Hindawi Publishing CorporationScience and Technology of Nuclear InstallationsVolume 2012, Article ID 173637, 19 pagesdoi:10.1155/2012/173637
Research Article
SPES3 Facility RELAP5 Sensitivity Analyses onthe Containment System for Design Review
Andrea Achilli,1 Cinzia Congiu,1 Roberta Ferri,1 Fosco Bianchi,2 Paride Meloni,2
Davor Grgic,3 and Milorad Dzodzo4
1 SIET S.p.A., UdP, Via Nino Bixio 27/c, 29121 Piacenza, Italy2 ENEA, UTFISSM, Via Martiri di Monte Sole 4, 40129 Bologna, Italy3 FER, University of Zagreb, Unska 3, 10000 Zagreb, Croatia4 Research and Technology Unit, Westinghouse Electric Company LLC, Cranberry Township, PA 16066, USA
Correspondence should be addressed to Roberta Ferri, [email protected]
Received 11 March 2011; Accepted 27 July 2011
Academic Editor: Alessandro Del Nevo
Copyright © 2012 Andrea Achilli et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
An Italian MSE R&D programme on Nuclear Fission is funding, through ENEA, the design and testing of SPES3 facility at SIET,for IRIS reactor simulation. IRIS is a modular, medium size, advanced, integral PWR, developed by an international consortiumof utilities, industries, research centres and universities. SPES3 simulates the primary, secondary and containment systems of IRIS,with 1:100 volume scale, full elevation and prototypical thermal-hydraulic conditions. The RELAP5 code was extensively used insupport to the design of the facility to identify criticalities and weak points in the reactor simulation. FER, at Zagreb University,performed the IRIS reactor analyses with the RELAP5 and GOTHIC coupled codes. The comparison between IRIS and SPES3simulation results led to a simulation-design feedback process with step-by-step modifications of the facility design, up to the finalconfiguration. For this, a series of sensitivity cases was run to investigate specific aspects affecting the trend of the main parametersof the plant, as the containment pressure and EHRS removed power, to limit fuel clad temperature excursions during accidentaltransients. This paper summarizes the sensitivity analyses on the containment system that allowed to review the SPES3 facilitydesign and confirm its capability to appropriately simulate the IRIS plant.
1. Introduction
The IRIS reactor, with its integral design, is an advancedengineering solution of the latest LWR technology. Medium-sized, safe, modular, and economic, it provides a viablebridge to generation IV and satisfies the GNEP requirementsfor grid-appropriate NPPs [1–3].
In the frame of an R&D program on nuclear fission,funded by the Italian Ministry of Economic Development,ENEA, as member of the IRIS consortium, is supporting thedesign, construction, and testing of the SPES3 ITF at SIETlaboratories [4–6].
The SPES3 design was carried out following the subse-quent steps: (a) definition of a preliminary facility design,based on specified system geometry; (b) setup of theRELAP5 facility model and DBA simulation; (c) comparisonof SPES3 and IRIS results against the same transient;
(d) identification of the main differences and understandingof related reasons; (e) FSA application to selected thermo-fluid-dynamic parameters in order to assess and quantify thediscrepancies; (f) updating of the SPES3 design to matchthe IRIS behaviour; (g) final result comparison; (h) finalFSA application and assessment of acceptability criteria forconsidering SPES3 correctly simulating IRIS.
The above-mentioned process allowed to verify theSBLOCA PIRT objectives for the IRIS reactor, as defined bya group of international experts [7]. The Phenomena Iden-tification and Ranking Table put in evidence the thermal-hydraulic phenomena playing an important role in operationof IRIS safety systems. Two figures of merit were consideredfundamental for the accident sequence control: containmentpressure and reactor vessel mass inventory. Sufficient waterin the vessel allows to remove stored energy, and decay heatwithout fuel clad temperature excursions and adequate heat
2 Science and Technology of Nuclear Installations
SGs
Pump
PRZ
CRDM
Core
FL nozzles
SL nozzles
DCRPV
LP
Figure 1: IRIS integral layout.
Figure 2: IRIS containment systems.
rejection to the RWST prevents containment overpressuriza-tion and contributes to core cooling also thanks to dynamiccoupling between the primary and containment systems.
The DBA simulation on the facility allowed to under-stand the transient plant behaviour and the mutual systeminteraction. The comparison with the IRIS results led torunning many sensitivity cases that required the SPES3design review for better matching the IRIS transients.
The SPES3 tests will provide a qualified data base for theassessment of codes to be used in the reactor safety analyses.
The SPES3 facility is under construction, based on theIRIS reactor design. The availability of such a complex plantopens the way to other possibilities of exploitation, and
RWST
DW
RPV LGMS
PSS
RC
EHRS
EBT
QT
Figure 3: SPES3 facility layout.
studies are foreseen for using it in a wider field of applicationfor integral layout SMR simulation [8].
2. IRIS Plant and SPES3 FacilityLayout and Nodalization
The IRIS pressure vessel and containment are shown inFigures 1 and 2, whereas the SPES3 facility is presented inFigure 3.
The SPES3 facility reproduces all parts and compo-nents of the IRIS plant with 1 : 100 volume scaling factor,1 : 1 elevation scaling factor, and prototypical fluid andthermal-hydraulic conditions. The reactor vessel includesthe internals, consisting of the electrically heated coresimulator, the riser with control rod device mechanisms,the pressurizer, the pump suction plenum, the helical coilsteam generators, the downcomer, and the lower plenum.Three SGs simulate the eight IRIS SGs. A pump, locatedoutside of the RPV, for room reasons, and connected toit by pipes, simulates eight IRIS pumps. Two emergencyboration tanks are simulated and connected to the DVIlines, devoted to direct injection of emergency fluid into thevessel. Three secondary loops simulate four IRIS loops. Eachsecondary loop is simulated up to the main isolation valvesand includes the feed line, the SG, the steam line, and theemergency heat removal system with a vertical tube heatexchanger immersed in a refuelling water storage tank. TheIRIS spherical containment compartments are simulated bytanks, connected to each other by pipes and to the RPV bybreak lines [4, 5]. They include dry-well and reactor cavity,representing the dry zone surrounding the RPV, respectivelyabove and below the mid-deck plane; pressure suppressionsystems representing the wet zone around the lower part
Science and Technology of Nuclear Installations 3
Figure 4: IRIS primary and secondary circuit nodalization for RELAP5 code.
of the RPV, suitable to dump pressure in case of contain-ment pressurization; long-term gravity make-up systemsrepresenting the cold water reservoir to be poured into theRPV when depressurized. The two stages of the automaticdepressurization system are simulated, connected to thepressurizer top, with stage I discharging into the quench tankand stage II directly connecting RPV and DW at high plantelevation.
The facility allows to test both LOCAs and secondary sidebreaks (DBA and BDBA) as well as to perform separate effecttests on particular components such as SG-EHRS thermallycoupled to RWST.
The IRIS nodalization was developed in two parts: theprimary and secondary circuits for the RELAP5 code and thecontainment system for the GOTHIC code (Figures 4 and 5).The RELAP5 nodalization includes 1845 volumes, and 1940junctions, 1015 heat structures with 8600 mesh points, whilethe GOTHIC model includes 85 volumes, 28 junctions, and57 heat structures.
The SPES3 nodalization was completely developed forthe RELAP5 code (Figures 6, 7, and 8). It includes 1499 vol-umes, 1639 junctions, 1839 heat structures, and 19322 meshpoints.
3. Design-Calculation Feedback Process forSPES3 Facility Final Design
The RELAP5 model for SPES3 was initially developed onthe basis of the preliminary design of the facility, and thesteady-state conditions are based on the actual IRIS nominaloperation [9]. Five DBAs were simulated with particularattention to the occurring phenomena and sequence ofevents. In particular, three SB-LOCAs and two secondaryside breaks were simulated, according to the specified testmatrix [10].
Once the phenomena occurring in the DBAs were in-vestigated, attention was focused on the most challengingtransient scenario, the DVI line DEG break, for a directcomparison of the SPES3 and IRIS results.
WEC, in collaboration with the University of Pisa andPolitecnico di Milano, developed the Fractional ScalingAnalysis for IRIS and SPES3. The method, based on systemand time sequence decomposition, allowed to identify theparameters mostly affecting the transient and to quantify thedistortions between IRIS and SPES3 simulations introducedby such parameters (e.g., containment tank metal mass, heattransfer at core side wall, etc.).
4 Science and Technology of Nuclear Installations
2
1F
1
6
9 107 8
11
16/17
7 1 2
4 9
5
12
5F
15
10
3 518 19
12 13
21
14
6
15
11
23
3F/4F 13/14
1624/25
204
3 228
26/27/28
Environment
2F
6F/7F2 “Break
8F/9F/10F
ADS stage 1
ADS stage 2
Reactorcavity
Dry well
PSS-A PSS-B
PSS vent PSS vent
QT
DVI-A
LGMS-ALGMS-B
DVI-B
Ventextension
Ventextension
Figure 5: IRIS containment nodalization for GOTHIC code.
The first application of the DVI line DEG break ev-idenced important differences on containment pressure,especially in early phase of the accident, at pressure peak, andalso on the long term.
The need of understanding the reasons and reducingdiscrepancies led to performing a series of sensitivity caseson SPES3 containment, making SPES3 response closer toreactor one, and finalizing the facility design [11, 12].
The main events, identified in the DVI line breaktransient, are listed below for better understanding all sen-sitivity analyses and the design-calculation feedback process.Approximate timing of events is reported too. The long-termphase of the transient was simulated to verify the safe, stableplant operation.
(i) The break opening (0 s) causes the RPV blowdownand depressurization, containment pressurization,steam dumping into PSS with air build-up at PSS top,and consequent pressurization;
(ii) the signal of high containment pressure (∼30 s) trig-gers the reactor scram, the secondary loop isolation,and the actuation of two out of four EHRSs;
(iii) the signal of low PRZ water level (∼120 s) triggersthe pump coastdown, and the natural circulationin the core is guaranteed through the check valves,connecting riser and downcomer at one-third of theSG height;
(iv) the signal of low PRZ pressure (∼200 s) actuates theremaining EHRS and triggers the ADS stage I, to help
RPV depressurization, and the EBT intervention, toinject cold water into the primary circuit;
(v) the signal of low differential pressure between RPVand DW (∼2250 s) triggers the LGMS injection intothe DVI line and opens the valves connecting RCand DVI line to allow water reverse flow from thecontainment to the primary side;
(vi) when PSS pressurization is sufficiently high, coldwater flows from PSS to DW (3500 s), increasing theRC flooding and allowing water to enter the RPV;
(vii) the signal of low LGMS mass (∼25000 s) opens theADS stage II with possible reverse steam flow fromDW to RPV;
(viii) on the long term (simulation up to 100000 s), theplant is cooled by EHRSs that reject core decay heatto RWST.
The starting point for the sensitivity analyses was thecomparison between cases SPES3-97 and IRIS-HT1 results,which showed qualitatively good agreement in occurringphenomena, but also quantitative discrepancies in contain-ment pressure, affecting the sequence of events and transientevolution (Figure 9).
A series of parameters identifying and potentially affect-ing containment pressure is: (a) SPES3 containment over-volume of about 10% with respect to 1 : 100 scaled IRIS;(b) SPES3 containment metal mass greater than IRIS formechanical resistance to the same design conditions; (c)
Science and Technology of Nuclear Installations 5
Figure 6: SPES3 primary circuit nodalization for RELAP5 code.
SPES3 component surface-to-volume ratio ten times greaterthan IRIS, due to volume scaling and component heightconservation; (d) containment metal structure temperature;(e) containment piping pressure drops; (f) EHRS and RWSTmodelling and heat transfer coefficients.
A synthesis of the performed sensitivity cases on SPES3 isreported in Table 1, where they are grouped according to theinvestigated parameters. A synthesis of IRIS cases, utilised forthe comparison, is reported in Table 2.
A reduction of DW volume, for correctly scaling IRIS(1 : 100), did not provide great improvements (a few percent)in the containment pressure response. An improvement wasobserved only in the long term related to lower heat losses toenvironment due to DW size reduction (Figure 10).
In order to compensate for the extra surface in SPES3,a thermal insulation of DW inner surface was tested withdifferent thickness of Aluminium Silicate Rescor 902. Asshown in Figure 11, the introduction of an increasing
6 Science and Technology of Nuclear Installations
Figure 7: SPES3 secondary circuit and EHRS nodalization for RELAP5 code.
Figure 8: SPES3 containment nodalization for RELAP5 code.
thickness of thermal insulation increased pressure in the veryshort term, but the additional mass reduced the containmentpressure peak. The result was that the DW insulation ledto worse effects on pressure than with noninsulated DW,showing that masses have larger effects than surfaces.
The influence of DW heat structure mass on containmentpressure response was investigated by reducing DW thicknessby 40% (25 mm to 15 mm), approximately correspondingto a design pressure of 1.5 MPa, instead of the original2 MPa. As shown in Figure 12, pressure increase in the early
Science and Technology of Nuclear Installations 7
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
0 20000 40000 60000 80000 100000
Time (s)
Pre
ssu
re(P
a)
p 401140000PR1s54∗1000
SPES3-97IRIS-HT1
Figure 9: SPES3-97 and IRIS-HT1 DW pressure. Note: The IRISDrywell Volume was subdivided in 4x4x4 sub-volumes in the threedirections, marked 1s1, 1s2. . . up to 1s64. Pressure from a cell at thetop of the model was used as reference.
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
0 20000 40000 60000 80000 100000
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54∗1000
SPES3-97SPES3-99
Figure 10: SPES3-97, 99 and IRIS-HT1 DW pressure.
phase of the transient was steeper and pressure peak higher.Containment pressure was still below the IRIS one, showingthat such DW metal mass reduction was not enough to havethe desired pressure response.
A further DW mass reduction was performed in atheoretical case, where concrete plus carbon steel IRIS DWequivalent mass was distributed on SPES3 DW surface,resulting in a thickness of 10 mm AISI 304. As shown inFigure 13, the further DW mass reduction allowed to getpressure values closer to IRIS both in the early phases ofthe transient and at the pressure peak, but still below IRISpressure. That showed that other parameters affected theresults.
An attempt to investigate how a greater DW volumereduction affects containment pressure was performed byscaling it 1 : 150 with respect to IRIS. Figure 14 shows apressure gain only in the early phases of the transient
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
0 2000 4000 6000 8000 10000
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000p 401140000PR1s54 1000
SPES3-100SPES3-103
SPES3-99
Figure 11: SPES3-99, 100, 103 and IRIS-HT1 DW pressure (shortterm).
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54 1000
SPES3-104SPES3-99
0 2000 4000 6000 8000 10000
Figure 12: SPES3-99, 104 and IRIS-HT1 DW pressure (short term).
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54 1000
SPES3-99SPES3-105
0 2000 4000 6000 8000 10000
Figure 13: SPES3-99, 105 and IRIS-HT1 DW pressure (short term).
8 Science and Technology of Nuclear Installations
Ta
ble
1:C
har
acte
rist
ics
ofth
eSP
ES3
case
s.
SPE
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ses
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siti
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mm
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nta
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ent
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ter
phas
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ted
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IS.
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eat
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ctu
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ture
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onal
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om7.
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Science and Technology of Nuclear Installations 9
Ta
ble
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nu
ed.
SPE
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arac
teri
stic
seff
ect
for
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to2.
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om5.
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.
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ith
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onal
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mal
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gin
ally
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tof
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ted
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ale
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tof
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ere
duce
dto
corr
ectl
ysi
mu
late
IRIS
surf
ace.
Sen
siti
vity
onth
eco
nta
inm
ent
pipi
ng
pres
sure
drop
s
SPE
S3-1
09P
SSm
ain
ven
tpi
pere
sizi
ng
from
2.5′′ t
o2′′ S
ch.4
0.P
SSve
nt
pipe
exte
nsi
onre
sizi
ng
from
3/4′′ t
o1/
2′′ S
ch.4
0P
SSto
DW
mas
sfl
owcl
oser
toIR
ISon
e.
SPE
S3-1
10P
SSm
ain
ven
tpi
pead
diti
onal
rest
rict
ion
atth
ech
eck
valv
e(D
orifi
ce14
.19
mm
)O
nly
earl
yst
eep
but
limit
edco
nta
inm
ent
pres
sure
incr
ease
.
SPE
S3-1
18
Con
tain
men
tvo
lum
esc
aled
1:1
00on
IRIS
.LG
MS
toD
VI
line
calib
rate
dor
ifice
from
3.2
mm
to2.
3m
m.
EH
RS-
CC
Lca
libra
ted
orifi
cefr
om8.
5m
mto
6.5
mm
.P
SSve
nt
pipe
exte
nsi
onad
diti
onal
rest
rict
ion
(Dor
ifice
5.2
mm
).C
onta
inm
ent
hea
tst
ruct
ure
init
ialt
empe
ratu
re48
.9◦ C
Att
empt
tom
atch
IRIS
inje
ctio
nm
ass
flow
s.
SPE
S3-1
20
Con
tain
men
tvo
lum
esc
aled
1:1
00on
IRIS
.T
hic
knes
sto
resi
st1.
5M
Pade
sign
pres
sure
.A
irsp
ace
met
alst
ruct
ure
init
ialt
empe
ratu
re84
◦ C.Q
Tin
itia
ltem
pera
ture
48.9◦ C
.LG
MS
toD
VI
line
calib
rate
dor
ifice
from
2.3
mm
to2.
5m
m
IRIS
inje
ctio
nm
ass
flow
repr
odu
ced,
but
diff
eren
tpr
essu
redr
ops
inth
epi
pes.
SPE
S3-1
24
PSS
mai
nve
nt
pipe
resi
zin
gfr
om2′′ t
o2.
5′′ S
ch.4
0P
SSve
nt
pipe
exte
nsi
onre
sizi
ng
from
1/2′′ t
o1′′ S
ch.4
0LG
MS
toD
VI
line
calib
rate
dor
ifice
from
2.5
mm
to3.
6m
m.
PSS
ven
tpi
peex
ten
sion
orifi
cefr
om7.
3to
19m
m.
PSS
ven
tpi
peex
ten
sion
con
nec
tion
toD
Wel
evat
ion
decr
ease
of1.
5m
tom
atch
IRIS
.P
SSsp
arge
rel
evat
ion
decr
ease
of0.
25m
tom
atch
IRIS
.P
SSbo
ttom
mod
elle
dw
ith
abr
anch
.C
onta
inm
ent
air
spac
em
etal
stru
ctu
rein
itia
ltem
pera
ture
84◦ C
,wat
ersp
ace
48.9◦ C
Mas
sfl
owde
term
ined
byac
tual
pipi
ng
pres
sure
drop
sas
inIR
IS.C
onta
inm
ent
pres
sure
resp
onse
qual
itat
ivel
yan
dqu
anti
tati
vely
clos
eto
IRIS
.T
he
PSS
bott
omm
odel
ling
did
not
affec
tth
eP
SSve
nt
pipe
empt
yin
gm
ode.
10 Science and Technology of Nuclear Installations
Ta
ble
1:C
onti
nu
ed.
SPE
S3ca
ses
Ch
arac
teri
stic
seff
ect
for
mas
sR
esu
lts
SPE
S3-1
27A
sSP
ES3
-124
PSS
bott
omm
odel
led
wit
hth
ree
bran
ches
.T
he
PSS
bott
omm
odel
ling
did
not
stro
ngl
yaff
ect
the
PSS
ven
tpi
peem
ptyi
ng
mod
e.
SPE
S3-1
30A
sSP
ES3
-127
RW
STto
ppi
pein
trod
uct
ion
for
con
nec
tion
toat
mos
pher
e.R
edu
ced
loss
ofm
ass
atR
WST
top
due
todr
yai
ran
dw
ater
con
tact
.
SPE
S3-1
35
AS
SPE
S3-1
32C
ompl
etel
yre
view
edth
eE
HR
Sci
rcu
its
and
RW
STm
odel
:E
HR
S-A
and
Btu
be4%
surf
ace
ther
mal
lyin
sula
ted
wit
hTe
flon
oth
erth
anth
eor
igin
ally
insu
late
d0.
6tu
bes.
EH
RS-
C4%
surf
ace
ther
mal
lyin
sula
ted
oth
erth
anth
eor
igin
ally
insu
late
d0.
2tu
bes.
EH
RS-
Aan
dB
HL
resi
zed
from
2′′ t
o1.
25′′
Sch
.80.
EH
RS-
Aan
dB
CL
resi
zed
from
1.25
′′to
1.5′′ S
ch.8
0.E
HR
S-C
HL
resi
zed
from
2.5′′ t
o2′′ S
ch.8
0.E
HR
S-C
CL
resi
zed
from
1.5′′ t
o3′′ S
ch.8
0.H
L-A
and
Bad
diti
onal
orifi
ceD=
17m
m.
HL-
Cad
diti
onal
orifi
ceD
=24
mm
.C
L-A
and
Bor
ifice
resi
zed
from
5m
mto
5.9
mm
.C
L-C
orifi
cere
size
dfr
om7
mm
to8.
3m
m.
EH
RS
tube
hea
tst
ruct
ure
fou
ling
fact
orse
tto
2.9
left
and
2.77
righ
t(o
rigi
nal
valu
es2.
725
left
,3.5
4284
righ
t)[1
3].
RW
ST-A
Ban
dC
risi
ng
slic
ear
eare
size
dfr
om0.
491
m2
to0.
1191
67m
2;r
ecir
cula
tion
slic
ere
size
dfr
om1.
217
m2
to1.
6011
69m
2[1
3].
RW
ST-A
Ban
dC
slic
esi
deju
nct
ion
area
from
0.15
1m
2to
0.13
5m
2[1
3].
Th
eco
mpl
ete
revi
sion
ofth
eE
HR
Spi
pin
gan
dh
eat
exch
ange
rpa
ram
eter
sle
dto
mat
chin
gtr
ansf
erre
den
ergy
.
SPE
S3-1
46A
sSP
ES3
-135
.P
SSve
nt
pipe
exte
nsi
onor
ifice
from
19m
mto
17.5
mm
.SG
tube
inle
tor
ifice
from
12.5
mm
to11
.7m
m
Goo
dsi
mila
rity
betw
een
SPE
S3an
dIR
ISB
ASE
CA
SEfo
rFS
Afi
nal
appl
icat
ion
.
Science and Technology of Nuclear Installations 11
Table 2: Characteristics of the IRIS cases.
IRIS cases Characteristics Results
IRIS-HT1 Containment heat structures simulated only for the DW. Starting point for comparison with SPES3.
IRIS-HT5g
Heat structures added to all containment compartments and secondarysidepiping.PSS main vent pipe connection to DW rise of 4 m.PSS sparger set at 0.75 m from PSS bottom.RWST remodelled with parallel slice approach.
Similar containment pressure response withSPES3.
IRIS-HT6 rwstc
SG tubes inner layer removed which simulated the Fouling.ADS stage II actuation signal corrected to intervene on low LGMS mass.RWST remodelling according to PERSEO area ratio and HTC calibrationon experimental data. EHRS heat transfer parameters set as in SPES3 (bymultiplier fouling factors) [12, 13].RWST top pipe introduction for connection to atmosphere.Correction of energy transfer parameters at the GOTHIC and RELAP5code couplings.
Better matching of EHRS long-term energytransfer to RWST.
IRIS-HT6 rwstc1a
Corrected elevation difference between the RELAP5 and GOTHIC parts ofthe model: the ADS stage I vent pipe end should be 0.5 m from QT bottom(it was connected to QT top); LGMS tanks rise of 0.75 m.
Results very similar to IRIS-HT6 rwstcBASE CASE for FSA final application.
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
SPES3-106SPES3-104IRIS-HT1
p 401140000p 401140000PR1s54 1000
0 2000 4000 6000 8000 10000
Figure 14: SPES3-104, 106 and IRIS-HT1 DW pressure (shortterm).
with a lower peak value. No improvement was obtained byoverreducing the DW volume with a scaling factor differentfrom 1 : 100.
A theoretical case, where IRIS DW structures weredirectly scaled 1 : 100 in mass and surface, was investigated.A one-hundredth vertical slice of IRIS DW structures wasattributed to SPES3 DW, maintaining the same thickness andmaterial composition. Figure 15 compares two cases withequivalent heat structure masses, but different surfaces andmaterial properties. Pressure increase was similar in IRIS andSPES3, in the early phase of the transient, when surface hasa greater impact, but later energy transfer to heat structuresprevailed and SPES3 pressure did not increase as expected,with all SPES3 containment structures being completelysimulated against the only IRIS DW structure simulation.Moreover, gas space volume at the PSS and LGMS topwas about 14% higher in SPES3 than IRIS, so limiting
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54 1000
SPES3-108SPES3-105
0 2000 4000 6000 8000 10000
Figure 15: SPES3-105, 108 and IRIS-HT1 DW pressure (shortterm).
the containment pressure peak. Containment pressure trendshowed also differences in the depressurization phase, relatedto steam condensation in RC and DW due to broken loopLGMS water entering the RC (∼2000 s in SPES3) throughthe DVI break line, containment side, and PSS injection intothe DW (∼3000 s in SPES3). Injection mass flows are shownin Figures 16 and 17, and they depended on different pipepressure drops and containment pressurization.
An attempt to make closer SPES3 and IRIS PSS toDW injection mass flows was performed: size of PSS mainvent pipe and extension was decreased and the resultscompared with a base case (SPES3-107) equivalent to SPES-99, where minor input mistakes were corrected. PSS injectionresults were effectively closer to IRIS with consequent slowercontainment depressurization (Figures 18 and 19).
The attempt was performed to see how a restriction at thePSS main vent pipe check valve affects the steam-air transfer
12 Science and Technology of Nuclear Installations
−0.020
0.020.040.060.08
0.10.120.140.160.18
0.2
0 1000 2000 3000 4000 5000 6000 7000 8000900010000
Time (s)
Mas
sfl
ow(k
g/s)
mflowj 423000000 LGMS-Amflowj 433000000 LGMS-B
FL7/100 LGMS-AFL12/100 LGMS-B
SPES3-108
IRIS-HT1
Figure 16: SPES3-108 and IRIS-HT1 LGMS to DVI injection massflow (short term).
−2
−1.5
−1
−0.5
0
0.5
1
1.5
2
2.5
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Time (s)
Mas
sfl
ow(k
g/s)
mflowj 47002 + 473 VENT-Amflowj 48002 + 483 VENT-BFV + FL + FD04 VENT-AFV + FL + FD09 VENT-B
IRIS-HT1
SPES3-108
Figure 17: SPES3-108 and IRIS-HT1 PSS to DW injection massflow (short term). Note: for IRIS, the total mass flow (FL + FV +FD) is obtained by the sum of phasic mass flows (liquid, gas anddroplets.
from DW to PSS and eventually rise DW pressure. The resultwas a steep but limited pressure increase (Figure 20).
The impossibility of reducing the DW thickness under15 mm, to resist 1.5 MPa design pressure, led necessarily toan excess of mass with respect to IRIS 1 : 100 scaled mass.In SPES3-105 case, the IRIS scaled mass was distributed onthe SPES3 DW surface obtaining an equivalent thicknessof 10 mm. The possibility of compensating for 5 mm extramass, by preheating the DW heat structures, was investigated.The preheating temperature of 84◦C was estimated byan energy balance between the cases with 10 mm and15 mm thickness from the specified initial temperature of48.9◦C and regime temperature of 172◦C after the heat-uptransient. Figure 21 compares the cases with 15 mm (SPES3-104), 10 mm (SPES3-105), and 15 mm (SPES3-111) pre-heated DW thickness. The 10 mm and 15 mm pre-heated
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Time (s)−3
−2
−1
0
1
2
3
Mas
sfl
ow(k
g/s)
mflowj 47002 + 473 VENT-Amflowj 48002 + 483 VENT-Bmflowj 47002 + 473 VENT-Amflowj 48002 + 483 VENT-BFV + FL + FD04 VENT-AFV + FL + FD09 VENT-B
IRIS-HT1
SPES3-107
SPES3-109
Figure 18: SPES3-109, 107 and IRIS-HT1 PSS to DW injectionmass flow (short term).
SPES3-109SPES3-107
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54 1000
0 2000 4000 6000 8000 10000
Figure 19: SPES3-109, 107 and IRIS-HT1 DW pressure (shortterm).
DWs are equivalent showing that heat structure preheatingcompensates for the excess of mass in SPES3. Only DWpreheating is not enough to have the same IRIS pressureresponse.
The comparison between the cases with and withoutPSS heat structures allowed to quantify the phenomenonof air cooling when steam-air mixture flowed from DW toPSS. The run was interrupted by a nonconvergence erroron noncondensable gas properties in the PSS, but availableresults allowed to evaluate the pressure gain, with respect tothe theoretical case with 1 : 100 IRIS DW volume and surfacescaled structures, as shown in Figure 22.
In order to reduce distortions on pressure as muchas possible, related to scaling mismatching, all the SPES3containment compartments were scaled 1 : 100 on IRISvolumes and all thicknesses were sized to resist 1.5 MPa
Science and Technology of Nuclear Installations 13
SPES3-110SPES3-109
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000PR1s54 1000
0 2000 4000 6000 8000 10000
Figure 20: SPES3-110, 109 and IRIS-HT1 DW pressure (shortterm).
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000p 401140000
PR1s54 1000
SPES3-111SPES3-105SPES3-104
0 2000 4000 6000 8000 10000
Figure 21: SPES3-111, 105, 104 and IRIS-HT1 DW pressure (shortterm).
pressure, so limiting the thermal inertia of the metal walls.In particular, the containment air zone heat structures werepreheated at 84◦C, while those in the liquid zone werekept at 48.9◦C. Moreover, the calibrated orifices on theLGMS to DVI lines, the ADS stage I, and EHRS-C CL wereresized to match IRIS mass flows. Figure 23 shows that,notwithstanding a slower DW pressure increase, that case issimilar to the case with IRIS DW scaled 1 : 100 in mass andsurface (SPES3-108), confirming that containment volumeresizing and heat structure preheating are good solutionstoward IRIS containment pressure response. Orifice resizingwas not enough to match the IRIS LGMS to DVI andEHRS-C CL mass flows, while it was correct to scale ADSstage I mass flow (Figure 24), even if a stronger waterentrainment was evidenced in IRIS at the second flow peak.
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000
PR1s54 1000
SPES3-112SPES3-108
0 2000 4000 6000 8000 10000
Figure 22: SPES3-112, 108 and IRIS-HT1 DW pressure (shortterm).
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Time (s)
Pre
ssu
re(P
a)
IRIS-HT1
p 401140000p 401140000p 401140000
PR1s54 1000
SPES3-115SPES3-108SPES3-107
0 2000 4000 6000 8000 10000
Figure 23: SPES3-115, 108, 107 and IRIS-HT1 DW pressure (shortterm).
Further calibrations of the injection line orifices wereperformed that evidenced contact condensation stronger inSPES3 (RELAP5) than in IRIS (GOTHIC).
A case was run where IRIS containment heat structureswere reproduced on SPES3 with the DW 1 : 100 scaled inmass and surface and all other tanks with 1 mm thick wallsto avoid code convergence errors in case of complete heatstructure removal. Figure 25 shows very similar SPES3 andIRIS containment pressure rising phase and a pressure peakonly 0.1 MPa lower in SPES3 than in IRIS, demonstrating theimportance of a correct simulation of the heat structures.
The containment piping orifice, sized to match IRISinjection mass flows, allowed a direct comparison betweenthe plants, but it did not meet the piping pressure dropscaling criteria. It allowed to understand two important
14 Science and Technology of Nuclear Installations
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Time (s)
Mas
sfl
ow(k
g/s)
mflowj 143000000 DTmflowj 153000000 STmflowj 982 + 983/100 DTmflowj 981/100 ST
SPES3-115
IRIS-HT1
Figure 24: SPES3-115 and IRIS-HT1 ADS stage I ST and DT massflow (short term).
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
Pre
ssu
re(P
a)
0 5000 10000 15000 20000 25000 30000Time (s)
p 401140000PR1s54∗1000 IRIS-HT1
SPES3-119
Figure 25: SPES3-119 and IRIS-HT1 DW pressure (short term).
differences related to the injection of LGMS into the DVIlines and of PSS into the DW. As shown in Figures 26and 27, IRIS LGMS injection into the DVI line is alwaysdriven by differential pressure between LGMS and DVI line(until about 18700 s), instead in SPES3, such differentialpressure extinguishes earlier (around 9200 s) and later LGMSinjection is driven only by gravity with a large mass flowdecrease. The reason for such early pressure equalizationin SPES3 is related to the PSS injection stop, vent pipeemptying, and gas flow from PSS to DW. That phenomenondid not occur in IRIS, where the vent pipes did not emptyavoiding air transfer from PSS to DW, keeping the PSSpressurized with respect to DW and DVI (Figure 28).
The sensitivity cases on containment tank geometry, heatstructures, and piping pressure drops led to reviewing boththe IRIS and SPES3 models in IRIS-HT5g and SPES3-124. AllIRIS containment heat structures were simulated and SPES3piping geometry was adjusted to match IRIS pressure drops.
0 5000 10000 15000 20000 25000 30000 35000 40000
Time (s)−0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
Mas
sfl
ow(k
g/s)
mflowj 423000000 LGMS-Amflowj 433000000 LGMS-BFL7/100 LGMS-AFL12/100 LGMS-B
IRIS-HT1
SPES3-120
Figure 26: SPES3-120 and IRIS-HT1 LGMS injection mass flow.
0E + 00
2E + 05
4E + 05
6E + 05
8E + 05
1E + 06
1.2E + 06
1.4E + 06
1.6E + 06
1.8E + 06
2E + 06
0 5000 10000 15000 20000 25000 30000 35000 40000
Time (s)
Pre
ssu
re(P
a)
p 406060000 LGMS-Ap 408060000 LGMS-Bp 6010100000 DVI-Ap 630100000 DVI-BPR7∗1000 LGMS-APR8∗1000 LGMS-BP 604401 DVI-AP 62401 DVI-B
IRIS-HT1
SPES3-120
Figure 27: SPES3-120 and IRIS-HT1 LGMS and DVI pressure.
Figure 29 compares SPES3 and IRIS containment pres-sures, showing a good qualitative and quantitative agree-ment. The LGMS to DVI and PSS to DW injection massflows are shown in Figures 30 and 31. With the samesimulated pressure drops in the piping, different values ofmass flow are evidenced due to greater differential pressuresin SPES3 between LGMS and DVI and PSS and DW. Variousreasons could explain these differences and the most likelyis the different code simulation of contact condensationwith the consequent different pressurization of containmentcompartments. Remodelling of IRIS RWST led to similarRWST water temperatures, but greater exchanged power inSPES3 caused faster heat-up (Figure 32).
Science and Technology of Nuclear Installations 15
0
5
10
15
20
25
0 5000 10000 15000 20000 25000 30000 35000 40000Time (s)
Leve
l(m
)
cntrlvar 1439 VENT-Acntrlvar 1441 VENT-BLL14-12 + LL4-1.5 VENT-ALL15-12 + LL6-1.5 VENT-B
IRIS-HT1
SPES3-120
Figure 28: SPES3-120 and IRIS-HT1 PSS vent pipe level.
0E + 001E + 052E + 053E + 054E + 055E + 056E + 057E + 058E + 059E + 051E + 06
0 20000 40000 60000 80000 100000
Time (s)
Pre
ssu
re(P
a)
p 401140000PR1s54∗1000 IRIS-HT5g
SPES3-124
Figure 29: SPES3-124 and IRIS-HT5g DW pressure.
−0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0 10000 20000 30000 40000 50000
Time (s)
Mas
sfl
ow(k
g/s)
mflowj 423000000 LGMS-Amflowj 433000000 LGMS-BFL7/100 LGMS-AFL12/100 LGMS-B
IRIS-HT5g
SPES3-124
Figure 30: SPES3-124 and IRIS-HT5g LGMS to DVI mass flow(short term).
−3
−2.5
−2.0
−1.5
−1
−0.5
0
0.5
1
0 1000 2000 3000 4000 5000 6000 7000 8000 900010000
Time (s)
Mas
sfl
ow(k
g/s)
mflowj 47002 + 473 VENT-Amflowj 48002 + 483 VENT-B(FV + FL + FD4)/100 VENT-A(FV + FL + FD9)/100 VENT-B
IRIS-HT5g
SPES3-124
Figure 31: SPES3-124 and IRIS-HT5g PSS to DW mass flow (shortterm).
0
50
100
150
200
250
300
350
400
450
0 20000 40000 60000 80000 100000
Time (s)
Tem
pera
ture
(K)
tempf 520180000 RWST-ABtempf 825010000 RWST-Ctempf 58001 RWST-Atempf 59001 RWST-B
IRIS-HT5g
SPES3-124
Figure 32: SPES3-124 and IRIS-HT5g RWST temperature.
0 20000 40000 60000 80000 100000
Time (s)
0E + 001E + 052E + 053E + 054E + 055E + 056E + 057E + 058E + 059E + 051E + 06
Pre
ssu
re(P
a)
p 401140000
PR1s54∗1000 IRIS-HT5g
SPES3-127
Figure 33: SPES3-127 and IRIS-HT5g DW pressure.
16 Science and Technology of Nuclear Installations
0 20000 40000 60000 80000 100000
Time (s)
IRIS-HT5g
SPES3-127
0
50
100
150
200
250
300
350
400
Tem
per
atu
re(K
)
tempf 520180000 RWST-ABtempf 820180000 RWST-Ctempf 58001 RWST-Atempf 59001 RWST-B
Figure 34: SPES3-127 and IRIS-HT5g RWST temperature.
0 20000 40000 60000 80000 100000
Time (s)−200
0
200
400
600
800
1000
1200
1400
Mas
s(k
g)
RWST out tot massRWST out tot mass IRIS-HT5g
SPES3-127
Figure 35: SPES3-127 and IRIS-HT5g RWST top integral massflow.
The SPES3 PSS bottom remodelling was the furtherattempt to investigate PSS vent pipe emptying at the end ofPSS injection into the DW. No important differences wereobserved. The SPES3-127 results were used to investigatethe EHRS heat transfer to RWST, considered the cause ofthe different containment pressure trend in the long term,where IRIS increased after 50000 s while SPES3 continued todecrease (Figure 33). RWST temperature in SPES3 did notreach saturation, but established at lower values (Figure 34),due to the direct connection, in the model, of RWST topwith the atmosphere control volume, and mass lost throughRWST top caused by water solution in dry air with energyremoval and temperature limitation (Figure 35).
That phenomenon led to a further modification of themodel with the introduction of a discharge pipe at RWSTtop, limiting the contact surface with air and solving theproblem of RWST water temperature that, finally, could
0 20000 40000 60000 80000 100000
Time (s)
250
270
290
310
330
350
370
390
Tem
per
atu
re(K
)
tempf 520180000 RWST-ABtempf 820180000 RWST-Ctempf 520180000 RWST-ABtempf 820180000 RWST-Ctempf 58001 RWST-Atempf 59001 RWST-B
SPES3-130
IRIS-HT5g
SPES3-127
Figure 36: SPES3-130, 127 and IRIS-HT5g RWST temperature.
0 20000 40000 60000 80000 100000
Time (s)
0E + 00
1E + 05
2E + 05
3E + 05
4E + 05
5E + 05
6E + 05
7E + 05
8E + 05
9E + 05
1E + 06
Pre
ssu
re(P
a)
p 401140000
PR1s54∗1000
SPES3-146
IRIS-HT6 rwstc
Figure 37: SPES3-146 and IRIS-HT6 rwstc DW pressure.
0 20000 40000 60000 80000 100000
Time (s)
SPES3-146
IRIS-HT6 rwstc
0E + 00
2E + 06
4E + 06
6E + 06
8E + 06
1E + 07
1.2E + 07
1.4E + 07
1.6E + 07
1.8E + 07
Pre
ssu
re(P
a)
p 130150000P 13015
Figure 38: SPES3-146 and IRIS-HT6 rwstc PRZ pressure.
Science and Technology of Nuclear Installations 17
0
Time (s)−0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Mas
sfl
ow(k
g/s)
mflowj 607000000 EBT-Amflowj 627000000 EBT-BMFLOWJ 605/100 EBT-AMFLOWJ 625/100 EBT-B
SPES3-146
IRIS-HT6 rwstc
0 2000 4000 6000 8000 10000
Figure 39: SPES3-146 and IRIS-HT6 rwstc EBT injection massflow (short term).
0 20000 40000 60000 80000 100000
Time (s)
SPES3-146
IRIS-HT6 rwstc
−0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Mas
sfl
ow(k
g/s)
mflowj 423000000 LGMS-Amflowj 433000000 LGMS-BFL7/100 LGMS-AFL12/100 LGMS-B
Figure 40: SPES3-146 and IRIS-HT6 rwstc LGMS to DVI injectionmass flow.
reach saturation (Figure 36). Faster water heat-up in SPES3showed that EHRS energy transfer to the RWST is greaterthan IRIS. That led to a series of sensitivity cases on astand-alone model of EHRS-RWST that led to investigatingthe differences between the models and finding a commonmodelling approach based on experimental data on anin-pool heat exchanger and literature values of the heattransfer coefficients [13]. The method provided propermultiplying factors for the HTC to be applied to tube heatstructures, condensing and boiling side, in the form offouling factors [14] and a criterion to set the area of the poolslice containing the heat exchanger. IRIS EHRS-RWST wasmodified accordingly in the IRIS-HT6 rwstc case. A stand-alone model was also utilized to calibrate pressure drops in
Time (s)−3
−2.5
−2
−1.5
−1
−0.5
0
0.5
1
Mas
sfl
ow(k
g/s)
mflowj 47002 + 473 VENT-Amflowj 48002 + 483 VENT-B(FV + FL4 + FD4)/100 VENT-A(FV9 + FL9 + FD9)/100 VENT-B
SPES3-146
IRIS-HT6 rwstc
0 2000 4000 6000 8000 10000
Figure 41: SPES3-146 and IRIS-HT6 rwstc PSS to DW injectionmass flow (short term).
Time (s)−2E + 06
0E + 00
2E + 06
4E + 06
6E + 06
8E + 06
1E + 07
1.2E + 07
Pow
er(W
)
cntrlvar 541SG total power (CNTRLVAR51 + 52 + 53 + 54 + 55 + 56 + 57 + 58)/100
SPES3-146
IRIS-HT6 rwstc
0 2000 4000 6000 8000 10000
Figure 42: SPES3-146 and IRIS-HT6 rwstc SG power (short term).
0E + 00
1E + 05
2E + 05
3E + 05
4E + 05
5E + 05
6E + 05
7E + 05
8E + 05
Pow
er(W
)
cntrlvar 582 RWST-ABcntrlvar 585 RWST-CCNTRLVAR 3510/100 RWST-ACNTRLVAR 3520/100 RWST-B
SPES3-146
IRIS-HT6 rwstc
0 20000 40000 60000 80000 100000
Time (s)
Figure 43: SPES3-146 and IRIS-HT6 rwstc RWST power.
18 Science and Technology of Nuclear Installations
0 20000 40000 60000 80000 100000
Time (s)
0
500
1000
1500
2000
2500
3000
3500
Mas
s(k
g)
cntrlvar 408CNTRLVAR 3219/100
SPES3-146IRIS-HT6 rwstc
Figure 44: SPES3-146 and IRIS-HT6 rwstc RV mass.
0 20000 40000 60000 80000 100000
Time (s)
300
350
400
450
500
550
600
650
Tem
pera
ture
(K)
httemp 110100110 bottomhttemp 110101110 middlehttemp 110102110 topHTTEMP 110100110 bottomHTTEMP 110101110 middleHTTEMP 110102110 top
SPES3–146
IRIS-HT6 rwstc
Figure 45: SPES3-146 and IRIS-HT6 rwstc core heater rod outersurface temperature.
EHRS hot legs and cold legs to properly reproduce the IRISloops with adjustment to calibrated orifices. Moreover, theneed of thermally insulating 4% of SPES3 HX heat transfersurface was evidenced to compensate for AISI 304 thermalconductivity greater than IRIS Inconel 600.
The SPES3-146 case included all design and modelupdates previously described and was considered the basecase to compare to IRIS-HT6 rwstc. The main quantitiesof the transient and those that were objective of the SPES3facility model and design optimization are shown in Figures37, 38, 39, 40, 41, 42, 43, 44, and 45.
The last IRIS case was successively run to correct somedifferences, found in RELAP5 and GOTHIC models, aboutthe end elevations of LGMS and ADS stage I lines. Smalldifferences, compared to IRIS-HT6 rwstc results, were foundin LGMS flows as well as some changes in ADS stage I
flow, after initial discharge. Such differences do not affect ormodify the results of the analysis previously described.
The final FSA is planned to be performed on the SPES3-146 and IRIS-HT6 rwstc1a results.
4. Conclusions
The design of the SPES3 facility was finalized thanks to aniterative calculation-design feedback process that allowed toverify the adequacy of containment pressure and reactorvessel mass inventory simulation, objectives of the SBLOCAPIRT for the IRIS reactor [7].
Since the early simulations, efficiency of IRIS safetysystems was demonstrated in coping with SBLOCAs. Thecomparison with the SPES3 results and the early applicationof the FSA allowed to identify the main causes of discrep-ancy between the results and to put in evidence specificphenomena particularly affected by simulation choices. Thecontainment heat structures, the heat transfer from EHRSto RWST, and piping pressure drops were found to be themost affecting parameters in matching the IRIS results. Thereview of the SPES3 design, in accordance to the above-mentioned parameter optimization, led to demonstratingthat the PIRT identified FoMs are satisfied and that theresidual discrepancies can be considered conservative: SPES3RPV mass lower than IRIS mass and SPES3 heater rodtemperatures higher than IRIS ones.
Besides the SPES3 design review, the main outcomeof this work is the availability of a set of data suitablefor the final FSA application, in progress at the moment,and the quantification of SPES3 facility distortions in IRISsimulation.
The SPES3 facility is under construction at SIET labora-tories.
Nomenclature
ADS: Automatic depressurization systemCIRTEN: Consorzio Interuniversitario per la Ricerca
Tecnologica Nucleare (University Consortiumfor Nuclear Technologic Research)
CL: Cold Legcntrlvar: (CNTRLVAR) control variable (RELAP5
variable)CRDM: Control rod drive mechanismDBA: Design basis accidentDC: DowncomerDEG: Double ended guillotineDT: Double trainDVI: Direct vessel injectionDW: Dry wellEBT: Emergency boration tankEHRS: Emergency heat removal system (EHRS-A, B, C
for loops A, B, C)ENEA: Agenzia Nazionale per le Nuove Tecnologie,
l’Energia e lo Sviluppo Economico Sostenibile(Italian National Agency for New Technologies,Energy and Sustainable EconomicDevelopment)
Science and Technology of Nuclear Installations 19
FD: Droplet mass flow rate (GOTHIC variable)FER: Fakultet Elektrotehnike i Racunarstva (Faculty
of Electric Engineering and Computing) FLFeed Line
FL: Liquid mass flow rate (GOTHIC variable in thegraphs)
FoM: Figure of meritFSA: Fractional scaling analysisFV: Gas mass flow rate (GOTHIC variable)GNEP: Global nuclear energy partnershipGOTHIC: Generation of thermal-hydraulic information
for containmentsHTC: Heat transfer coefficienthttemp: (HTEMP) heat structure temperature
(RELAP5 variable)HX: Heat exchangerIRIS: International reactor innovative and secureITF: Integral test facilityLGMS: Long-term gravity make-up systemLL: Liquid level (GOTHIC variable)LOCA: Loss of coolant accidentLP: Lower plenumLWR: Light water reactormflowj: (MFLOWJ) mass flow rate (RELAP5 variable)NPP: Nuclear power plantp: (P) Pressure (RELAP5 variable)PIRT: Phenomena identification and ranking tablePR: Pressure (GOTHIC variable)PRZ: PressurizerPSS: Pressure suppression systemQT: Quench tankRC: Reactor cavityRELAP: REactor loss of coolant analysis programRPV: Reactor pressure vesselRV: Reactor vesselRWST: Refueling water storage tankR&D: Research and developmentSB: Small breakSET: Separate effect testsSIET: Societa Informazioni Esperienze
Termoidrauliche (company for informationand experiences on thermal-hydraulics)
SG: Steam generatorSL: Steam lineSMR: Small and medium-sized reactorSPES: Simulatore pressurizzato per esperienze di
sicurezza (pressurized simulator for safety tests)ST: Single traintempf: (TEMPF) liquid temperature (RELAP5
variable)WEC: Westinghouse Electric Company LLC.
References
[1] M. D. Carelli, L. E. Conway, L. Oriani et al., “The design andsafety features of the IRIS reactor,” Nuclear Engineering andDesign, vol. 230, no. 1–3, pp. 151–167, 2004.
[2] M. D. Carelli, B. Petrovic, L. E. Conway et al., “IRIS designoverview and status update,” in Proceedings of the 13th
International Conference on Nuclear Engineering (ICONE13-50442 ’05), Beijing, China, May 2005.
[3] B. Petrovic, M. D. Carelli, and N. Cavlina, “IRIS—international reactor innovative and secure: progress in devel-opment, licensing and deployment activities,” in Proceedings ofthe 6th International Conference on Nuclear Option in Coun-tries with Small and Medium Electricity Grids, Dubrovnik,Croatia, May 2006.
[4] M. D. Carelli, B. Petrovic, M. Dzodzo et al., “SPES-3experimental facility design for IRIS reactor integral testing,”in Proceedings of the European Nuclear Conference (ENC ’07),Brussels, Belgium, September 2007.
[5] M. Carelli, L. Conway, M. Dzodzo et al., “The SPES3experimental facility design for the IRIS Reactor simulation,”Science and Technology of Nuclear Installations, vol. 2009,Article ID 579430, 12 pages, 2009.
[6] R. Ferri, A. Achilli, C. Congiu et al., “SPES3 facility and IRISreactor numerical simulations for the SPES3 final design,” inProceedings of the European Nuclear Conference (ENC ’10),Barcelona, Spain, May June 2010.
[7] T. K. Larson, F. J. Moody, G. E. Wilson et al., “Iris small breakloca phenomena identification and ranking table (PIRT),”Nuclear Engineering and Design, vol. 237, no. 6, pp. 618–626,2007.
[8] IAEA-TECDOC 1536, “Status of small reactor designs withouton-site refuelling (IAEA ’07),” 2007.
[9] R. Ferri and C. Congiu, SPES3-IRIS facility nodalization forRELAP5 Mod.3.3 code and steady state qualification. SIET 01423 RT 08 Rev.0, ENEA FPN-P9LU-017, 2009.
[10] R. Ferri and C. Congiu, SPES3-IRIS facility RELAP5 base casetransient analyses for design support. SIET 01 489 RT 09Rev.0., ENEA FPN-P9LU-035, 2009.
[11] R. Ferri and C. Congiu, SPES3-IRIS facility RELAP5 sensitivityanalyses of the Lower Break transient for design support. SIET01 499 RT 09 Rev.0., FPN- P9LU-040, 2009.
[12] R. Ferri, SPES3-IRIS facility RELAP5 sensitivity analyses onthe containment system for design review. SIET 01 526 RT 09Rev.0., ENEA NNFISS-LP2-017, 2010.
[13] R. Ferri and P. Meloni, Approach for a correct simulation ofthe SPES3-IRIS Emergency Heat Removal System with theRELAP5/MOD3 Code. SIET 01 745 RT 11 Rev.0. Piacenza,Italy, 2011.
[14] RELAP5 code manual. NUREG/CR-5535/Rev.1 Idaho Nation-al Engineering Laboratory (USA), 2001.
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