Experiences of TRAC-P code at INS/NUPEC · 2002. 7. 16. · Experiences of TRAC-P code at INS/NUPEC...

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Experiences of TRAC-P code

at INS/NUPEC

Fumio KASAHARA(E-mail : kasahara@nupec or jp)

Institute of Nuclear Safety (INS)Nuclear Power Engineering Corporation (NUPEC)

Exploratory Meeting of Experts on BE Calculations and Uncertainty Analysisin Aix en Provence, May 13-14, 2002

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Contents

1. Preparation of the input data with Fine noding model

2. Large break LOCA analysis by Fine noding model

3. Uncertainty Methods Study by Coarse noding model

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(1) Noding

We have been prepared the system analysis noding ofJapanese 4-loop PWR.

It is constituted from 3-D VESSEL and 4 primary coolantloops.

And based on the RELAP5 code input data that we usefor the demonstration analysis.

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Fig.1 4-Loop PWR Fine Noding(81)

(50)

(11)(51)

(52)

(12)

(10)

(13) (14) (15)

(85)

(16)

(70)

(83)

J47 J50

J49

J48

J2J3J1

J6J28J5

J4

J31

J29

J27

J30

J58J55

J57

J56

J15 J14

J17 J38 J18

J13

J40

J37J41

J39

J16

(56)(58)

(57)(31)

(30)

(33)(32)

(34) (35)

(72)

(36)

(87)

(40)

Loop 1

Loop 3

Loop 2

Loop 4

(44)(45)J63 J64 (43)

(42)

(47)

(46)

(73)

(48)

(89)

(88)

(60)(41)

(59)

(84)

(61)

J19

J63

J45

J42

J44

J46

J22

J21J20

J60

J23

J43

J59

J61

J62

J24

J34

J32 J36

J33J12 J11

J10J35

J8 J9

J52

J26

J25J7

J51

J53

(82)

(53)

(21) (54)

(55)(80)

(2)

(20)

(22)(24) (23)(25)

(86)(71)

(26)

(1)

(27)

(90)

(17)

(37)

(N) : Com ponent No.Jn : Junction No.

(Broken Loop)

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Fig.2 Reactor Vessel Fine Noding

Loop 1

Loop 4(Broken Loop)

Loop 3

Loop 2

Level 17

Level 4

Level 1

Level 11

Buffle-BarrelRegion

Guide Tube

(2) Detailed model of in-vessel structures

Include core buffle-barrelregion and reactor control rodguide tubes.

HTSTRs are modeled toconserve their volume andheat transfer area.

Based on the drawings lentfrom the electric company, soinput data are confidential.

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Fig.3 ECCS Injection FlowTable Input

(3) Other reactor coolant systemcomponents

Pressurizer and accumu-latorsare modeled by PIPEcomponents.

ECCS low pressure injec-tionflow is modeled by FILLcomponent. (Fig.3)

This table is applied to eachintact cold legs.

0

50

100

150

0.0 0.2 0.4 0.6 0.8 1.0

pressure (M Pa)mass flow (kg/s/loop)

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Fig.4 CV Pressure Table Input(4) Containment vessel

Containment vessel free volumeis not modeled.

Containment vessel pres-sure ismodeled by BREAK component.(Fig.4)

This table is based on the reactorestablishment permit report.

Pressure increases linearly to0.26 MPa by 15 s

0

0.1

0.2

0.3

0 50 100 150 200 250

tim e (s)

pressure (MPa)

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Fig.5 Core Power Table Input(5) Reactor power

Reactor core power is modeledby time table. (Fig.5)

It is stepped down to 7% ofinitial power.

It includes decay heat of ANS-1979 plus 2 sigma. 0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250

tim e (s)

power ratio

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(1) Noding and boundary conditions

Fine noding model and boundary conditions are used

Figure 1 to 5 show these analysis model

Power distribution is defined by Average-power Rod (AVRod)

Hot rod is modeled by Additional Supplemental Rod (ASRod)

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(2) Description of Fine noding model

guillotineBreak shape

loop 4 RCP dischargeBreak point

34.7*1.22=42.3, equivalent toFQ=1.31*1.45*1.22=2.32

42.3AS Rod max linear power density(kW/m)

3,411/50,952/3.66*1.31*1.45=0.034734.7AV Rod max linear power density(kW/m)

25 points input based on cosine-shapedistribution

1.45z-direction max power ratio

ring average of cosine-shape distribution1.31r-direction max power ratio

3,411Initial reactor power (MWt)

3*4*8Core sell division (r, t, z)

5*4*17VESSEL cell division (r, t, z)

nhtstr35Number of HTSTRs

ncomp107Number of Components

NoteValueItem

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(3) Result of transient analysis

1,074 KPCT 3rd peak appeared99

timer delayed operationECCS injection started39

1,100 KPCT 2nd peak appeared38

judged by the flow direction at core bottomReflood phase started33

set pressure at 4.5 MPaAccumulator injectionstarted

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1,120 KPCT 1st peak appeared4

Assumption, reactor power step down to 7% by 0.1 s,followed by decay heat of ANS(1979)+2 sigma

reactor stop0

Assumption, flow coastdown by Semiscale test facilitypump characteristics

loss of electrical power toRCPs

0

after 1,000 s Null Transientbreak0

noteeventtime (s)

a. Chronology

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(3) Result of transient analysisb. Core pressure

0

5

10

15

20

0 50 100 150 200 250

tim e (s)

pressure (MPa)

Fig.6 Core Pressure

Decreases to the CV pressure setas boundary condition about 30s

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(3) Result of transient analysisc. Core void fraction

Fig.7 Core Void Fraction

Increases to 1.0 from 0.0instantly after the breakinitiation, and continues athigh value about 0.9

0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250

tim e (s)

core center void fraction

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(3) Result of transient analysisd. Maximum hot rod surface temperature

Fig.8 M axim um Hot RodSurface TemperatureIncreases to 1,120K from

600K at about 4s.

Reflood phase begins at about33s and the second peak of1,100K appears at 38s.

The third peak of 1,074Kappears at about 99s.

400

600

800

1000

1200

0 50 100 150 200 250

tim e (s)

temperature (K)

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(1) Trial of GRS type Ordering Statistics

Evaluation parameter is maximum hot rod surfacetemperature during large break LOCA blowdown phase.

Two parameters are selected as cause parameter. (dischargecoefficient CD and power peaking factor Q)

Based on the Wilk’s formula, we can obtain the uppertolerance limit (UTL) at 95% probability on 95% confidencelevel.

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(2) Noding

This noding model is prepared by US NRC for test problemof US 4-loop PWR.

There are two hot legs and steam-generators.

One of them represents intact loops and is 3-loop-size.

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Fig.9 4-Loop PWR Coarse Noding


(26)

(24) (22)

(23)

(18) (28)

(12)(11)

(10)

(19)

(13)

(14) (15)

(25)(20)

(31)

(21)

(27)

(9)

(17)

(8)

(3)(2)

(1)

(4)

(5)

(6)

(7)

(16)

Loop 2 (3-loop size)

Loop 1(Broken Loop)

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Fig.10 Reactor Vessel Coarse Noding


Level 1

Level 7

Level 5

Level 3

Loop 1

(Broken Loop)

Loop 2

Loop 3 Loop 4

Core region is consist of

Three axial noding,

Four azimuthal noding, but

No radius noding.

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(3) Description of Coarse noding model

150% splitBreak shape

loop 4 RCP dischargeBreak point

27.9 x 1.1=30.7, equivalent toFQ=1.23*1.1=1.35

30.7AS Rod max linear power density (kW/m)

3,250/39,372/3.64 x 1.23=0.027927.9AV Rod max linear power density(kW/m)

4 points input for distribution1.23z-direction max power ratio

3,250Initial reactor power (MWt)

1*4*3Core sell division (r, t, z)

2*4*7VESSEL sell division (r, t, z)

nhtstr15Number of HTSTRs

ncomp48Number of Components

NoteValueItem

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(4) Cause parameters

0 5 10 15 20 25 30

1.012

1.034

1.056

1.078

1.100

1.122

1.144

1.166

1.188

rank of Q

frequency

0 5 10 15 20 25 30

0.80

0.84

0.88

0.92

0.96

1.00

1.04

1.08

1.12

1.16

1.20

rank of CD

frequency

Power peaking factor Q of 124 random samples : normal distribution, myu=1.1, sigma=0.044

Discharge Coefficient CD of 124 random samples : uniform distribution, min=0.8, max=1.2

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(5) Typical maximum rod surface temperatureBy different Q=1.0, 1.1, 1.2, and fixed CD=1.0

By different CD=0.8, 1.0, 1.2, and fixed Q=1.1

Maximum value of each curve is “blowdown peak”.

500

600

700

800

900

0 1 2 3 4 5 6

tim e (s)

temperature (K)

Q =1.2Q=1.1

Q=1.0

500

600

700

800

900

0 1 2 3 4 5 6

tim e (s)

temperature (K)

CD =1.2

CD=1.0

CD=0.8

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(6) Discussion of blowdown peaksBlowdown peaks based on random Q and CD

Both figures are arranged from the same results of 124 cases.

500

600

700

800

900

0.9 1.0 1.1 1.2 1.3

peaking factor Q

temperature (K)

a. Arrangement by QThis distribution showswidely spread and smallpositive correlation.

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b. Arrangement by CD

This distribution showsobvious positive correlationfocusing to about 830K withabout 50K spread.

500

600

700

800

900

0.6 0.8 1.0 1.2 1.4

discharge coefficient CDtemperature (K)

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c. 95-95 upper tolerance limit based on Wilk’s formula

These values are equivalent as Upper Tolerance Limit of 95%probability on 95% confidential level based on the Wilk’sformula.

855 K3rd max of 124 samples124856 K2nd max of 93 samples93863 K1st max of 59 samples59

value95%*95% UTLNumber ofsamples

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(7) Conclusion and future plan

We have made prototype of GRS-type uncertainty evaluationsystem.

We will select several ten pieces of cause parameter,

And modify the TRAC-P code to handle those parameters by“tracin”,

And apply this uncertainty evaluation system to evaluate threepeaks of large break LOCA PCT using fine noding model.

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Experiences of TRAC-P code at INS/NUPEC · 2002. 7. 16. · Experiences of TRAC-P code at INS/NUPEC...

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