendor calculation. We

found a very good overall agreement.

Assembly average and peak rod powers at BOL-HZP for various

rod configurations, agreed within 1 % RElS and less than 3 % ma-

ximum relative difference.

The Boron worth agreed within 2 %. The Differential and

integral rod worths agreed within 5 % in relative difference. a Moderator and isothermal temperature coefficients agreed within'

1 pcmf•‹F. The differences in the critical Boron concentrations

were within I 40 pcm throughout the first cycle.

Recently the methods have been validated through the ex-

tensive comparison of calculated results and measured data avai-

lable from the start-up test and operating'of the Almaraf nu-

clear power plant (900 Mwe PWR). For instance the comparison

was; like the following:

Burnup Power Critical Boron (ppm (Mwd/T) ( % ) Measured Calculated

a REFERENCES.

3 . J.R. ASKEW, F.J. PAYERS, P.B. KEMSHELL, "A General Descrip- tion of the Lattice Code WIMS". J.B.N.E.S. 5, 564 (1966).

2. C. AHNERT, "Programa WIMS-TMCA para cSlculo de Elementos Combustibles. Manual de usuario y datos de entrada". JEN-461 (1980).

3. M.J. HALLSALL, "A S ~ a r y of WIMS-D4 Input Options". AEEW-M- 1327 Gl980).

4. J.M. ARAGONES, "Programa PREWIM para generaci6n de 10s datos completos de WIMS-TRACA para 10s elementos combustibles de PWR". JEN to be publised in 1982.

5. J!M. ARAGONES, C. AENERT, "POSWIM code. JEN to be published in 1982.

6. J.M. ARAGONES, Eucl. Sci. Eng. - 68, 281 (1978).

7. J.R. VENDY, T.B. FOWLER, C.W. CUNNINGHAM, "VENTURE, A code block for solving multigroup neutronic problems applying the finite difference Diffusion Theory aproximation to neutron transport". ORNL-5062 (19751 .

8. C. AHNERT, "El sistema de c6digos de difusi6n VENTURE-TRACA". JEN/TCR/A 10-80 (1980).

9. J.M. ARAGONES, "SIMULA-3". JEN to be published 1982.

10. I.R. OLAVARRIA, "MELON-3", JEN/TCR/A 04-82 (19821.

11. J.M. ARAGONES, C. AHNERT, J. GOMES SANTAMARIA, I.R. OLAVARRIA, "Development and validation of core phisics methods for in-core fuel Management of PWR's". Topical Meeting on "Advances in Reactor Physics and Core Thermal-Hydraulics". Kiarnesha Lake, N.Y. 1982. NUREG-CP-0034. Vol. 1.

3. ANALYSIS OF INERTIAL CONFINEMENT FUSION.

Following with the work reported in theprevious NEACRP

papers, an extensive work was done on the analysis of the problem

of ignition in inertially confined fusion micropellets.

The general aim to consider both the development of new

capabilities in our calculational model (NORMA-CLARA) ( 1 ~ 2 ) and

to do some calculational on the general performance of different

kinds of micropellets, has been adopted like our line of work.

The effect to include the radiation mechanism in our model,

which consider pressure ionization and degeneracy corrections

in EOS and thermal conductivity, has been conclude ( 3 ) , following the work reported 14) in the last year. In this case, the results

on kidder's situation were obtained in two different conditions:

solid-gas, perfect gas, and other material-geometrical conditions

(2 mg Dt - 50 mg Pb) and boundary pulses were considered. No ignition conditions were radied in radiation cases, where the

maximum temperature value in the central zone is a half, aproxi-

mately, of that obtained in the cases without radiation.

The problem to include 2 T's in the thermo-hidrodinamic

code N O M 4 has been aborded and some progrmation has been sta-

blish, but the model is not completely checked. .

Some routines have Seen made to a bord the problem of

stopping power of heavy ions(5). Two different cases are consi-

dered:

- dense plasmes and high-Z, considering a large interval of energy/mass relations of the beam ion,

- solids, with low values of the energy/mass relation.

The general formulation considers bound and free electron

contributions to stopping power in a sinnple way ( 5 ) making use

of some experimental results in the var5ation of the average

ionization potential with the degree of material ionization.

In the second case, a more simplified model is adopted, making

use of the bound component and a simple expresion corresponding

with the LSS model.

Up to now, energy deposition to plasma by fusion born

neutrons has been obtained in a rather detailed way via multi-

group, discrete ordinates, time dependent transport methods,

but energy deposition by charged particles has been considered

in a rather simplified one (local deposition).

In order to obtain more realFstic results in the analysis

of the fuel ignition and born dynamics, a method has been deve-

loped to obtain a rather valid estimate of the actual influence

of energy transport and deposition by fusion charged particles

on such process.

This method is, in a first approach, rather simple, and

consists of an adaptation of the general method used in the

treatment of energy transport 5y neutrons to the case of the

considered charged particles.

For its application appropriate sets of multigroup cross

section and KEREL9 factors have been to be generated as required

by the used transport code (CLARA) u , 2 1

Generation carried out in practice with the developed

0 code (HELION (61 which starting from differential microscopic

relative velocity dependent cross sections given for the inte-

raction between charged particles by the classical Delaye co-

rrected Rutherford formula, and assuming equilibrium (maxwellian)

distributions for the velocities of plasma components, obtains

the desired Legendre kernels and integrated quantities in the

proposed multigroup frame with density and temperature dependence.

Although this scheme suffers of rather restrictive limi-

tations, basically due to the anisotropy present in Coulomb in-

teractions, the obtained results are considered valid enough in

the assesment of the relative importance of the energy transport

by the treated particles as a mechanism of ignition propagation.

A paper has been presented ( 7 ) in the 9th International

Conference on Plasma Physics and Controlled Nuclear Fusi6n ( 1 9 8 2 )

where the different aspects of this subject are discussed.

Finally, some work is being carried out on the analysis

of alternative microsphere designs able to give improve burnup

and energy gains; in this sense, we are using an impulsive con-

cept of target, as pulse adapter, in order to stabish a parame-'

tric study on single and double shell designs. Some improvements

of our model are being considered; so, radiation transport, su-.

prathermal electron transport, instabilities, are important

subjects to consider in the present and future.

REFERENCES . ,

1. VELARDE, G. et al., Afornkernenergie, 32, 58 ( 1 9 7 8 ) . - 2: VELARDE, G. et al., Atomkernenergie, - 35, 4 0 ( 1 9 8 0 ) .

3. LEIRA, G. et al.,l5th ECLIM. Schliersee ( 1 9 8 2 ) .

4. LEIRA, G. et al., X European Conference on Controlled Fusion. Moscow U 9 8 1 ) .

5. PERmDO, M., Stopping power of heavy ions. MEPIO/JEN/TCR/A-12-8 ( 1 9 8 1 ) .

6. OCAqA, J.L., Ph. D. Thesis. UPM. ( 1 9 8 2 ) .

7. VELARDE, G. et al., Analysis of the problem of ignition in inertiaily confined fusion micropellets. 9th ~nternatioa nal Conference on Plasma Physics and Controlled Nuclear Fusidn ( 1 9 8 2 ) .

4. SHIELDING.

In order to dispose of a sufficient amount of tools in

shielding area some codes and libraries have been implemented

in this period.

The DLC-2/100G library has been tested for the JEZEBEL

benchmark.

The version ANISN-JEN. has been improved with subrou-

tines for dynamic storage allocation for-the UNIVAC 1100 at

JEN. The same subroutines were introduced to the recently ver-

sion'received of DOT 3.5/E (2) code.

On the other hand, some work has been made on the Monte- (3 1 Carlo KENO IV CC& version, w i t h which several criticality calcu-

lations have been performed for the design of a shipping cask.

The SWAN LAKE'^' code has also been tested and implemented. An extensive work on sensitivity area is going to be

undertaken in the next future.

REFERENCES.

1. J. PERA, "Manual para el usuario de la nueva versi6n del programa ANISN-JEN". MEMO JEN/TCR/B 04-81 (1981).

2. F.R. MYNATT et al. "The DOT-I11 Two-Dimensional Discrete ordinates Transport Code". ORNL-TM-4280 (1973).- Updated Oct. 1976 (DOT.3.51. RSIC-Code Collection.

3. L.M. PETRIE, V.F. CROSS, "KENO IV. An Improved Monte Carlo criticalitu Program". ORNL-4938.

4. D.E. BARTINE et al., "SWANLAKE, A Computer Code Utilizing ANISN Radiation Transport ~alculations for Cross Section Sensitivity Analysis", ORNL-TM-3809 (1973).

5 . SHIPPING CASK.

A nuclear criticality safety analysis of a shipping cask

for transport and storage of spent fuel has been carried out.

The discrete ordinates XSDRN code was used to generate

zone averaged multigroup cross sections, the K-effective calcu-

lation was performed with the Monte Carlo KENO IV ( 2 ) code.

i In order to achieve the required subcriticality (Keff(0.93)

the cask in designed.to contain black absorbers.

The thermal safety analysis is being carried out by the

retical and experimental heat transfer studies. P The internal &cay heat frgn s m t M s will be transfered by

radiation and conduction to the exterior surface of the cask.

Natural convection is not given credit.

The heat transfer from the spent fuel elements to the basket

has been only assumed by radiation, according to ats son(^)- The basket and the vessel transfer the decay heat radially by conduc-

tion. Finally the heat is transfered from the external surface,

provided with fins, to the environment by natural convection and

radiation.

The computer code HEATING 5 (4) is being used to calcula

the temperatura distribution in the fuel elements, basket and

vessel.

REFERENCES.

1. J.M. ARAGONES. "Caracterlsticas y utllizaci6n de la nueva versi6n 3 del programa XSDRN". MEMO ;liiEN/TCR/A 79-09 (1979).

2. L.M. PETRIE, U.F. CROSS, "KENO, IV. Arn Improved Monte Carlo Criticality Program". ORNL-4938.

3. J.S. WATSON, "Heat Transfer from Spenk Reactor Fuels During Shipping. A Proposed Method for Predicting Temperature Dis- tribution in Fuel Bundles and Comparison with Experimental Data". ORNL-3439.

4 . S.S. CLARK et al., "A General Purpose Three Dimensional Heat Transfer Computer Code". Gulf General; Atomic, G.A. 9263.

6. .TWO COUPLED CORES REACTOR DESIGN

JEN has been working last year on a research reactor

design for the proposed Soria Nuclear Center; an option is

based on two PWR's small cores with a neutronic coupling by

heavy water or graphite. Geometric optimization has been com-

pleted and a separation of thirty centimeters has been obtai-

ned.

Neutronic flux distributions in.2-D calculations have been

completed with interesting results'') ; these studies have been

a carried out with the WIMS-TRACA ( 2 ) and CITATION computer codes,

also preliminary results about burn-up calculations.

Analysis of temperature distributions have been accomplished

in theirs previous steps. Studies have been made with a 5 % en-

richment fuel, uranium dioxide. The reactor rated power was five

megawatts, available to district heating and biomass studies.

REFERENCES :

1. R. CAR0 et al. "Cdlculos neutr6nicos de un reactor de expe-

rimentaci6n de dos ndcleos acoplados". Actas VIII Reuni6n

e Anual Soc. Nucl. Espaiiola. (Santander, septiembre 1982).

. 2. C. AHNERT. "Programa WIMS-TRACA para el cdculo de elementos

combustibles. Manual de usuario datos de entrada". Report

JEN-461 ( 1 9 8 0 ) .

7. METHODOLOGY VALIDATION FOR THE DETERMINATION OF FLUENCE

IN PRESSURE VESSELS OF LWR'S.

An attempt on the validation of methods and analytical

tools for the determination of neutron fluence in pressure

vessels of comercial LWR's is being made. Particularly, some

calculations are being performed with EURLIB ( 2 ) library and

ANISN'~) and DOT 35/E (4) codes for the PCA "blind test" (1)

The method is based on a spatial flux syntesis, obtaining

reation rates for several ex-core detectors from the dosimetry

file of ENDF~B-IV and calculated fluxes.

REFERENCIAS.

1. Technical Letter for the PCA "Blind Test". L. MILLER et al. Oak Ridge National Laboratory. May 1979.

2. J. PERA, "EURLIB: Una librerfa acoplada de secciones efica- ces para neutrones y gammas especlfica para c5lculos de blin- daje". MEMO JEP;/TCR/A 01-81 (1981).

3. J. PERA, "Manual para el usuario de la nueva versi6n del programa ANISN-JEN". MEMO JEN/TCR/B 04-81 (1981).

4. F.R. MYNATT et al., "The DOT-I11 Two-Dimensional Discrete Ordinates Transport Code". ORNL-TM-4280 (1973) . Updated Oct. 1976 (DOT 3.5). RSIC-Code Collection.

SWEDEN

STUDSVIK ZNERGITEKKIK AB 1982-09-08

K i m Ekaerc, ed

Reactor Phys i c s i n Sweden

S t a t u s Xeport f o r NEACW

1 INTRODUCTION

The t o t a l e f f o r t i n r e a c t o r p h y s i c s remains a t

abou t t h e same l e v e l . S t u d i e s on advanced

r e a c t o r s and f u t u r e f u e l c y c l e s , a s w e l l a s on

wasre t r a n s m u t a t i o n c o n t i n u e . For LWR work has

been done on code development and on n u c l e a r

e a t 2 l i b r a r y benchmarking. A s p e c i a l s tudy hzs

been made on t h e f e a s i b i l i t y of reduc ing t h e

enr ichment of t h e f u e l i n t h e R2 r e s e a r c h

r e a c t o r from 93 t o 2 0 % U-235. A t Chalmers

U n i v e r s i t y of Technology some expe r imen ta l and

t h e o r e t i c a l s t u d i e s have been performed.

2 FUEL CYCLE PROBLEMS

2.1 Neutron d a t a work

Eva lua ted d a t a from d i f f e r e n t s o u r c e s f o r a

number of a c t i n i d e s have been p roces sed i n a

f i v e g r o u p energy s t r u c t u r e . T h i s work was done

f o r t h e Swedish Nuclear Data Committee a t t h e

NEA Data Bank, Sac lay .

2.2 Benchmar.king of 2 CASMO/CPM 69-group

n u c l e a r d a t a l i b r a r y based on ENDF/B-5

A 69-group n u c l e a r d a t a l i b r a r y based on

ENDF/B-5 has been t e s t e d by i t s a p p l i c a t i o n i n

c a l c u l a t i o n s on v a r i o u s c r i t i c a l expe r imen ta l

c o n t i g u r a t i o n s . Most of t h e expe r imen t s , some of

which i n c l u d e nixed-oxide f u e l , c o n t r o l r o d s and

bu rnab le a b s o r b e r s , had been c a r r i e d o u t i n t h e

? . high- tempera ture z a c r l ~ t y K R l T Z a t STUDSVIR,

Sweder..

The c e l l c a l c u l a t i o n s , which concern p i n c e l l s ,

a s w e i l a s BW4 and ?WR assemblies, were pe r -

formed w i t h t h e c r a n s p o r t t heo ry code CASMC.

Four-group d a t a from CASMO were then used i n a

d i f f u s i o n t h e o r y code D I X Y f o r t h e c o r e c a l c u l a -

t i o n s .

The agreement between c a l c u l a t e d and measured

r e s u l t s i s i n g e n e r a l a c c e p t s b l e bo th f o r t h e

k e f f v a l u e s and f o r t h e F i s s i o n r s t e d i s t r i b u - @ t i o n s . For i n s t a n c e , more t h a n h a l f of t h e ke f f

v a l u e s , 4 9 a l t c g e t h e r , a r e b - i t h in 0 . 5 % from

u n i t y , t h e expe r imen ta l r e s u l t .

The main conc lus ion i s t h a t t h e t e s t e d l i b r a r y

i s adequa te f o r c a l c u l a t i o n s on unburned l i g h t

wa te r r e a c t o r c a s e s w i th U02 o r PuO f u e l . Some 2 p o s s i b l e d e f i c i e n c i e s i n t h e l i b r a r y , i n t h e

f i r s t p l a c e a f f e c t i n g t h e r e a c t i v i t y c a l c u l a -

t i o n s , can however be i d e n t i f i e d . I n p a r t i c u l a r ,

t h e e f f e c t i v e resonance i n t e g r a l of U238 comes

o u t about 3 % t o o l a r g e i n t h e c a l c u l a t i o n s . a T h i s work, performe* under an EPRI c o n t r a c t , was '

s t a r t e d i n mid-1980 and was concluded i n t h e

beg inn ing of 1 9 8 2 . A p a p e r , b e i n g a condensed

v e r s i o n of a forrhcoming EPRI r e p o r t , was p re -

s e n t e d a t a conference o r thermal r e a c t o r bench-

mark work he ld a t Brookhaven i n May, 1982.

2 . 3 Reac tor p h y s i c s c a l c u l a t i o n s on c l o s e -

packed LWR l a t t i c e s

A c a i c u l a t i o n a l p r o j e c t has been s t a r t e d d e a l i n g

w i t h c lose-packed l a t t i c e s i n LWRs - i n p a r t i c u -

l a r i n PWRs. Such l a t t i c e s , i n e s sence d r i v e n

- 117 -

STUDSVIR ENERGITEKNIK AB

w i t h p l u t o ~ i u m and having a modera tor - to - fue l

volume r a t i o of about 0 . 5 , would g i v e convers ion

r a t l o s around 0 . 9 .

So f a r t h e c a l c u l a t i o n a l method, i . e . t h e c e l l

code CASMO, has been t e s t e d a g a i n s t exper imenzs

from t h e USA and a l s o a g a i n s t c a l c u l a t i o n s w i t h

t h e f a s t - r e a c t o r code EQUICYCLE. The outcome of

t h e s e t e s t s i s a c c e p t a b l e .

Some c a l c u l a t i o n s on power r e a c t o r c a s e s ,

p r e v i o u s l y s t u d i e d i n t h e FRG, have a l s o been

done. Our r e s u l t s t h u s f a r o b t a i n e d a r e l e s s

f avourab le t h a n t h e German ones .

The work t h u s f a r done i s d e s c r i b e d i n STUDSVIK

Report NR-82/126 by E. Johansson.

2 . 4 C a l c u l a t i o n s on t h e change from 93 %

t o 2 0 % e n r i c h e d uranium i n t h e R 2

r e s e a r c h r e a c t o r

According t o p r e s e n t p l a n s t h e R2 r e a c t o r w i l l ,

be d r i v e n w i t h 2 0 % e n r i c h e d uranium from abou t

1 9 8 6 and on. I n t h a t c o n t e x t a c a l c u l a t i o n a l

p r o j e c t h a s been s t a r t e d , s o f a r mainly d e a l i n g

w i t h r e a c t o r p h y s i c s consequences of t h i s

enr ichment change from 9 3 % t o 2 0 % . A l a r g e '

p a r t of t h e work done d e a l s w i t h t e s t s o f t h e

codes i n v o l v e d , i . e . t h e c e l l code CASMO, t h e

two-dimensional d i f f u s i o n theo ry c o r e code D I X Y ,

t h e th ree-d imens iona l s y n t h e s i s c o r e code TRESYN

and t h e th ree-d imens iona l LWR burnup c o r e code

POLCA. These t e s t s , coming o u t reasonably w e l l ,

i n c l u d e comparisons w i t h r e s u l t s f rom f o r e i g n

c a l c u l a t i o n s on an IAEA benchmark c a s e a s w e l l

a s w i t h expe r i emen ta l r e s u l t s from t h e R 2 r e a c -

t o r .

Concerning t h e f u t c r e s p e r a ~ i o c of R 2 w i t h 2 0 %

e n r i c h e d f u e l a st .x?y t a s been done on t h e pre -

s e c t 44-element c o r e v i t h a somewhet modif ied

f u e l e lement . The new elemect chosen c o n t a i n s 1 7

f u e l p l a t e s each wi:h C.10 cm tn i ck :DAl meat 3 X

ho ld ing 2 . 6 gU/cm ( p r e s e n t v a l u e s a r e 1 9 , 0 .051

and 0 . 7 3 ) . The burnup would cor respond t o a

d e c r e a s e of t h e U235 c o n t e n t by 55 %. The f u e l

c y c l e l e n g t h would be 31 days (now it i s 11

d a y s ) . The the rma l neu t ron f l u x on t h e c e n t e r

a x i s of an e x p e r i m e c t e l p o s i t i o n v c . ~ l d be about

85 % of t h e v a l u e f o r t h e o r e s e n t 93 % e n r i c h e d

c o r e .

The work i s d e s c r i b e d i n STUDSVIR Report

NR-82/136 by R Eoglund and Z Johansson.

2.5 The Thorium Fue i Cvcle

A r e p o r t on t h e s t z t e - o f - t h e - a r t of t h e thor lum

f u e l c y c l e has bee r comprled. The emphasls i s on

t h e HTR an2 CANDU r e a c x o r s .

F u r t h e r s t u 2 i e s on thor ium i n CANDU a r e be ing

performed i n coope ra t ion w i t h A X L i n Chalk

River . Burnup c a l c u l a t i o n s a r e c a r r i e d o u t t o a

conf i rm t h a t an expec t ed convers ion r a t i o of

about 1 . 0 can be o b t a i n e d .

3 POWER REACTORS

3 . 1 Code development

The 2D d i f f u s i o n code MSS has been t e s t e d on

v a r i o u s problems.

The pre -s tudy of a Fue l Management System a t

SSPB has been e v a l ~ a k e d . The development of such

a system w i l l be c a r r i e d o u t s tep-wise wh i l e

STCDSVIK ENERGITEGNIK A3

main ta in ing o p e r a b i l i t y of each component of t h e

system.

A new v e r s i o n . CASMO-2, has been r e l e a s e d of t h e

well-known c e l l and zssembly code. The new

v e r s i o n i s compat ib le w i t h t h e p rev ious one , b u t

o f f e r s many more o p t i o n s . e s p e c i a l l y f o r PWR

a p p l i c a t i o n s .

4 NEUTRON PHYSICS

(Department of Reactor Phys i c s , Chalmers Univer-

s i t y of Technology, Goteborg, Sweden)

4 . 1 Exper iments

The measurements of t h e neu t ron s lowing down

t i m e i n wate r sys tems of d i f f e r e n t s i z e s have

been completed /I/. S i x ~ u b e s of wate r w i t h s i d e

l e n g t h s from 8 t o 3 C cm were used. Neutrons ge-

n e r a t e d i n p u l s e s of about 1 n s were slowed down

from 1 4 MeV t o t h e indium resonance a t 1 . 4 6 eV

and were d e t e c t e d xhrough t h e c a p t u r e gamma

r a d i a t i o n . The most p robab le s lowing down t i m e s

were found t o be 7 7 8 + 23 ns and 8 9 8 + 25 ns f o r - - t h e s m a l l e s t and f o r t h e l a r g e s t of t h e cubes ,

r e s p e c t i v e l y . The expe r imen ta l r e s u l t s f o r t h e

s i x cubes were compared t o t h e s lowing down

t imes o b t a i n e d from v a r i o u s t h e o r e t i c a l

approaches and from Monte C a r l o c a l c u l a t i o n s . I n

a l l c a s e s a d e c r e a s e of t h e s lowing down t ime

w i t h d e c r e a s i n g s i z e of t h e moderator was found.

The e f f e c t was l e a s t pronounced i n t h e

expe r imen ta l r e s u l t s .

The energy d i s t r i b u t i o n of D-D n e u t r 6 n s from

s o l i d deu te r ium- t i t an ium t a r g e t s h a s been

measured by means of a Be-3 spec t rome te r / 2 / .

The observed s p e c t r a a r e s t r o n g l y i n f l u e n c e d by

t h e s lowing down p r o c e s s of t h e d e u t e r o n s i n t h e

- i ~ r g e t . I n f a c t , t h e c o n c e n t r a t i o n of deu te r inm

a s a f c n c t i o n of r z r g e r deprh can be o b t a i n e l

from t h e neasureme-zs. A l a r g e d i f f e r e n c e was

found between a f r e s h and a h e a v i l y used t a r g e t .

The method of measurement c o c l d be a he l ? i n t h e

e f f i c i e n t u s e of t h i c k t a r g e t s f o r neu t ron

p r o a u c t i o n .

4 . 2 Theory and computat ion

The accuracy oq an A N I S N program ( o b t a i n e d from

t h e NEA d a t a bank) an2 of an i n t e r n a l l y deve l -

oped S proqram CTBSN / 3 / has Seen t e s t e d on n some benchmark problems of neu t ron t r a n s p o r t / 4 /

w i t h one o r two groups of - r - t r o n s and wi th up

t o t h r e e d i f f e r e n t n e l i a . I n g e n e r a l it i s found

t h a t t h e agreement between ANISN and CTHSK snd

between t h e s e programs and o t h e r c a l c u l a t i o n

methods w i t h s i m i l z r accuracy i s w i t h i n 1 p e r

m i i l e o r S e t t e r . Except ions occu r c l o s e r t h a n 1

mfp from a l o c a l i z e 6 source and f o r problems

w i t h media of ve-ry d i f f e r e n t p r o p e r t i e s . The

ANISN program has bee2 used f o r s h i e l d i n g c a l c u -

l a t i o n s / 5 / and f o r p r e l i m i n a r y work on t h e

u s e f u l n e s s of neu t ron c a p t u r e t h e r a p y / 6 / . a

STUDSVIK ENERGITEKKIK AB

4 . 3 References

i . S Hi r schbe rg , CTH-RF-37 ( 1 9 8 1 ) t o be p u b i i s h e d i n Ann. Nucl. En.

2 . K H Beimer and G Grosshog, Proc . S s c . I n t . Symp. on Rad ia t ion P h y s i c s , Malaysia (1982)

3 . N G S j o s t r a n d , Ann. Nucl. En. 7 , 435 (1980)

4 . M A Etemad CTH-RF-39

5 . M A Etemad

6 . M A Etemad CTB-RF- 4 1

and N G S j o s t r a n d 1981)

CTH-RF-40 (1982)

and N G S j o s t r a n d 1 9 8 2 )

EACTOR PHYSICS ACTIVITIZS IN SWITZEP.LAND

October 1981 to Septenher 1962

P. Wydler

1. Introduction

In 1982 the proposed Kaiseraugst plant has continued to be the dominant

issue on the Swiss energy policy scene. After prolonge? debates the

Federal Council has finally approved the plant. This decision is now

awaiting confirmation by the Parliament. The olitical situation is further

complicated by the fact that two new anti-nuclear initiatives have recent-

iy been laid before the Federal Council. A referendum is expected to take

place in 1984.

Meanwhile the four operating plants (3 PWRs, 1 BWR) continue to generate

electricity at very high load factors (over 85 % on average in 1981).

Construction work at the site of the 942 MWe ieijstadt plant, which is

being equipped with a General Electric BWR-6, is nearing completion, and

the plant is expected to go into operation in 1384.

As e result of the current political situation the Swiss nuclear energy a

programmes are heavily biased towards the backend of the fuel cycle,

leaving only limited funds for reactor physics work. For 1982 the Federal

Institute for Reactor Research (EIRI has a research budget of 42 MSFr.

(million Swiss Francs). Of this 2. 3 MSFr. are allocated to reactor

physics programmes. With the aim to support Swiss reactor operators

2. 0.8 M SFr. are spent for (mainly analytical) LWR related physics

activities. The remainder ('L 2.2 M SFr.) has been concentrated on an

experimental programme at the PROTEUS reactor for determining the physics

properties of Light Water High Converter Reactor lattices. Outside EIR,

fusion-fission hybrid blanket experiments to be performed at the Swiss

Federal Institute of Technology at Lausanne are worth mentioning.

2. LWR Physics Ca lcu la t ions

The E I R Light Water Reactor code system has been used f o r a d e t a i l e d simu-

l a t i o n of cycle 6 of t h e Miihleberg BWR. Over 70 % of t h e cycle k was e f f

overpredicted by a cons tant amount of 1.2 % . Towards t h e end of t h e cycle

t h e dev ia t ion increased t o 1 .8 % . This l a t t e r e f f e c t can be r e l a t e d t o

d i f f i c u l t i e s i n c o r r e c t l y s imula t ing t h e reduct ion of t h e mean void. A

s imula t ion of two s t a r t - u p experiments of t h e Beznau-2 PWR gave very s a t i s -

f a c t o r y r e s u l t s : The observed d i sc repanc ies were l e s s than 0 .3 % f o r k e f f

( o r 30 ppm of boron) and l e s s than 5 % f o r t h e power d i s t r i b u t i o n .

The usefulness of t h e code BOXER has been f u r t h e r extended by a v a l i d a t i o n

exe rc i se f o r LWHCR (Light Water High Converter Reactor) l a t t i c e s using

r e s u l t s from t h e f i r s t core of t h e LWHCR-PROTEUS experiments. Except f o r

captures i n 2 3 6 ~ , good agreement between ca lcu la ted and measured reac t ion

r a t e s i s observed.

The physics analyses of compact s to rage pools have been continued wi th a

s tudy concerning the inf luence of d i f f e r e n t sepa ra t ion p l a t e s between

spent f u e l elements on t h e v a r i a t i o n OL keff with water dens i ty . Borated

and normal s t e e l p l a t e s were found t o have a d i s t i n c t l y d i f f e r e n t behaviour:

For bora ted p l a t e s k decreases oontinuously with decreasing water e f f

d e n s i t y , whereas f o r s t e e l p l a t e s k reaches a maximum a t an in termedia te e f f

water dens i ty . In a p r a c t i c a l case t h e maximum is a t 20 % r e l a t i v e water

dens i ty and t h e r a t i o of t h e maximum k and t h e keff a t 100 % water e f f

dens i ty i s 1.1. The e f f e c t has t o be taken i n t o account i n t h e s a f e t y

a n a l y s i s of t h i s p a r t i c u l a r type of s to rage pool.

3. LWR Pressure Vessel Surve i l l ance Dosimetry

Under c o n t r a c t t o Swiss r e a c t o r opera to r s E I R has a programme f o r de te r -

mining l ead f a c t o r s of ma te r i a l samples and neutron dosimeters i n s t a l l e d

i n PWR and BWR p ressure v e s s e l s (The l ead f a c t o r i s t h e damage o r f luence

ratio between the sample position and the well of the 3ressure vessel).

Lead factors are normally calculated, and the calculational methods are

checked using integral spectrum informatior. srovided by the dosimeters.

Up to now direct measurements of lead factors have not been reported in

the open literature.

A direct measurement of the lead factor under operating conditions has 93m

recently been performed in a 1000 MWe PWR by means of the Nb decay

measurement technique. The inside of the particular pressure vessel is

coated with a layer of IT' doted steel. Nb was chemically separated from

small samples taken from the surface of the vessel and the decay activity

was compared with the activity of Nb dosimeters installed in the vessel.

Special experimental techniques had to be developed to obtain Nb samples

of the required very high purity.

A study was carried out to check whether lead factors are pre6icted adequa-

tely by one-dimensional transport theory. For =he Beznau-l reactor the

azimuthal flux distribution was calculated using the BOXER code with the

two-dimensional transport theory option QP The ratio of the fluence at 1.

the position of the dosimeter to that at the inner surface of the pressure

vessel showed azimuthal variations (relative to the mean value) of ? 20 % .

It is concluded that, in cases where the reactor geometry is cylindricalized,

particular care has to be taken to ensure that calculated lead factors are

conservative.

4. Experimental Studies on LWHCR Lattices

The current programme of measurements on LImCR lattices in the PROTEUS

reactor will come to an end in October 1982. Till June 1982 efforts were

concentrated on obtaining results for a reference lattice consisting of

a 1: 1 mixture of 15 % PuO /UO and depleted UO fuel rods in a tight- 2 2 2

pitch configuration with a fuel/moderator ratio of 2 .0 . In effect three

experimental test zones were considered - with H 0 as moderator, with 2

air (100 % voidage) and finally with Dowtherm (an organic liquid simulating

approximately 45 % H 0 voidage). 2

23OPu The principal core-centre reaction rate ratios measured, relative to

238 fission, were capture in U and fission in 235U, 238U and

241 Pu. Also

measured as spectral indices were infinite-dilution reaction rates for

1•‹B(n,a) and 232~h, 2 3 3 ~ fission. km values were deduced via buckling

measurements (reaction rate traverses) in the •’3 0 and Dowtherm lattices, 2

while for the dry case use could be made of null-reactivity measurements

carried out earlier for a similar configuration in the GCFR-PROTEUS pro-

gramme. A limited set of small-sample reactivity measurements was also

carried out in the LWHCR lattices using cigars of C, steel, etc. Finally, 4

certain whole-reactor reactivity changes were measured, such as during a

moderator dump from the test zone.

In July 1982 the 1: 1 test lattice was reconstructed so as to accomodate

a central 2 : 1 (Pu-rod: 3-rod) zone with a diameter of approximately

20 cm. Calculations showed that reaction rate ratios at the centre were

close to the equilibrium-spectrum values for the higher enrichment (2 : 1)

zone. Measurements of the important ratios will be completed - again with

H 0, air and Dowtherm - by October 1982. 2

Up to now only partial analyses of the measurements have been performed.

Methods applied have included WIMS-D, EPRI-CPM (being investigated

separately under an EPRI research contract) and BOXER. A strong dependence

on the available data options has been observed, C/E (Calculation/Experi-

ment) values being found to differ by upto 10 % for several parameters.

The bulk of the analysis will be completed by mid-1983 and should, when

considered in total, provide useful evidence for the adequacy of cal-

culated reactivity variations with voidage for homogeneous-design LWHCRs.

The total time available for the measurements (14 months) has been a

constraint on the range of configurations that could be investigated. In

view of the uniqueness and the success of the current experiments per-

mission is being sought to embark upon a more detailed experimental pro-

gramme (LWHCR-PROTEUS Phase 11) to be carried out during 1984-87.

5. Fusion-Fission Hybrid Blanket Experiments

Fusion-Fission Hybrid Reactors (FFHRs) have been proposed as an alternative

to Fast Breeder Reactors. It is being speculated that FFHRs are an inter-

mediate sEe? to pure fusion reactors, and that an FFHR could supply fissile

material to a very large number of Advanced Converter Reactors. To check

the adequacy of nuclear data and computational methods for FFHR blanket

applications the "Laboratoire Be Ginie Atomique" of the Swiss Federal

Institute of Technology at Lausanne is planning to perform FFHR experi-

ments in a zero-power facility called LOTUS.

The experimental arrangement consists of a 3-T neutron source with a source

strength of 5 - loLL neutrons/*, a 8 0 ~ thick graphite reflected ThO /Li 2

assembly and the associated shielding. Features similar to a realistic

blanket module have been incorporated in the blanket design and blanket

optimizations have been carried out. The calculations show that the neutron

flux is adequate for performing neutron spectrum, foil activation (mainly 232

Th casture) and tritium production measurements. The neutron source has

been delivered and measurements on the first blanket configuration are

scheduled to begin in Autumn 1983.

- 127 - UNITED KINGDOM

REACTOR PEYSICS IN T3E Z R I T E D KINGDON

J.2. A s k e w and A..T.D. B u t l a n d , Winfrith

- - ~ -. - ... ..

I GENERAL P E O G W

The p u b l i c enqui ry i n t o t h e proposed Sizewell ' B ' PUR w i l l begin i n January 1983 and i s expected t o cont inue i n t o the Autumn.

Extens ive i n s p e c t i o n and t e s t p r o g r a m e s on CEGB Magnox r e a c t o r s have been under taken fo l lowing d e t e c t i o n of d e f e c t s i n p r e s s u r e c i r c u i t components. One r e a c t o r a t each of t h e Dungeness li and Bradwell s t a t i o n s has been re turned t o s e r v i c e and o t h e r s under i n s p e c t i o n a r e expected t o be i n o p e r a t i o n du r ing 1982183.

The a v a i l a b i l i t y of t h e ope ra t ing AGR s t a t i o n s con t inues t o improve, and a r e t u r n t o onload r e f u e l l i n g i s expected i n t h e near f u t u r e . Power r a i s i n g a t - t h e f i r s t u n i t s of t h e Har t l epoo l and Heysham s t a t i o n s i s expected d u r i n g

a t h e coming w i n t e r .

2 THEWAL REACTORS

The RETRAN pres su r i sed f a u l t code has been f u r t h e r v a l i d a t e d a g a i n s t t h e r e s d l t s of t e s t s i n t h e LOFT f a c i l i t y . These inc lude m a l l b reaks L3-5 and L3-6 a s w e l l a s p r e s s u r i s e d t r a n s i e n t L6-I, -2 and -3. The r e s u l t s of t hese comparisons, t oge the r wi th a summary of s t u d i e s of p r e s s u r i s e d f a u l t s on t h e proposed UR FW? were presented t o t h e second i n t e r n a t i o n a l F32TRAS meet ing , A p r i l 1982 i n two papers ( 1 , 2 ) .

The s t e m l i n e break wi th RCCA s tuck l e a d s t o a ve ry a s y m e t r i c poi.ier d i s t r i b u t i o n a s t h e core goes c r i t i c a l on cool ing and r e p r e s e n t a t i o n of t h e feedback i n t h i s a s j m e t r i c case i n t o a ~ o i n t model of t h e core p r e s e n t s d i f f i c u l t i e s . Two dimensional x-y t r a n s i e n t s t u d i e s were performed t o g ive weighting f a c t o r s . ~ ~ .. . . ~ ~

The r e f e r e n c e des ign f o r t h e UK PIJR now inc ludes an emergency b o r a t i o n system (EBS) which se rves a s a d i v e r s e scram mechanism and reduces t h e s e v s r i t y of ATWSevents.

, - . - S t u d i e s of t h e r e a c t i v i t y holddown and burnup of b o r o s i l i c a t e g l a s s poisons have compared p r e d i c t i o n s of a one mesh-pointlpin d i f f u s i o n theo ry model w i th a d e t a i l e d t r a n s p o r t c a l c u l a t i o n u s i n g t h e CACTUS c h a r a c t e r i s t i c s model f o r a 4 x 4 a r r a y inc lud ing one poison p in . R e a c t i v i t y was too h igh by 0.35% u s i n g t h e s imple model, bu t t h i s could be remedied by an a r t i f i c i a l i n c r e a s e i n mean chord of t h e poison a s i l l u s t r a t e d i n F igure 1 . . ~ ~.

F u r t h e r v a l i d a t i o n of t h e CACTUS model has been c a r r i e d out ( 3 ) , i nc lud ing comparisons wi th a range of o t h e r t r a n s p o r t theory s o l u t i o n s inc luding Sn, c o l l i s i o n p r o b a b i l i t y and Monte Carlo methods.

The technique has a l s o been appl ied t o a range of neut ron t r a n s p o r t problems i n complicated geometry, i nc lud ing t h e BhX Gadol in ia benchmark and problems of energy d e p o s i t i o n i n Gas-Cooled r e a c t o r s . F igu re 2 shows t h e geometr ic r e p r e s e n t a t i o n achieved i n t h e l a t t e r case .

F u r t h e r s t u d i e s us ing t h e WIMS 81 d a t a l i b r a r y have con t r ibu ted t o i t s v a l i d a t i o n . A range coverjng va ry ing p i t c h e s , rod s i z e s e t c inc lud ing

- . cases wi th v e r y l a r g e resonance c a p t m e c o n t r i b u t i o n s were s tud ied by Barc lay . ' Thc r e s u l t a n t e igenvalues aire shown i n F igure 3.

- .-.- - . - . . .~ . . ~

. . ~~ .. Extensive redocumentat ion of the iiMS-E ;ode i s we l l advanced, and t h e

d e s c r i p t i o n s of t h e p r i n c i p a l modules have been i ssued i n an u n c l a s s i f i e d form. The Monte Carlo co'de XONI: has been included i n the scheme and has been used f o r whole r e a c t o r s imula t ions u s i n g 69 group P; d a t a f o r s i t u a t i o n s i n which t h e geometr ic complexity i s such a s t o p rec lude t h e u s e of simpler models. The code inc ludes an a d j o i n t o p t i o n .

The LWR-WIPIS/JOSWA code has been used t o s imula t e t h e f i r s t 3 c y c l e s of the UK PWR o p e r a t i o n us ing a 4 x 4 mesh/asseinSly model. This pe rmi t s a b e t t e r r e p r e s e n t a t i o n of non-symmetric loadings of burnable poison i n assembl ies a s i s proposed f o r t h i s r e a c t o r , and pe rmi t s a s impler model of burnup and peak r a t i n g fo l lowing f u e l s h u f f l i n g . A s y n t h e s i s of t h e r a t i n g s produced i n coarse mesh wi th the LF'R-WLYS assembly c a l c u l a t i o n g i v e s s i n r a t i n g s 2nd a code has been w r i t t e n t o p rov ide s t a t i s t i c a l ana lyses of t hese . a

3 FAST EACTORS

. . . o o i n t h e 5 I E T s x 7 e r i z e n t d ? r o g r m n e -shLch sncea x. . k g u s t 1980 t h e , . . - C.4DSSZA (.Compact Assem3~;~ D i a g z o s t ~ : :sperimencs i n Zebr;) ? r z s z m x e was . . .

bepun. This progrmme was designed t o i n v e s t i g a t e t h e over-?rec:cr:cn of . . . . . t i e r e a c t l v ~ r y of pin-geometry asseno!.res r e l a t i v e t o ? ia te -geonet ry r e v e a i e l . . by t h e 3 I Z 2 p r a g r a m e . 'n acccm3anying thecret :cai S ~ C ' J was a l s a znder taken . . . . anc i s S i sc - s sed l a t e r iz r x s ? a p e r .

. * " - . - . . The CAE3Zli ? r ag ran endec i n J u l y , 7 0 2 and -ass rz;,c%ei a shcrz . . . . . . ? r o g r z r r e of ?F3 r e l a t e d -aork, d e s i g ~ e d :a - r a ~ x z z e t5e : a ~ r - ~ a t l o n i ?

. . methods o s e 6 z o 3 r e d i c t rhe h e a i e r p in powers i n the Dernouc;&n;e Subassemblies used i n ?EX t o i r r a d i a t e s t r u c t t l r a l and absorber a a t e r i a l

. . samples. This s tudy was cons idered worthwhile because t2e - e a t e r p i n s l i e i n t n e lower = i a i b r e e d e r , where they r e p r e s e n t a l o c a l ckznge i n m z t e r i a l composition r e l a t i v e t o t h e surrounding breeder m a t e r i a l , a situation which may n o t be c a l c u l a t e d w i t h s u f f i c i e n t accuracy ~~~

by ~ t h e s tandard d i f f u s i o n . ~

a t heo ry methods used f o r PFR.

. ..~.. ~ . . ~- ~ ~.~ ~ . . ~. .. ~ . .~ .. ~ . . - .

Zebia has- now been s h tdobn, but a c o m ~ r e h e 6 s i v e marntenance schedule i s t o be c a r r i e d o u t i n order t o a l low s t a r t u p a t s h o r t n o t i c e . The agreed p o l i c y i s t h a t t h e t o t a l Zebra c a p a b i l i t y should be r e t a i n e d u n t i l t h e CDFR i s a t w advanced s t a g e , so t h a t any i s s u e s which a r i s e ir? t h e d e s i g n or i n t h e f u e l l oad ing , a s s o c i a t e d wi th r e a c t o r p h y s i c s , , can be r e so lved

. ~ . ~.. exper imenta l ly . I n t h e meanwhile the Zebre exper imenta l .... team a:re . moving . . t o c r i t i c a l i t y work a s d i s c ~ u s s e d l a t e r i n t h i s paper .

The CADENZA programe cons i s t ed of four b a s l c z s s e n i l i e s , namely f looded and voided v e r s i o n s of an a l l p l a t e core and f looded and voided v e r s i o n s of a predominantly p i n c o r e . To probe t h e l i f f e r e n c e s between t 5 e two geometr ies a range of measurements was made i n each assembly, i nc lud ing element ~ o r t h s , core c o n s t i t u e n t worths and r e a c t i o n r a t e scans . l-teasuremerts were a l s o made t o a s s e s s t h e i n f l u e n c e of changes i n f u e l - p l a t e h e t e r o g e n e i t y on r e a c t i v i z y and f i n e s t r u c t u r e r e a c t i o n r a t e s . Furthermore t h e changes f r o n the p l a t e t o t h e p i n geometry assemblies were mace i n s i x s t a g e s t o f a c i l i t a r e t h e i n v e s t i g a t i o z s . The voided a s s e c b l i e s were i x i i l d e d t o h i g h l i g h t one a spec t of hecerogenei ry , naae lp :he chscge i n neu t ron SL-,,- LALcmr.g ' brought abcut by :he l o s s of sodium.

g1011013i.

The methods used i.n t h e f i r s t s t a g e a n a l y s i s of t h e CADENZA experiments werebased on XTZ d i f f u s i o n theory models wi th FGL5 d a t a and s tandard one d imens ional c e l l methods t o a l low f o r p i n i p l a t e he t e rogene i ty and neut ron s treaming.

The r e s u l t s c o d i r m t h e BIZET work and demonstrate t h a t t h i s c a l c u l a t i o n a l r o u t e o v e r p r e d i c t s t h e k-va lue of t h e p i n core r e l a t i v e t o t h e p l a t e co re by 0.96%. The u n c e r t a i n t y i n t h i s v a l u e i s 2 0.15 dk/k (1 s d ) , a r i s i n g rcainly from u n c e r t a i i ~ t i e s i n t h e composition of t h e assembl ies . I d e n t i c a l d i s c r e p a n c i e s a r e obta ined both wi th sodium p r e s e n t and w i t h a l l t h e sodium i n t h e core vo ided , i n d i c a t i n g t h a t t h e problen! a r i s e s p r i m a r i l y from t h e f i n e s t r u c t u r e t rea tment of h e t e r o g e n e i t y r a t h e r than from t h e t r ea tmen t of neut ron s t r e a a i n g .

Small s c a l e sodium-void s t u d i e s a l s o confirm t h a t t h e r e i s no s i g n i f i c a n t d iscrepancy i n t h e sodium-void p r e d i c t i o n s f o r t h e two geometr ies , a s implied from t h e k-values observed. Both geometr ies r e q u i r e s i m i l a r f a c t o r s t o b r i n g d i f f u s i o n theo ry p r e d i c t i o n s i n t o agreement wi th experiment , which a r e i n t u r n s i m i l a r t o t h o s e obtained from e a r l i e r conventional co res . There a r e , however, s i g n i f i c a n t d i f f e r e n c e s between t h e s e f a c t o r s and those obta ined when sodium i s introduced i n t o a f u l l y - v o i d e d co re .

As p r e v i o u s l y proposed an NEACRP benchmark, based on t h e CADERZA programne, has now been i ssued ( 4 ) t o f a c i l i t a t e an inter-comparison of h e t e r o g e n e i t y p r e d i c t i o n s .

An in tercompar ison of r e a c t i o n r a t e measuyenents nade by AKL (Idaho 'Fa l l s ) and ACE V i n f r i t h i n t h e p l a t e geometry assembly i s t h e s u b j e c t of a s e p a r a t e NEACRP paper .

3 . 2 BIZET klALLT'SIS

A n a l j ~ s i s of the BIZLT exper iments , perforned i n Zebrc? i n c o l l a b o r a t i o n w i t h t h e DeDeKe o r g a n i s a t i o n s , has cont inued, us ing d i f f u s i o n theory methods c l o s e l y r e l a t e d t o those recommended f o r CDFR. Much of t h e a n a l y s i s i n t h e salt-and-pepper heterogeneous co re d e s i g n , EZC, has been completed and t h e work has been extended t o cover k-values, power d i s t r i b i i t i o n s and sodium-void c o e f f i c i e n t s i n t h e more extreme geometry of t h e s i n g l e annulus des ign , BZD. The conclus ious from both geometr ies a r e broadly s i m i l a r , i n d i c a t i n g t h a t t r a n s p o r t t heo ry c o r r e c t i o n s t o t h e d i f f u s i o n theory c a l c u l a t i o n s a r e c o n s i s t e n t l y l a r g e r than i n convent ional assembl ies .

Large t r a n s p o r t e f f e c t s have been found f o r r e a c t i o n r a t e s i n t h e l a r g e c e n t r a l breeder i s l a n d of BZD. Th i s i s i l l u s t r a t e d i n Table 1 , where t r a n s p o r t e f f e c t s of up t o 18% were found f o r threshold r e a c t i o n s . It i s i n t e r e s t i n g t h a t t h e a p p l i c a t i o n of t r a n s p o r t theory t o t h e r e s u l t s seems t o be more s u c c e s s f u l i n t h e o u t e r r e g i o n of t h e breeder i s l a n d . Furthermore t h e f i n a l C/Es a t t h e c e n t r e of t h e i s l a n d a r e s i m i l a r f o r bo th th re sho ld and non-threshold r e a c t i o n s . It should be noted , however, t h a t t h e magnitude of t h e r e a c t i o n r a t e s a t t h e c e n t r e of t h e i s l a n d a r e cons ide rab ly l e s s than those a t t h e o u t s i d e , by about a f a c t o r of 20 f o r U23S f i s s i o n f o r example. This r e p r e s e n t s a cons ide rab le a t tenuat? 'on , ' so t h a t t h e e r r o r i n t h e C/E could .be p a r t l y accounted f o r by some u n c e r t a i n t y i n t h e exac t p o s i t i o n of t h e measurement. '

The t r a n s p o r t e f f e c t s found i n BZC were somewhat l a r g e r than those found i n BZD, a s might be expected i n a l o c a l l y more heterogeneous s i t s a t i o n .

-. Lne in tercom?ar isoa of c e n t r a l r e a c t i o n r a z e r a t i o measurements, which were made by teams from CES ?lo?, K-iK K a r l s r ~ h e and AE5 Winfri:'r. has beer. brougb: t o a s u c c e s s f u l coficluslon and i s t h e s u b j e c t of a s e p z r a t e hZAW paper .

Measurements made of tb.e b e t a an i g a m a 6eca)- power f r o n 11'235 an? Du239 f i s s i o n f r a g x e n t s fo l lowing i r r a c i a t i o n i n assembly BZD/3 a r e a l s o t h e s i lbject of a s e p a r a t e F-ACW paper .

A niimber of r e a c t i o n r a t e meascemen t s f c r r e a c t i o n s of importance t o s t e e l a c t i v a t i o n i n che primary c c o i a n t c i r c u i t of 2 pover r e a c t o r were c a r r i e d out i n a number of 3IZE' i assembl i e s . These r e s d l t s have been combined wi th measurements made ir, an e a r l i e r Zebra core ( t h e PFR mock-up) and a r e t h e s u b j e c t of a s e p x a t e hqACP2 paper .

Work performed i n t h e BIZET assembl ies t o make i n t e g r a l measurements of Cm242 and Cm244 p roduc t ion from neut ron c a p t u r e by Am241 and Am243 was t h e s u b j e c t of 2 paper presented a t t h e r e c e n t Antwerp conference on n u c l e a r d a t a . The measurements were made ir, bo th f i s s i l e and f e r t i i e zones and were used t o t e s t t h e l a t e s t d i f f e r e n t i a l d a t a e v a l u a t i o n s f o r Am241 and Am243. The C/Ss a r e t y p i c e i l y 0 . 8 5 2 0.02 f o r Cm24i bu i ld -up and 0.96 + - 0.07 f o r b 2 4 L bui ld-up .

a TABLE 1

i 8 0 n from Cdter 1 Cencre of Centra1 ( Edge of Cect ra? Breeder

I - Reaction Xare 1 Breeder I s i and 1slanC

I

I I I T ranspor t I

D i f f u s i o n / Transporr D i f f u s i o n I

Theory Theory Theory I (s.) 1 Theory

Notes - ( a ) The r a d i - s of t h e c e n t r a l breeder i s l a d was 480

(b) The l a r g e s t C/Es wit:? d i f f u s i o n theory ;ere found a t the 80 m ? o s i t i o 2

3.3 DISTRIBUTED HEATING EFFECTS

Gamma hea t ing meamrements i n z e r o power f a c i l i t i e s h a s r e c e n t l y centred around t h e UK c o n t r i b u t i o n t o t h e in tercompar ison of measurement techniques completed i n t h e French Masurca f a c i l i t y a t Cadarache and arouzd an a n a l y s i s of t h e measurements made t h e r e . A s e p a r a t e NEACRP paper d e s c r i b e s a new computer program which w i l l be used i n t h i s a n a l y s i s and i s designed t o model e l e c t r o n mig ra t ion .

A new c a l c u l a t i o n a l r o u t e has r e c e n t l y become o p e r a t i o n a l f o r t h e c a l c u l a t i o n of d i s t r i b u t e d h e a t i n g e f f e c t s i n power r e a c t o r s . I n t h i s r o u t e both g m a and neut ron t r a n s p o r t a r e modelled by d i f f u s i o n theo ry methods i n t h r e e dimensional t r i a n g u l a r - z geometry u s i n g ad jus t ed d i f f u s i o n c o e f f i c i e n t s , l 3 gamma energy groups and 6 neut ron energy groups. Th i s

. rou te w i l l g ive g m a h e a t i n g e f f e c t s t o an accuracy of 15-20% and non-gamma h e a t i n g e f f e c t s t o 6-109, f o r co re , breeder and absorber rod zones, t h e higher u n c e r t a i n t i e s applying a t m a t e r i a l boundaries and i n absorber rod channels . A f u r t h e r c a l c u l a t i o n i s r e q u i r e d t o e s t i m a t e t h e f i n e s t r u c t u r e e f f e c t s w i t h i n t h e b a s i c t r i a n g u l a r - z mesh when t h e s e a r e r e q u i r e d . For a t y p i c a l PFR c a l c u l a t i o n t h e breakdown of h e a t depos i t ed i s a s given 1n Table 2 , which i l l u s t r a t e s t h e importance of gamma d e p o s i t i o n i n n o n - f i s s i l e r eg ions . It has been found t h a t t h e g a m a d i f f u s i o n c a l c u l a t i o n s can be performed t o an adequate accuracy when us ing s i x e q u i l a t e r a l t r i a n g u l a r meshes i n t h e p l an of each hexagonal subassembly.

TABLE 2

TOTAL CH.LVNCL POiiRS Iii TYPIC& PFR SUEASSEW3LIf S; BF.CASD3l~W OF TOTAL POT,.?R

1 T o t a l

Inner co re Outer co re F i r s t row breeder Second row breeder MkII c o n t r o l rod ( I /6 i n s e r t e d ) 4 i nch r e f l e c t o r Empty c e n t r a l guide tube

Breakdown of T o t a l Power

Gamma Eon-Gama

M.B. These f i g u r e s apply t o a t o t a l r e a c t o r power of 600NV(th) - and equ i l ib r ium f u e l composi t ions

. . P o s s i b l e r e a s o n s f o r t h e c i sc repancy betsieen t h e r e a c t l v l t y ? r e d i c t i o n s

of p i n and p l a t e co res h a r e beer, s tud ied =. , - - h e . The ~ s e cf 30 c e i l model l ing . . t echniques i n t h e c o l l l s r o n p r o b a b i l i t y prograrr X3AL have been Lnvestig;:ed f u r t h e r f o r bo:h pip. and p l a t e c e l l s . The r e s a l t s have beer. conpare l w i t h t h e 1D t r ea tmen t used i n e a r l i e r ve r s<ons of 5JRki . T'ne nerj MLlW 3D c o l l i s i o n p r o b a b i l i t y r o u t i n s s have been v a l i d a t e d a g a i n s t Xonte Car lo c a l c c l a t i o n s u s i n g t h e XONK progran .

C a l c u l a t i o n s c a r r i e d o u t f o r t h e CADENZA assembl ies i n d i c a t e t h a t t h e p i n l p l a t e r e a c t i v i t y Aiscrepancy of 0.96% 6k/k obta ined t h e r e u s i n g t h e !D t r ea tmen t reduces t o 0.56% ? k / k us ing t h e 3D t r e a t m e n t . The major change be ing an i n c r e a s e of 0.5% 6k/k i n t h e p l a t e c e l l r e a c t i v i t y , w h i l s t t h e i n c r e a s e i n t h e p i n c e l l r e a c t i v i t y was 0.1% 6k/k . When t h i s e f f e c t was analysed i n more d e t a i l it was found t h a t t h e p l a t e c e l l r e a c t i v i t y i n c r e a s e r e s u l t e d from an i n c r e a s e i n t h e p r o b a b i l i t y of f i s s i o n i n t h e plutonium p l a t e s f o r neu t rons w i t h e n e r g i e s above 1 MeV.

The Zebra 8 s e r i e s of zero leakage p l a t e c e l l s has a l s o been re-analysed usLng t h e 3D z e a t m e n t ir! ?%R4L. The r e s n l t i n g C!E v a l u e s f o r k m a r e g iven i n Table 3.

The use of t h e 3D method inc rease6 t h e c s l c u l a t e 2 L v a l u e s by between 0 and 0.62, bu t chey r e ~ a i n e c x i t h i n :?a of :he ex?e r i ze l t ; l v a l u e s .

l e s t I - ~ x p e r i m e n t a l 1 C/E , Region Er ro r j I

I t has been obserged p rev ious ly t h a t t > e f i n e s t r u c t i l r e w i t h i n che c e l l s i s z n d e r e s r h a t e d by t i e stanAard iD method, the l a r g e s t e f f e c t s be ing seen i n U238 f i s s i o n r a t e scans . The 3D met-od gave some inprovemeilt, though s i g n i f i c a n t e r r o r s r ena ined . Table 4 shows t h e masimm pe rcen tage . . v a r l z t l o E s of U238 f i s s i o n ra:e i n each c e l l .

Ir. t h e case of t h e l anage dose g r a d i e n t f c r t h e r conf i rma t ion i s . . being sought by measuring t h e i n d u c e h c ~ ~ v ~ t y f o r a grou? of t k e s h o l d reactions (Ni58(n,p);Ni58(n,np);Yej4(n,p);Co5F(n,\r;NCn,p on op?os i t e

9 s i d e s of b o t h a c o n t r o l rod m a ? p e r anc a g u i l e t u o e , bo th of i h i c h h2ve been i r r a d i a t e d i n ?BR. T'ne r e s u l t s w i l l be compares wi th c a l c u l a t e d p r e d i c t i o n s . The neasurements a r e be ing made a t a number of a x i a l h e i z h t s .

Work i s a l s o i n hand t o improve our knowledge of t h e N593(n,n1)Nb93m r e a c t i o n , a s t h i s can a c t as 2 good monitor of damage dose and so can be u s e f u l i n f u t u r e experimental s e a d i e s . I n t e g r a l r e a c t i o n r a t e measurements f o r t h i s r e a c t i o n (and f o r t h e Fe54(n,p) r e a c t i o n ) have been made i n t h e BiZET assembly EZD/3. D i f f e r e n t i a l measurements a r e be ing made u s i n g the dynamitron machine a t Birmingham U n i v e r s i t y , r i c h a t a r g e t accuracy of 2 5%. T h i s work should ~ r w i d e t h e d a t a r e q u i r e d t o ensure t h a t t h e Nb33(n,n1) r e a c t i o n can be used a s an e f f e c t i v e moni tor .

3 .6 DEVELOP?fENTS IK NODAL DIFFUSIOE: THEORY FOR bTOE REACTOX CALCLTLATIONS; TRANSPORT THSORY STUDIES

T'ne hexagonal geometry nodal expansion ( . 5 ) d i f f u s i o n theory c o i e XEmCC, r e f e r r e d t o i n l a s t year's ?TC,ACTCD p rogres s r e p o r t , has now been extended t o 3D. . . An impor tant f e a t u r e of :he code i s t h a t :: :s capable cf handl ing nodes w i t h a x i a l d5nensicns m c h l a r g e r than t h e i r r a d i a i i imens ions {Cetermined by t h e subissembly p i t c h ) , thereby enabl ing ai- anta ape t o be cake?. of t h e f a c t C'

. . ~ n a t t h e hecerogenei:;~ of f a s t r e a c t o r s i s u s x a l l y m c n Less ir. the a x i a l . . . . . . d i r e c t i o n . This i s ic5 ieved bv , ~ ~ D L V : C S .. . b a zocz i 51.2~ ex3a11sion rh lc? , has zero tk order (2nd s e g r e e ) acccracy i n :he r a & i a l d i r e c t i o n s , k t i;l :'?e

. . - . axza i d i r e c t i o n , c a r have 2i:her z e r o : s t (?r? d e g r e e ) , or seccilC (4 th d e g r e e ) order a c w r a c y . F u r t h e r c o r e , i n the latter :wo c a s e s , zhe

. . ( a x i a l degendent) x a n s v e r s e leakage eppr3xiaa:ior. can 'se e - rnez f l a t or q u a d r a t i c .

. . T!x method cf selc:ion enployei iy :he 23Ce :s sased OF. 2 r e d ~ c z i c n cf . . . . - -

t h e nodal e?iiations L O a system cf equa:ions ;;:n a f i ? i r z c l r z e r e n c e ::<?e s t r u c t u r e , but which have c o e f f i c i e n t s iepencent cn c5e 2odai f l u x e s and i n t e r f a c e curre?.ts. These a r e s o l v e d u s i n g i convent ional f i s s i o n source i t e r a t i o n sc;?es?e ( 6 ) i n p a r a l l e l wi t ' . an ( c u t e r ) iterative update of t h e c o e f f i c i e n t s . The i c n e r i t e r a t i o n s a r e performed 5y :he l i n e Gauss-Seidcl method (6). Asyapto t ic e s t r a p o l a t i o n (7 ) i s used t o a c c e l e r a t e b o t h t h e outer and inner i t e r a t i o n s .

I n o r d e r t o a s s e s s and v a l i d a t e t h e code, c a l c u l a t i o n s were performed .- ~ Eor a 3D L M f B R benchmark ~ r o b l e m (8) (a 4 - ~ r o u ?

sodGm cooled 300 MWe f a s t r e a c t o r ) . I n t h e case of t h e f i n i t e d i f f e r e n c e code TIGAR ( 9 ) , t h e f a s t e s t c a l c u l a t i o n which produced a s o l u t i o n of s u f f i c i e n t ' accuracy f o r f a s t r e a c t o r a n a l y s i s ( v i z ke f f t o within C . 25%, power and damage r a t e d i s t r i b u t i o n s t o w i t h i n 4 % ) was made on a r a d i a l mesh of 6 t r i a n g l e s per subassembly ( 1 1 . 2 cm p i t c h ) and an a x i a l mesh of 36 p l a n e s . Comparable accuracy was obtained by : l E X X C on 2 r a d l a l a e s h of one hexagon per subassembly when: -

(i) t h e ze ro th o rde r method was used wi th 1 4 a x i a l p l a n e s ,

( i i ) t h e f i r s t o rder ( q u a d r a t i c : ransverse leakage) method was used w i t h 8 a x i a l p l a n e s , and

C i i i ) t h e second order ( q u a d r a t i c t r a n s v e r s e leakage) method was used w i t h 5 a x i a i ? l a n e s .

These c a l c u l a t i o n s r ep resen ted a r e d u c t i o n i n t h e number of nodes of a f a c t o r of 15 .4 , 27 and 36 r e s p e c t i v e l y , and r e s u l t e d i n a subsequent r e d u c t i o n , r e l a t i v e t o TIGAR, i n computing time of a f a c t o r of 11.6, 12.1 and 16.0.

These r e s u l t s c l e a r l y demonstrate t h a t t h e e f f i c i e n c y of HEmEC improves a s t h e number of a x i a l mesh p lanes i s reduced; even though t h e r e d u c t i o n must be accompanied by an i n c r e a s e i n t h e order of t h e nodal expansion. ' In more p r a c t i c a l f a s t r e a c t o r models though, t h e he te rogene i ty i n t h e a x i a l d i r e c t i o n w i l l be g r e a t e r than t h a t of t h e L I F E R benchmark problem. Often t h e presence of c o n t r o l r o d s i n s e r t e d t o d i f f e r e n t dep ths w i l l f o r c e t h e adopt ion of a r a t h e r f i n e mesh a t some l o c a t i o n s . To improve t h e e f f i c i e n c y oE t h e code on such problems, an ex tens ion i s t o be made which w i l l a l low a 2 i f f e r e n t order of nodal expansion t o be used i n each a x i a l mesh p lane .

Some work has continued on new methods of so lv ing t h e neu t ron t r a n s p o r t equat ion . This i s d iscussed i n a s e p a r a t e NEACRP pape r .

4 CRITICALITY WORK

Work has begun t o r e s t o r e t h e Winf r i th DINPLE water moderated ze ro power r e a c t o r t o i t s former ope ra t ing c o n d i t i o n . This work i s scheduled t o be complete b e f o r e t h e end of 1982, when a simple 3% enriched U02 p i n - l a t t i c e , i d e n t i c a l t o an e a r l i e r DIPPLE c o r e , w i l l be assembled. This w i l l p rov ide an oppor tun i ty f o r a s h o r t phys ic s commissioning programme and, i n p a r t i c u l a r , w i l l a l low a c o n p a ~ i s o n of t h e c u r r e n t f o i l t echn iqves , which

p l ay an important d i a g n o s t i c r o l e i n t h e planned c r i t i c a l i t y s t u d i e s , w i th those used i n t h e e a r l i e r experiments . k r k w i l l then begin on a s e r i e s of assembl ies of s to i :ape / t ranspor t a r r a y s of low enriched U02 w i t h f l u x - t r a p geometries. The a i n s of t h i s programme a r e twofold. F i r s t l y , t o provide a comprehensive v a l i d a t i o n of t h e methods i n c u r r e n t use f o r t h i s type of problem, i n p a r t i c u l a r f o r t h e BXFL CAGR s k i p and, secondly, t o develop techniques f o r monitoring t h e r e a c t i v i t y of t r a n s p o r t f l a s k s and s t o r a g e a r r a y s .

I n t h e t h e o r e t i c a l a r e a work has continued on the development of t h e rionte Carlo n e u t r o n i c s program MONK, which i s used widely i n c r i t i c a l i t y assessments f o r t h e f a b r i c a t i o n , p rocess ing , s t o r a g e and t r a n s p o r t of f u e l . Tne l a t e s t r e l e a s e , i n c o r p o r a t i n g a p o i n t energy t r ea tmen t , i s known a s MO3K6. MONK5 e x i s t s i n both p o i n t and group energy form. MONK6 u s e s a s u b s t a n t i a l l y improved nuc lea r d a t a b a s e , based on t h e IJKiiQL, and i n c o r p o r a t i n g some of t h e methods i n c u r r e n t use i n t h e thermal and f a s t r e a c t o r programs WIMS and PURAL. A t h e r m a l i s a t i o n t r ea tmen t f o r l i g h t water based on t h e Nelkin k e r n e l has a l s o been included i n order t o model molecular b ind ing e f f e c t s . S imi l a r t h e r m a l i s a t i o n models f o r heavy water and g r a p h i t e a r e planned. C a l c u l a t i o n s performed t o v a l i d a t e MONK6 a r e r e p o r t e d i n a s e p a r a t e LrEACRP paper .

5 USE OF FORTRAN-77 COIQILERS

Fortran-77 compilers a r e now avaj - lab le on t h e U M A mainframe computers (ICL, IEM and FRAY) and many U W A l o c a l mini-cozputers . The CEGB in tend t o acqu i re Fortran-77 compi lers f o r t h e i r mainframe.

The compi lers a r e be ing used on a t r i a l b a s i s i n t h e U W A w i t h a number of impor tant progi-ams, such a s PIONKG and PfURAL, i n order t o a s s e s s t h e problems l i k e l y t o a r i s e i n moving t o these new cou;pilers and i n confirming t o t h e Fortran-77 s t anda rd . A l l t h e compilers suppor t some ex tens ions t o t h e s t a n d a r d , some included d e l i b e r a t e l y , i n which case compile t ime warnings of non-standard use can sometimes be g iven , and some included a s a by-product of t h e implementat ion, when checks a r e more d i f f i c u l t .

The f u t c r e p o l i c y r ega rd ing Forrran-77 has not y e t been f u l l y d e c i d e d . It i s however l i k e l y tha: new p r o g r x s w i l l c o r I o m t o t i e s t anda r6 , whi?s: t h e development v e r s i o n s of e x i s t i n g programs will be changed t o conforrr. t o the s tandarc except when they a r e h e a v i l y dependec: on non-standard f e a t u r e s . Each progrm ir. t h e ia:ter ca tegory wocl l have t o be indivi+;al ly a s s e s s e d , one p o s s i b l e outcome being :hat the use of non-standard f e a r u r e s e v a i l a b l e i n e x i s t i n g Fortran-77 compilers would be a l l o w e l , p rov i i ed t h a t sui:able documentation i s provided .

Experience wi th t h e programs MONK 6 and ?KWL shows chat many of t h e non-standard f e a t u r e s i n t h e s e programs c m l d be removed r?Lth ve ry l i t t l e e f f o r t . The ioost Lmportant e x c e ~ t i o n s b e i n g ' t h e use of argument mismatch i n subrou t ine c a l l s and t h e u s e of t h e 'back-door e n t r y ' method of s i m l a t i n g Zynamic s t o r a g e a l l o c a t i o n . The former i s a v a i l a b l e a s an e x t e n s i o n t o t h e ICL compiler . Tine l a t t e r depends on t h e r e t e n t i o n of a s s o c i a t i o n between t h e arguments of a s u b r o u t i n e c a l l and t h e dummy argvments used i n t h e subrou t ine be ing c a l l e d . Although t h i s f e a t u r e of p rev ious compilers i s s p e c i f i c a l l y omit ted i n F o r t r a n 77 (ANSI X3.9 - 1978 FORTRAX 77 page 15-14 s e c t i o n 15.8.2 l i n e 35 ) , i t a l s o seems t o be p r e s e n t i n t h e ICL F o r t r a n i 7 compiler a s en ex tens ion .

0T31?iG C : (1982) "Aniiys?s of LOFT Zxperir?.e?.ts i n RZXkX-@ln Seconi I n r e r n a t i o n e l ZZTU.3 Meeticg, A p r i l 1982.

f o r Mulii-Dimensional ?.eaccor C i ? c u l a t i o n s " A:onkernenergie, Vol 30 , p (1 977) . WACHSPRESS E 5 " I t e r a t i v e S o l u t i o n of E l i i . s t i c Systems" D r e n t i c e H a l l I n c , Englewood C l i f f s , New J e r s e y (1 966).

WAGNER M R "GAUGE - A Two-Dimensional Few Group Neutron Dif fus ion-Deple t ion . Program f o r a Uniforx Tr i angu la r Mesh" GA-8307, Gulf General Atomic Company ( 1 968) . BUC'BL G , W T E R K and STEHLE 3 "3encPmark Calcul2tior.s f o r a Sodium Cooled Breeder Rezctor by Two and Three Diaens ional 3 i f u s i o n ?!ethods" Nucl Sc i Eng 701 64 75-89 (1977).

YATT'ZWS 2 D "UKAEA I n t e r n a l Docuqent" ( 1 968).

L'EGEND - CACTUS 0 GOG

X GOG GAP SMEAR

a GOG '13 CAN SMEAR

FIG. 1 GOG/CACTUS COMPARISON: 4 x 4 ARRAY CONTAINING 74 F U E L PINS AND 1 POISON PIN

F I G . 3 . Keff vs (20:. B l C E P AND BANFORD LATTICES

@ H A N F O R D

- -. -- - ,

UNITED STATES - 140 -

Reactor Physics Act iv i t i es i n the United S ta tes

A Report t o the NEACRP September 13-17, 1982

P. B . Hemmig and J . W . Lewellen U. S . Department of Energy Washington, D.C. 20545

Introduction

Recent reactor physics a c t i v i t i e s i n t he U.S. have supported the operation of '

FFTF, t he detai led design of CRBR, and preliminary design s tud ies f o r l a rger comnercial sized LMFBRs . Cri t ical experiments have been conducted usi ng the ANL ZPR-6 and ZPPR f a c i l i t i e s . The ZPR-6 diagnostic core program has provided valuable ins igh t into longstanding central worth and U-238 capture r a t e discrepancies. The ZPPR f a c i l i t y was used t o confirm the f ina l design and licensl'ng parameters f o r CRBR and i s now being used t o invest igate key physics issues of l a rger heterogeneous cores. The operational at-power t e s t i ng of FFT ? has provided a wl'de range of physics measurements. Generally these measurements confirm the adequacy of the methodology used for FFTF core and shielding design. Extensive measurements of the i r r ad i a t ion environment of FFTF have been completed f o r use i n FFTF fuels and materials t e s t programs. Calculations of selected FFTF physics benchmark parameters are i n progress t o assess recent improvements in data and methods and t o determine the appl icab i l i ty of FFTF experience to CRBR design and analyses.

Comprehensive assessments of LKFBR physics issues a r e underway a t ANL on the topics of control rod worths, sodium void reac t iu i ty , reac t ion r a t e d i s t r ibu t ions , c r i t i c a l i t y , Doppler r eac t iv i ty , and sample worths. Comprehensive l a rge core design s tudies have been continued by indus t r ia l and national laboratory organizations to evaluate various design a l t e rna t ives offer ing improved LMFBR economics, r e l i a b i l i t y and l i censab i l i t y .

Cri t ical Experiments

Experiments were completed i n October 1981 f o r t he ZPPR-11 s e r i e s of Enaineerinab Mockup Cr i t i ca l s (EMC) f o r CRBR. The f ina l s e r i e s of experiments i n the ZPPR-I1 se r i e s provided valuable confirmations of t he sodium void and Doppler r eac t iv i ty coef f ic ien ts expected for CRBR.

The ZPPR Assembly-12 program which began i n November 1981 u t i l i z e d a small 124 Kg f i s s i l e Pu core assembly with t h e CRBR un i t c e l l . Physics measurements of material worths used the long-drawer o s c i l l a t o r . Also included were f i s s ion and capture reaction-rate rrappings, gamma-heating measurements, and sodium-void mrth measurements.

Reaction r a t e s of 7-39pu ( n , f ) , 2 3 8 ~ ( n , f ) , 2 3 8 ~ (n,y) and 2 3 5 ~ ( n , f ) were measured with t h i n f o i l s i n one quadrant of t h e assembly. Gamma heating was a l so measured i n one quadrant u s i n g L i F themluminescent dosimeters (TLDs) . Heasurements of sodium worth were carried out i n axial s teps of 2 6, 2 12, and > 18 i n . fo r radial zones of 25, 36 and 60 drawers. After t h e core was compretely volded, t he configuration was loaded t o c r i t i c a l and reaction r a t e s were mapped w(th f o i l s I n one quadrant of the reactor.

Other measurements i n t h i s program were designed t o invest igate neutron streaming. One involved changing the drawer loading t o enhance neutron streaming. This ce l l arrangement was performed i n radial zones of 25, 36 and 60 drawers i n axial s teps of + 6 and - + 18 i n . Reaction r a t e s were measured i n the core w i t h a l l fuel drawers rearranged. The second neutron streaming experiment involved ro ta t ing the plates i n every other drawer by 900. The in t en t was t o eliminate, a s much as possible, t he radial neutron streaming paths. Reaction ra tes were measured i n t h e core w i t h rotated drawers. The f ina l ZPPR-12 measurements were made i n pin zones--a central zone and an edge zone. Reaction r a t e s were measured i n both zones and sodium

e. voiding measurements were made i n the central pin zone.

The ZPPR-13 se r i e s of the Jupi ter I1 program began i n June 1982 a s a cooperative program w i t h PNC, Japan. The program i s designed t o provide a systematic study of core neutronics for t h e design and analyses of l a rge heterogeneous cores. The f i r s t configuration consis ts of a simple, cyl indr ical core with a central blanket and three fuel r ings , each of which has a uniform thickness. The fuel rings a r e separated by continuous blanket rings also of uniform thickness. The f i r s t core volume i s approximately 4000 l i t e r s and has a c r i t i c a l mass of 2500 Kg plutonium.

A wide range of issues a r e being investigated i n t h i s program including the s e n s i t i v i t y of power d i s t r ibu t ion t o core blanket geometry; space and time response to r eac t iv i ty perturbations; control rod worths including rod in te rac t ions , and e f fec t s on power d i s t r ibu t ion ; and p red ic t ab i l i t y of c r i t i c a l i t y , sodium void and small sample worths. The program i s expected t o be completed i n approximately 20 months.

Experiments i n the Pu/C/SS diagnostics core (Assembly 10) were conducted during the f i r s t half of FY82. The measured parameters include control rod worths and ca l ib ra t ions , configuration reproducibi l i ty , gap worth, and temperature coef f ic ien ts . Uorths of small samples of materials Cincl uding enriched and depleted uranium (DUJ, Pu-239, carbon, SS, a1 uminum, and boron-10) were measured using t h e drawer o s c i l l a t o r and inverse kinet ics analysis .

Assembly 102, which was fonned by adding a 37 drawer zone of Pu/DU/C, was studied l a t e r i n FY82. Configuration r eac t iv i ty values were measured for a c r i t i c a l 21 drawer zone, .a subcr i t i ca l 21 drawer zone with e ight edge drawers removed, and a 37 drawer zone. The worth of each boron control lsafety rod was measured i n t h e reference configuration. The prompt temperature coef f ic ien t was measured and found t o be negative.

Reactor noise correla t ion techniques were used t o measure B/e, and t h e central neutron spectrum was measured w i t h proton recoil counters. The capture r a t e i n sodium was measured i n the central c e l l t o obtain a low-energy f lux t e s t of calculations. The central f i s s ion r a t e s of U-235 and Pu-239 were measured w i t h absolute counters for ca l ib ra t ion of f o i l measurements.

One i r rad ia t ion was made w i t h special depleted uranium plates i n the central u n i t ce l l t o determine the U-238 capture r a t e . Ultra-thin 0-238 deposits and Pu-239 f o i l s placed between the p la tes of the central un i t c e l l were i r rad ia ted t o measure capture and f i s s l o n respectively. U-235 fol 'ls were a l so exposed t o determine the U-235 f i ss ion r a t e w i t h i n t h e central un i t ce l l and radial and axtal d i s t r ibu t ions across the zone and dr iver regions of t he a s smbly . Subsequently, axial and radial d i s t r fbu t ions of depleted uranfum capture and f i s s ion were obtained with 0.5 and 1.0 mil f o i l s . These a r e for comparison w i t h r e s u l t s from the ul t ra - th in deposits .

The all-uranium, hard spectrum, diagnostic core measurements were completed i n July 1981. Generally good agreement was obtained between measured and calculated ' central spec t ra , par t icu la r ly when the calculat ions account f o r measurement hard- wa.re. Misprediction of t he peak energy i s the major unresolved discrepancy. Beta e f fec t ive was studied because the U-238 content was high. The measured r e su l t has an uncertainty of 1.3% and the C/E using ENDF/B, Version 5, i s within 1% of unity. Agreement when using other data s e t s i s s l i g h t l y l e s s favorable. Major r e su l t s of t he all-uranium core analyses wil l be given i n a paper by Bennett, ~chaefer.. and Di Ior io to be presented during the November 1982 ANS meeting.

Reactor Computations

Fuel Depletion

Advanced diffusion neutronics based on depletion codes which enable hexagonal-Z multigroup analyses a r e now being used i n the U.S. In recent t e s t calculat ions , the REBUS/DIF3D and BURNER/VENTURE-YALE systems showed very consis tent r e su l t s f o r major design parameters. The REBUS/DIF3D approach was a l so used t o prepare the U.S. contribution to the NEACRP burnup benchmark. This system has been tes ted on IBM and CDC computers and has been extended t o include a burn-cycle-time search. Effor t t o develop burnup capab i l i t i e s i s not l a rge and i s now concentrated upon achievement of computing economics by adding par t icu la r ly e f fec t ive special features , implementation of advanced methodologies for f lux solut ions , and by use of the most e f f i c i e n t computing hardware.

Kinetics

The FX2-TH code with two-dimensional dif fusion neutronics has been extended by adding a coolant boiling model. The overall t h e m h y d r a u l i c s model was refor- ' mulated concurrently to be f u l l y impl ic i t , an improvement which provides greater accuracy and pennits l a rge r time s t eps .

In addi t ion, theoret ical s tud ies have been performed t o assess t he potential of modal expansion methodology f o r characterizing the t r ans i en t behavior of LMFBR systems. Computational capabi l i ty t o ca lcu la te straightforwardly the higher harmonics of t he multidimensional, multigroup diffusion equations has been established. These harmonics can be used t o obtain a simple measure of local f lux t i l t i n g i n a given reac tor system.

Applications of Transport Theory

A two-dimensional, t r i angular mesh option has been added t o the DIF3D computations system developed by Argonne. Inclusion of gamna ray t ransport i n t he VIM Monte Carlo code has begun, and a Monte Carlo eigenvalue perturbation method has been developed which enables ser ious consideration of Monte Carlo for calculat ing material worths .

Ag isotopes and Rb isotopes, Pu-239, B-10, and natural elements f o r B , Kr, Ag, Eu, Xe. 6d, and Zr consistent w i t h i sotopic evaluations. Revisions of several covariance data f i l e s will a l so be included i n t he MOD I1 version. CSEUG benchmark t e s t i n g of ENDF/B-V has been completed. The r e s u l t s of t h i s t e s t i ng ind ica te substant ia l improvements over ENDF/B-IV for uranium fueled thermal reactors and l e s se r , but s ign i f ican t , tmprovements for f a s t reactor shfelding, f i s s ion product and dosimetry applications.

FFTF Physics

The various neutron f i e l d measurements i n t he FFTF character izat ion program were reported by J. Rawlins, e t a l , a t t h e ASTM-Euratom Symposium, March 22-26, 1982 [CONF-820321/VI). A high degree of consistency was obtained between re la ted measurements. I t appears t h a t t h e t e s t i ng program goals of 5-10% uncer ta int ies i n key integral parameters can be met by use of the calculational and measurement techniques developed i n t he Interlaboratory Reaction Rate (ILRR) and FFTF core character izat ion programs.

Gamma ray measurements were made i n t he F n F t o detennine the magnltude and spa t i a l d i s t r i bu t ion of t he gamma ray f i e l d . Energy deposition was measured using f i v e types of ion chambers, th ree types of calorimeters, thermolumescent dosimeters and self-powered gamma detectors . Preliminary evaluations indicated general agreement of measurements w i t h ca lculat ions w i t h i n 10% f o r the slowly varying f i e l d s . The more extreme f lux and heating gradients near control rod t i p s and some experimental assemblies a r e not a s well predicted.

Various benchmark calculat ions for i n i t i a l FFTF core configurations a r e i n progress using s ta te-of- the-ar t design methods and data . These benchmark s tud ies will be extended t o FFTF burnup data as these data become ava i lab le .

Shi el di n q

Measurements of radiat ion f i e l d s i n FFTF included mappings w i t h radioactivants i n t h e r e f l ec to r , i n vessel fuel s torage locat ions , and i n t he reac tor cavi'ty. Fluxes and dose r a t e s i n t he head compartment were surveyed w i t h bonner ball

0 detectors . The major shielding measurements took place during an eight day FFTF r u n a t 400 M W t . The r e su l t s not only provide d i r e c t character izat ions of in-plant radiat ion environments, but a l so wil l be compared w i t h shielding design predictions t o assess calculat ional accuracies.

Shielding design s tud ies of a 1000 M e plant concept have continued and have confirmed t h a t substant ia l weight and cos t savings can be real ized by carefu l ly choosing configurations and mi te r ia l s f o r t h e major in-vessel sh ie ld elements.

Core Design and Assessments

Assessments of t he state-of-the-art i n t h e prediction of key FBR physics parameters b v e continued a t ANL. The main conclusions t o date wil l be described i n a paper by M. Lineberry, e t a l , t o be given a t t he Kiamesha Lake meeting, September 1982. The m j o r s tud ies a r e of sodium void r e a c t i v i t y , c r i t i c a l i t y , U-238 capture, and small sample worths. Assessments of Doppler coef f ic ien ts and power d i s t r ibu t ions have begun.

A two dimensional d i s c r e t e ordinates code for analysis of hexagonal geometry i s being developed a t Los Alamos. Extended s tudies have shown t h a t t he l i nea r cha rac t e r i s t i c method of solut ion is s ign i f ican t ly more accurate on hexagonal meshes than the diamond o r weighted-diamond schemes. To ensure 60•‹ symnetry. there I s 60•‹ ro ta t iona l ly invar iant angular quadrature. A diffusion synthet ic accelerat ion scheme which requires fu l l consistency of t he t ranspor t and dif fusion synthet ic di f ference equations will be used. A modest development has shown t h a t a nodal technique can separate the ax ia l dimension from hexagonal planes. Thus, a three-dimensional d i s c r e t e ordinates code could be developed as an extension of the two-dimensional hexagonal code. This will be attempted , l a t e r i f near-term t e s t s i n two dimensions indicate su f f i c i en t computing speed.

Nodal Diffusion Methods

A nodal method fo r hexagonal and hexagonal-Z has been implemented i n the DIF3D system. Early use of t h i s method has shown some s ign i f i can t improvements over the conventional f in i te -d i f fe rence method. For a 3D, 1000 We sca le , eight- group t e s t problem, CPU time was about one f i f t h t h a t of t he corresponding

0 s i x t r i ang les per hex, mesh-centered f in i te -d i f fe rence calculat ion, and the accuracy was comparable t o t h a t of f in i te -d i f fe rence on a mesh of 24 t r i ang les per hex.

The DIF3D nodal option has been linked t o the REBUS-3 b u r n u p code, which can now obtain flux information from f i n i t e di f ference, synthesis , o r nodal ca lcu la t ions .

Independent research on nodal methods has been conducted a t Rensselaer Polytechnic I n s t i t u t e . This was reported in two June 1982 ANS papers, "Reflection-Based Interpolat ion i n Nodal Reactor Simulation" by Anaf and Becker, and "Hexagonal Geometry Fast Reactor Nodal Yodeling" by Caro and Becker. Development of methodology fo r hexagonal meshes has progressed through i n i t i a l t e s t s , where i t was demonstrated t h a t t he reflection-based coarse mesh method can be backfit i n to ex is t ing mesh-center di f fusion codes.

Data Processinq

The calculat ion of the spa t i a l se l f -shie lding fac tors in t he RABANL module of 0 M C ~ - ~ has been improved. New algorithms fo r computing transmission probabi l i t i es i n the CALHET co l l i s i on probabi l i ty module of SDX and i n RABANL have been imple- ' mented. U n i t c e l l fiomogenization calculat ions have been programmed t o use output of t he ONEDANT code.

A method of accounting f o r double heterogeneity a t t he s tage of data processing dealing w i t h composition, temperature and 1 umping has been included i n t he TDOWN code. This new fea ture enables consis tent and unified treatment of fuel pin sel f -shie lding on i ts pitch within t he fuel c lu s t e r , and of the duct s t e e l and sodium a t t he fuel element periphery. Calculations of se l f -shie lding i n two dimensional ZPPR c e l l s and of dr iver lblanket and driver/control element in teract ions a r e improved by appl icat ion of t h i s method.

Nuclear Data

Effor ts have continued t o improve the U.S. nuclear base fo r reac tor design repre- sented by t he ENDFIB-V l i b r a ry . A f i l e of updates and changes which has been designated ENDFIB-V MOD 2 will be completed by ear ly 1983. I t includes revisions of t he La, Fe, Th-232, and U-233 f i l e s , new evaluations f o r Li-7, W isotopes,

Applications of the F O R S S sensit ivi ty methodology have been carried out a t ORNL. In one example, a study of protected transients in F F T F gave predictions of the changes i n values and locations of maximum fuel temperature in the hot channel and maximum power level. These predictions agreed well with direct recalculations based on perturbed parameter values . Core analyses Rave continued in support of the 1000 Me LMFBR design studies. Fhjor issues addressed are design tradeoffs t o reduce plant costs and improve the plant performance rel iabil t ty and 1 icensability.

Reactor Phys i c s A c t i v i t i e s a t t h e J R C - I s p r a

Oct . 81 - S e p t . 82

Compiled f o r t h e 25 th NEACRP i n Kar l s ruhe , by H. R I E F

I. RADIATION SHIELDING

During t h e r e p o r t i n g p e r i o d a g a i n 2 g r e a t d e a l of t h e work h a s

been devoted t o t h e measurement and t h e i n t e r p r e t a t i o n of deep

p e n e t r a t i o n s h i e l d i n g benchmarks.

The measurements of t h e EURACOS I r o n benchmark may be completed

i n Summer 8 2 . Ref ined s t a t i s t i c a l p rocedures were deve loped t o i n -

t e r p r e t e t h e a c t i v a t i o n d e t e c t o r measurements c o v e r i n g l a r g e a t -

t e n u a t i o n f a c t o r s ( e .g . : i n t h e c a s e of S32(n,p)P32 measur-

ements) and t o c a l i b r a t e t h e s o u r c e s t r e n g t h [l, 2, 34.

P a r a l l e l t o t h i s a c t i o n a sodium benchmark, r e a c h i n g 400 cm

p e n e t r a t i o n dep th ,has been c o n s t r u c t e d . I n a major e f f o r t 1 0 t o n s , of sodium were, under vacuum, pu t i n t o seven s t e e l boxes o f appro-

x ima te ly 200 x 150 cm c r o s s s e c t i o n . They a r e f u r n i s h e d w i t h r een -

t r a n t h o l e s which w i l l accomnodate t h e a c t i v a t i o n o r p r o t o n r e c o i l

d e t e c t o r s .

A more d e t a i l e d r ev i ew o f t h e s t a t e o f t h e a r t o f t h e EURACOS

i r o n and sodium benchmark i s c o n t a i n e d i n [ 4 ] .

The i n t e r p r e t a t i o n of bo th - t h e ASPIS and t h e EURACOS i r o n benchmarks l e d t o a s e r i e s of unexpected compl ica t ions , such as t h e need f o r buck l ing e s t i m a t i o n and c r o s s s e c t i o n weight- i n g as a f u n c t i o n of t h e d i s t a n c e from t h e s0urce.A f i r s t account of t h e adjustment s t u d i e s u s i n g t h e code ADJUST-EUR i n c o n j u n c t i o n

, wi th RSYST was p resen ted a t t h e Antwerp meeting on Nuclear Data i n

Sep t . 82 .

For qu ick , bu t r e l i a b l e e v a l u a t i o n s of gamma s h i e l d s a number of easy t o handle approximat ion formulas were compiled and publ i shed i n e popu la r t e c h n i c a l n o t e , e n t i t l e d "Gamma S h i e l d i n g Es t ima tes on t h e back o f a n Envelope" 153.

A s p a r t of 3D Monte Car lo method development a new low va r i ance p o i n t e s t i m a t o r based on l i n e of s i g h t t r a c k i n t e g r a t i o n was developed. It was incorpora t ed i n t o t h e TIMOC code where

i t i s a l s o used f o r p o i n t f l u x s e n s i t i v i t y a n a l y s i s [ 7 , 81.

Th i s new f e a t u r e , t o g e t h e r w i t h d i r e c t i o n dependent e x p o n e n t i a l t r a c k b i a s i n g has been a p p l i e d t o a " f i e 1 d " t e s t c a l c u l a t i n g n e u t r o n dose r a t e s a t d i f f e r e n t p o i n t s o u t s i d e t h e s a c r i f i c i a l s h i e l d of a PWR. I n p a r t i c u l a r neu t ron s t reaming through t h e a n n u l a r gaps around t h e p r e s s u r e t u b e s was ana lysed and compared t o Au and N i f o i l a c t i v a t i o n measurement.

I n c o l l a b o r a t i o n wi th t h e Rad ia t ion P r o t e c t i o n group o f CERN-

Geneva t h e neu t ron dose r a t e i n a s p e c i f i c expe r imen ta l a r e a , which i s one of s i x similar a c c e s s ways t o t h e underground r i n g t u n n e l , was ana lysed i n d e t a i l by Monte Car lo and compared w i t h semi-empirical formulae.

For f u s i o n r e a c t o r b l a n k e t / s h i e l d s t u d i e s a 48-group (P3) coupled

neut ron gamma (34-n-14g) c r o s s s e c t i o n l i b r a r y was gene ra t ed f o r t y p i c a l m a t e r i a l s and weight ing s p e c t r a 191.

The code ATTIVO-11, a f u r t h e r development o f ATTIV0,was completed.

A s we l l as a c t i v a t i o n , a f t e r h e a t and garma d e n s i t i e s i t c a l c u l a t e s

by a more g e n e r a l mathemat ica l a l g o r i t h m t h e changes i n t h e mate-

r ia l composi t ion of i r r a d i a t e d m a t e r i z l s [ l o ] .

Repor t s and P u b l i c a t i o n s

[l]' "The EURACOS A c t i v a t i o n Exper iments : P r e l i m i n a r y U n c e r t a i n t y

Ana lys i s " , Y . Yeivin , EUR 8011 EN, 1982

121 "The Unfolding Counting-Rate S p e c t r a of Recoi l -Pro ton

Neutron D e t e c t o r s " , Y . Ye iv in , EUR Zepor t t o be p u b l i s h e d ,

1982

133 "The EURACOS Source C a l i b r a t i o n " , W . Mat thes , p r i v a t e commu-

n i c a t i o n , 1982

[ 4 ] " I n t e g r 8 1 S h i e l d i n g B e n ~ ~ ~ a r k s " S t a t u s of t h e EUIiACOS I r o n

& Sodium Deep P e n e t r a t i o n E x p e r i n e n t s " , H. R i e f ; P roc . o f

t h e R e s t r i c t e d S p e c i a l i s t Meeting on S h i e l d i n g Benchmarks,

OECD-Paris, J u l y 1982

[5] "Gamma S h i e l d i n g E s t i m a t e s on t h e Back of a n Envolope", 0

H. Penkuhn; ESIS-Newsletter No 38 & 39, Ju ly /October 1981

C61 "A Proposa l f o r Approximations o f t h e Gamma Ray Bui ldup

F a c t o r s i n Two-Layer S h i e l d s " , "Gamma-Ray Eui ldup F a c t o r s

f o r 0,66 MeV Source Energy i n Al-Pb and i'b-A1 S l a b S h i e l d s "

and "Energy Dependence from 0 ,5 t o 4 MeV o f a F i t t i n g Equa-

t i o n f o r Gamma-Ray Euild-up F a c t o r s i n a S p e c i a l Two-Slab

Sh ie ld" , H . Penkuhn, ESIS-Newsletter No 4 1 & 42, 1982

173 "Track Length Es t ima t ion Appl ied t o Po in t D e t e c t o r s " ,

A . Dub1 & H . R i e f , a ccep ted f o r p u b l i c a t i o n i n NSE

[8] "On Confidence L i m i t s and S t a t i s t i c a l Convergence o f

Monte Ca r lo P o i n t F lux E s t i m a t o r s w i t h Unbounded Var iance" ,

A . Dubi, T. E l p e r i n and H. R i e f . a ccep ted f o r p u b l i c a t i o n

i n Annals of Nucl. Energy

[g] Program ATTIVO-I1 - A code f o r c a l c u l a t i n g a c t i v a t i o n ,

0 decay-heat and i s o t o p e - t r a n s m u t a t i o n i n f u s i o n r e a c t o r s ( i n

I t a l i a n ) ; A.Care t ta , L . G i a n c a r l i - Techn ica l Note

No 1.05.07.81.172

[ l o ] "SHAMSI-48 Group Cross -Sec t ion L i b r a r y f o r Fus ion Nucleonics

Ana lys i s " , EUR 7798e, 1982

11. CORE PEYSICS STUDIES

I n t h e p l ann ing o f l o s s o f c o o l a n t exper iments t y p i c a l o f LhrRs,

known as t h e J R C ' s SuperSara program, a s e r i e s of r e a c t o r p h y s i c s

s t u d i e s a r e under way. They d e a l w i t h a l i g h t wa te r t e s t l o o p ,

c o n t a i n i n g 32 f u e l p i n s , i n s e r t e d i n t o a heavy water environment

(ESSOR-reactor)fed by f u l l y e n r i c h e d U235 f u e l e l e m e n t s .

The s t u d i e s d e a l main ly wi th : . a ) o p t i m i z a t i o n o f t h e U235 enr ichment i n t h e t e s t l o o p , s o

t h a t a f l a t power d i s t r i b u t i o n i s ach ieved

b ) d e t e r m i n a t i o n o f t h e ( p o s i t i v e ) vo id e f f e c t d u r i n g blow

down

c ) f i s s i o n produc t d i s t r i b u t i o n and gamma and b e t a h e a t i n g

e f f e c t s a f t e r r e a c t o r s h u t down

d ) r e a c t i v i t y c a l c u l a t i o n s f o r f u e l s t o r a g e and h a n d l i n g

e ) a d a p t a t i o n o f a 3D space dynamics d i f f u s i o n code SYNTX-C

t o t h e SuperSara d e s i g n r e q u i r e m e n t s

f ) performance and i n t e r p r e t a t i o n o f mock-up expe r imen t s r e g a r d - i

i n g power d i s t r i b u t i o n s and vo id e f f e c t s .

Repor t s and P u b l i c a t i o n s

[ll] "Thr+edimensional Ana lys i s o f SuperSara Tes t C h a n n e 1 . b

t h e ESSOR Reac tor by KIM-E3D" ( i n I t e l i a n ) , R.Ricchena,

M.Agliet t i-Zanon, Techn ica l Note X0 1 .06 . i9 .82 .40 ,Apr i l 5 2

[12] "Nuclear c r i t i c a l i t y s a f e t y e v a l u a t i o n f o r SUPER SARA

KOCK-UP ASSEMBLY" , Tayyab Abbas, Con t r ac t TEAM/EURATO?I

No 1668.81.12 ED ISP I

[13] " V e r i f i c a t i o n o f S u b c r i t i c a l i t y of t h e C o n t a i n e r s Tran-

s p o r t i n g t h e SuperSara Mock-up F u e l Rods ( i n I t a l i a n ) ,

R . Ricchena, EUR Repor t , 1982 - t o be p u b l i s h e d 0 1141 "LIBSS - A c r o s s s e c t i o n l i b r a r y f o r SuperSara n e u t r o n i c ,

c a l c u l a t i o n s " , E. C a g l i o t i , R . Ricchena, Techn ica l Note

No 1.06.19.82.91, J u l y 1982 . [15] "Determinat ion of Enr ichments f o r t h e SuperSara T e s t

Bundle i n a S t e e l P r e s s u r e Tube" ( i n I t a l i a n ) , R.Ricchena,

EUR Report , 1982 - t o be p u b l i s h e d

[I61 " S e t t i n g up and v a l i d a t i o n o f t h e VENTURE-2 Program".

M.Agliet t i-Zanon, Tayyab Abbas , Con t r ac t TEAM/EURATOM

No 1828-82-03-ED ISP I

Annex USSR

RWISW OF ACTFJITIES ON FIST REhCTOE PHYSICS

YU= A. ~ e z a m k y , U.P. *oyenov, . A . moderev

hbstrac t

The repor t g ives a review of ac t iv i tLes on fast r eac to r > physics c e r i e d out in 1980-1982. The maMattent ion is given

t o experimeilt&l . lvest igetions. c a r r i e d out at. power r e a c t o r s . .

and c r i t i c a l f a c i l i t i e s .

In t roduct ion . . .

m o m t i o n on fast r e a c t o r physics & c t i y i t i e s from

January 1980 till June 1982 was included in the review. A t tkat period the work oa overher ling and improveinert

of s epc re t e systems of t h e BR-7 0 reac tor . was' c ' e i e d oet. T E ~

BOB-60 r e a c t o r w a s success fu l ly operat ing in t h e RTP (Buclear FowerP lan t ) regime, i ts t h e m 1 power be& regulc=ef~ by

t he i r r a d i a t i o n condi t ions of en experiment& ((fuel and t e s t % a t e r i a l ) asse;nblies.The therinal power reached 50 LT. The 35-350 r e a c t o r operated at s teady-s ta te operating conl?iticr.s

wi th t h e e v a i l e b i l i t y f a c t c r 6.9. In 1980 i t s -thermal power

was 650 ( o r 125 LITe and 80 000 t of d i & t i l l e d n e t e r per d q ) . 1981 t h e poxer was increased up t o 700 WJt. 'In t h i s case

t h e e l e c t r i c power mas increased up t o . 140 W;e a t the s m e

l e v e l of d i s t i l l e d water production. Ln 1980the B3-35C . reac tor core replaceineot by f u e l p ins of l a r g e r diameter

lvss completed. It w a s done t o reduce t h e cost . of fabr icp t2oa a d . m i f i c a t i o n with the ' BN-600 f u e l pi[os. A d i ene t e r . of t he new f u e i eleinent i s 6.5 mm, t h e cladding t h i c k n e s s i s 0.4 m.

In 1980 assembling and precomissioning works a t t'ce 3X-600 r e a c t o r were completed, ini t ial c r i t i c a l i t y vras eckiei-€6 on 26 February 1980, and on 8 Apri l 1980 t h e r e a c t o r reecketi

30% power leve l . According t o 'ihe sched.de of Dover increese 5.a ~ b v e = n e r 1980 t h e r e a c t o r =as at the 6% p o w r l e ~ e l , i ?~

[IT] "Adaptation of the SYNTH-C program to the specific problems of the LB and SFD tests simulation", E. Salina, Contract ARS/EURATOM No 1667-81-12 ED ISP I

[18] "Nuclear criticality analysis for the storage of the c

SuperSara MOCK-UP fuel rods In the ESSOR pooln(TEAM/EURATOM),

M. Aglietti-Zanon, Tayyab Abbas, EUR Report to be published

[lg] "Use of the Program GRANT-3 for the Generation of Two Group Cross Sections Applied in SYNTH-C" (in Italian), R. Xicchena,

a EUR Report to be published

2,. Iovestigetioz of Xeutronic ~ &aracteristics of the 3X-600 Beector

tne.B%600 reectc-r 10% ?ewer 3nys:cs t e s t s a d b t e r p r e k ~ i o o s of the z e s u l t s k v e been aescrijeC is a spec ia l e p e r p e s e z t e 6

.. .

t o t he meetbg. Sere we s h e l l only point out , t h a t t he deviat ions observed between design an6 ac tua l c h a r a c t e r i s t i c s

d i a not requi re any r a d i c a l changes io loading the r eac to r or i t s design. Thus, f o r exanqle, t he measui-ed e f f i c i ency of e ccn t ro i rods system ( j , S 6 2 0,10)% A kk/i coincid.es w i t h i n

2% viith t h e design one i5.,73% A k/k). The .measrired e f f i c i ency

of t h e s a f e t y rods appeared t o .be ('3,.2 t 0,23$5 4 k/k, -thet . ,

is below t h e design one by 20%. ow ever t h e a c t u a l e 'fficiency .

'

s a t i s f i e s nNuclear Sa te ty Gides" and guarantees :normal

operation of t he reac tor . The init ial c r L t i c a l i t y load5ng dirfferes froin t h e design one by 1,5% ak/k, w i t h t h e . ac tue l

s t a t e having a l a g e r excess of reactiVil;g,. There a r e d i f fe rences reaching 20% between t h e 'measured and ca l cu l a t ed temperaiz&e

and power r e a c t i v i t y e f fec t s . The r a t e of r e a c t i v i t y l o s s coincided v r i t h i ~ 7% vrith t h e desii;n value (measured value 3,21 2 o,o~#/E.D.B.P (Equivalent days at full power) end d e s i g i value - ~,o{/E.D.P.P.). Eower deos i ty 6 i s t r i b u t i o n in t h e ini t ial loa3ing dif ' fered from t h e design one anly f o r per iphera i f u e l sub-assemblies, which a r e at t h e boundary with t h e blanket ( t h e ca l cu l a t i ons underezt inate power densi ty by - ID;;).

After b r h g i n g t h e r e a c t o r t o t h e equil ibrium condi t ion a l o t of neutronic c h a a c t e r i s t i c s heve been remeasured,.such

as the e f f i c i ency of con t ro l and s a f e t y rods, power d i s t r i b u -

t i o n s , power e f f e c t of r e a c t i v i t y , etc..

3 . Inves t iga t ion of &el Cnerac t e r i s t i c s a t t h e Bn-350 Reactor.

I

!L'he ana lys i s of i r r a d i a t e d f u e l and' specimens - n i tnes ses by t h e gravichemical, ra3iochemical and mass-spectroneter

methods i s being continued. "Qui te r ecen t ly t he f i n a l r e s u l t s "

on cross-sections r a t i o s f o r f u e l nucl ides have been obteided. These r e s u l t s heve been coinpared with t he neasurezents by

a c t i v a t i o n methods. To heve en idea of e r r o r s and dev ia t ions

of measured and ce l cu l e t ed velues, t a b l e one gives r a t i o s of

Z I - ~ - * E ~ E . cross-se-z5ons a d :he c c - z ~ s p c ~ ? ~ c.Scnlezec 2 2 ~ 8 (& k h ~ ~ c l i ~ i 3 ) f o r e 10vi-e~icI-zert Tone of ;he 33-350 r a a c t a r .

n i t i l b ?$,the measured value e r r o r vies 70%. The use of BNAB-78 h'uclear Date a d z l so & de fe i l ea

descr ip t ion of nucl ide concentre t ion dis%ri-Dution during r e a c t o r operation gave a ce lcu la ted value (0,45% b k/k/ month ) of t h e r e a c t i v i t y l o s s at t h e expense of f u e l b u m p

agreeing, wi th t he meesuzed one (0,46 2 0,03% ~kfk/month) .

Uore de t a i l ed d a t a on t h e . r e s u l t s of -the BN-350 r e a c t a r

physics i nves t iga t ion are in phpers / 1 / ., / 2 / . . ~

4. Inves t iga t ions a t C r i t i c e l Assemblies. . .

Early in 1981 t h e work on s i m l a t i n g a c e n t r z l a r e a of t h e BE-800. r e a c t o r wi th plutonium lo&w (BFS-44 asseubly) was completed st the BFS-2 f a c i l i t y . A+, this model a breeding

r a t i 0 , r e a c t i v i t y e f f e c t s determining r e a c t o r s a f e ty - sod im voiding e f f e c t of r e a c t i v i t y , r e a c t i v i t y e f f e c t s occurring et core subassemblies des t ruc t ion esld at t h e e n t r y of

hydrogen were measured. - T i e l o c e l breeding r a t i o meesured in t h e cen t r e of the

core eppeered t o be 0,832 5 0,025. The s imi l a r ca lcu la ted

value vihen us ing t h e BNAB-78 Xuclear Date was 0,8115, t h a t i s

in agreement viith t h e experiment. Calculat ions, as i n the cases of urenium models of fast

r eac to r s , p r ed i c t t h e sodium voiding r e a c t i v i t y e f f e c t t o be

more p0sitiv.e . The r a t i o s of t h e ca lcu la ted e f f e c t s t o '; bne measured ones a r e wi th in 1,15 + 1,20.

S W e t i o n of essemblies mel t ing w a s c a r r i e d out as f o r

t he uraniun model of t h e r e a c t o r / 3/. In t h e plutoniuoL nodel

as one should expect t h e r e appeas more p o s i t i v e e f f e c t s c f r e a c t i v i t y , which can be pred ic ted by t h e eng*eerirg calcul5-

t i o n with an e r r o r 20%.

In 1981 et t h e BFS-2 f a c i l i t y e broad progren on studyix;r.5 heterogeneous conposi t ion of t h e pomer r e a c t o r core us ing me te l l i c uania~ i n t h e breeding zones mas s t a r t ed . The . ,

33'3-46 c r i t i c e l assembly has two incer breeding zones ( c e n t r e l

and annannJ1er). Fuel zones cont = in ma te r i e l s - h u l e t i n g Pu02-DO2 10adb.g. For reaching c r i t i c a l i t y t he re is a zone

r- - racle 2.

of r e a l f u e l assemblies of t h e BK-600 r eac to r , piacec ic tke cen t re of t he core, ill be coinp=ed. Secondary, it i s schednled t o s tudy i n t e ~ d c h a r a c t e r i s t i c s bg p iac ing var ious

compositions - 1 5 cm i n diameter io t he cen t re of -' bne zone imetelic depleted urmiurn dioxide) t o check the p o s s i b i l i t y

of d e s c r i b k g process li'mbers, cross-sections r a t i o s etc. in heterogeneous compositions by t he ava i lab le ca l cu l a t i on

progrmmes. -4t t he KOBRA f a c i l i t y in 1980 a programme of s tud ie s

on a model of a heiium-cooled fast r e a c t o r . (BGR-300) was . completed. In the whole we pointed ~ u t a s a t i s f a c t o r y ag-ee-

m a t between the ce lcu la ted and experimental data. Thus, f o r ' example, ca l cu l a t i on by the l~honte-car& method i n the .26- &oup approximetion gave the value of K e f f by 0.5% more than the experimental value. The d e t a i l e d r e s u l t s of i nves t i -

gat ions e r e given i n peper 1 4 . In 1981 a t the YS3-9 c r i t i c a l assembly an insert icxi

with K,=l cons i s t ing of Pe znd h ior ide of enriched uraim mas studied. This assembly i s assembled t o ob tabL more represen ta t ive i n t e g r s l c h a r a c t e r i c t i c s f o r Fe. Ln XBR-9 t h e v n l m e of i n s e r t i o n i s 8 t i a e s t h a t of t he WR-3 asse-,Sljr

i nden t i ca l t o i t by conposition. it made i t poss ib le t o minimize e r r o r s generated by leekege of neutrons and t o i nves t iga t e t he dependence of t h e r eac to r ~ t e g . e l charzcte- r i s t i c s (x+ e t a l l on the i n s e r t i o n volune. I n t he K32-9 assembly, r e a c t i v i t y c o e f f i c i e n t s l o r e number of s t r u c t w a l mater ia l s were invest igated.

In 1981-82 long-term p s o p m e s of studying neutron spec t r a / 5 1 and conversion r e t i o s / 6 / were su-med-up. h

a i

p a r t i c u l a r it i s po-hted out , that the difference be txeer t he exper iaen ta l and ce lcu le ted spec t r e i n t he e n e r a rage

1 0 Kev + 1 Uev f o r a l l a s senb l i e s i s i ~ i t h i n t he double e r r o r

of t he experiment. In the energy r a w e above 10 Kev end sboxe I Liev f o r some conpo,sitions t he d i f fe rence tiiree-loii-

t i n e s exceeds t h e e x p e r h e n t e l er ror . Being evelucted over

. . . 3 2 Xeeactor 3 e m . ,

. . .Xeesu--ene?lts o f t r ~ z L s s i o n f . m c ; ~ c s usiry ve--Lo-= ' - r ecor6 i rg detectcrs ere sys temet i cd ly C V T > P ~ out et t i e . . ~ . .

r e c t o r be= by the time-of -f li&t method. W s = a l e s us. to . o b t a b s o ~ p factors of resonznce seE-shie ldkg o f

o t a l cross-section, ~ S s s i o n cross-section md rzdie t ion a p b e . c r o s s - s e c t i o ~ Qter tLe e d e p a t e treatmeat 3f dzt?te. e r e d t o r t he . - h ~ e s t i g a t i o c s the f ectors of r e s o w c e

' ~ $ 2 - s s e i d i o g o f t o t d cross-sec%ions For 2 3 6 !Jj 239% 9

2 3 5 ~ m d d s o af f i s s ion . cz-oss-secticns f c r . 235u I 239pa xere x e e s n e a / 7 / . Thus, f o r a w p i e , the factors o f

r e s o n a c e se l f - sh ie ld ing of t o t a l cross-sections 2nd - . i l s s i o n cross-sections f o r 2 3 9 ~ were measwed 5n ' the energy range 5 ev + 21 Kev, t h a t i s f o r i I + 2 < groups of t he BNkB nuclem de ta system. Yne e r r o r of measuring the f ac tors of

resonmce s k i e i 6 b g depends on the enera- region and i s in the range 3 + 1%.

6. Calculat ion- Theoret ical S tua ies on Development of ~ a l c u l a t i o n Nethods

A neu ml t i -g roup system of t h e BRAB-78 nucleafc de t a described in d e t e i l 21 1981 i n study / 8 / carte i n t o operation.

The nev; vers ion of group constants provides t h e unse r t a in ty dm-hg ca l cu l a t i ons of t h e Bi2 and Keff of -UDBR equal t o 2,3% and 1,4%, respect ively . from t h e ane lys i s one can concluce, t'net in t n e BNAB-78 n-dclem d a t a system capture cross-

s ec t ions of s t r u c t u r e l o a t e r i e l s , f i s s i o n products, cross- sec t ions of i n e l a s t i c s c a t t e r i n g of s t e e l m d xm.nil;m nee2 correct ioz . M t e r t h i s we shell be eb le t o perform &gori t&

f i t t i z g ig& t o s e t i s f , y t h e required eccu^-acy i n group cross- sect ions .

Nowadays or. t he b a s i s of B H B - 7 8 i-iith t h e use of t h e

ARLLUXO p r o p m k , mcroscopic constants f o r ca l cu l a t i ng

neutronic c h a a c t e r i s t i c s of t h e r e a c t o r and i t s s'hieldhi& can be prepere&+ BNB-78 Nuclear Data a se a l s o used ' f o r calcu- l a t i o n s by sub-goup zpproxim&tion. I n p e r t i c u l z r , t'ne sub- group approximation 732s r e a l i z e d in calcu1ation~progren:ies employing t h e Uonte - Carlo method ssd the method 02 c o l l i s i o s

probebi l i ty . These programnes, f o r exmqle , enzble us t o a

)

evaluate experiments c a r r i e d out et fest c r i t i c e l assenbl iec . Theoret ica1, invest igat ions of t n e a r e a of app l i ca t ioa of t h e

group approximetion were c m i e d 0 7 ~ t . Tie rzin conclusioc i s

t h a t t h e e r r o r i s due t o t he methodicei s i d e of preparing e l a s t i c slowing-durn cross-sections.

Oiving t o t h i s uncer ta in ty t'ne e-rrcr Keff mjr be 0 ,5 - 1.0% a d in 32 - 1%.

The stuciies on developing t7:o-ciaersionei a d t.hree-

&esi o n e zxg-m>e- . 502 en_gbeerkLg c e l c d z t b o c s

2 c e 0 . &e of tfis grogpzzces - X.3-a - i s -3-

dinewo?;&L, i t s t - o p r e t i n g , lovi-goes ( ~ p t o 6 go i ip s ) i z t 5e -

'1- di f fus ion eprox-tion. 1;1 t-ds progzmiae hexegonzl ger++trj- is -asec.

:. . . : A low-coup t'mee-dimensionel progrer;lie TFLGEX cane . .

. ' into t e s t . o ? e r e t i o r . TnLs progeeme i s nz3e i n t h e d i f fu s ion . .

. . a p ~ r o x ~ d t ~ o n . A peck of ~ r o , ~ ~ e s R9X-80 T i e s put h t o t e s t . operztion. -%es'e 2 r o m e s z r e intended f o r ce l cu l e t i on

of _3lysicel, hy6ra-dic a& econorLc ind ices of t he fest r e a c t o r core a d =e. used f o r c e l c d a t i o n of t he prospect- na tx re

f2yoirlib L.L., Zvonarev B.V., Ivznov 8.17. e t el.

"Calculs t ionsl ank b p e r i m e p t a l Lnvestigations of 3N-355 Reactor Physics C h ~ ~ a c t e r i s t i c s " . Report SN-225/62

a t symposium i n Bologne, April 7978, p, 263,'

Bnisimov V.I., Gonchzrcv B;K., Zvolla-ev A.V. e t al. "Ceiculat ional and Experben-cal Inves?;igations o f 3N-35C Eeaczar Physics Cia-acterist ics". Report at Soviet-

3rench S e e m , Obninsk, Deceeber 1980.

Belov S.Y. e t al. uReactivizg Ef fec t s in h e 1 Bet king S W a t i o n n . Repor;

I B B S'i - 244/80 et Symposiur on Past Reactor B y s i c s

0 i n 4ix-en-Provence, Septerrbei-, 1979 !v. 1, p. 345).

Poxomrev-St epnog E.X., Pzotsenko A,??, et al. --

5.xwest5.gation of Xeutronic C h a a c t e r i s t i c s of z e i i m C ~ o l e c Past Breeder Resc-;or BRG-300". Toprosy Atomoy

Nauky i TakbnLxy. Ser. -sic8 i Tec'knika JederniKi

Reektorov, v . 5 ( 1 8 ) , Eosk?ra iKCKIET, 1981, p. 2 ; .

EzzansLy Yu. A , , Vanlkov A.L., Voropaev X.I. e t a l .

llStuciy 05 neutron s p e c t r a et 3FS a s smnl i e s " . A t o m e p

Znergiye, 1982, v. 52, N 4, p. 235.

Kazaosky %.A,, D u i a V.A. e-l el.

nS+ady c f c s n ~ e r s i o n peemetars a; BFS fest c r i t i c e l assemblies" Atomaye a e r g i y a , 1952, v. 52, F 3, p. 233.

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