17th Symposium of AER, Yalta, Crimea, Ukraine, Sept. 24-29, 2007.

17th Symposium of AER, Yalta, Crimea, Ukraine, Sept. 24-29, 2007

Advanced Analysis of the CEA-NEA/OECD VVER-1000 Coolant Transient Benchmark with the Coupled System Code ATHLET/BIPR-VVER

S. Nikonov 1, M. Lizorkin1, S. Langenbuch2, K. Velkov2

1 RRC KI, 123182 Moscow, Russia 2 GRS mbH, 85748 Garching, Germany


CONTENT

Introduction

ATHLET/BIPR-VVER reactor pressure vessel model

- mixing at assembly head

Exercise 1 of Phase 2 of the CEA-NEA/OECD VVER-1000 Coolant Transient Benchmark

Thermocouple correlation

Further developments

Summary


INTRODUCTION

The nodalization of the RPV and a correct description of the mixing phenomena in the RPV plays a very big role on the accuracy of the predicted local core parameters which are needed to check the acceptance critera.

Recent studies proved that additional modelling of the assembly outlets by the coupled code ATHLET/BIPR-VVER is necessary in order to take into account the fluid mixing phenomena at the thermocouple location

Correlation based on measured thermal-couples‘ values at core outlet (for VVER-1000) with the real coolant temperatures at those positions are necessary for correct comparison

In order to meet all these additional requirements, new models have been included in the coupled code ATHLET/BIPR-VVER and an international Benchmark problem based on experimental data is recalculated


NODALIZATION OF THE REACTOR VESSEL (OPTIMAL nodalization schema)

16 down comers modelled with 16 parallel thermal-hydraulic channels (PTHC) with cross flows (CF).

• 16x7= 112 bottom plenums (2 levels) modelled with 118 PTHCs with CFs which describe the volume of the reactor bottom part with the perforated elliptical bottom plate up to the fuel assembly support plate

163 + 163 = 326 PTHC in the core (2:1) – 2 PTHC per assembly

– 163 for the assembly flow

– 163 for the control rod guide tube flow

3 different types of guide tube channels

– Empty

– Burnable absorbers

– Control rods

DW_CAM-001DW_CAM-010


158(14) 159(14) 160(14) 161(14) 162(14) 163(14)

149(15) 150( 0) 151( 3) 152( 0) 153( 9) 154( 0) 155( 4) 156( 0) 157(13)

139(15) 140( 4) 141( 0) 142( 7) 143( 1) 144( 2) 145( 8) 146( 0) 147( 3) 148(13)

128(15) 129( 0) 130( 8) 131( 0) 132( 0) 133( 5) 134( 0) 135( 0) 136( 7) 137( 0) 138(13)

116(15) 117( 9) 118( 2) 119( 0) 120(10) 121( 0) 122( 0) 123(10) 124( 0) 125( 1) 126( 9) 127(13)

103(15) 104( 0) 105( 1) 106( 6) 107( 0) 108( 0) 109( 6) 110( 0) 111( 0) 112( 6) 113( 2) 114( 0) 115(13)

89(15) 90( 3) 91( 7) 92( 0) 93( 0) 94( 6) 95( 0) 96( 0) 97( 6) 98( 0) 99( 0) 100( 8) 101( 4) 102(13)

76( 0) 77( 0) 78( 0) 79(10) 80( 0) 81( 0) 82( 5) 83( 0) 84( 0) 85(10) 86( 0) 87( 0) 88( 0)

62(16) 63( 4) 64( 8) 65( 0) 66( 0) 67( 6) 68( 0) 69( 0) 70( 6) 71( 0) 72( 0) 73( 7) 74( 3) 75(12)

49(16) 50( 0) 51( 2) 52( 5) 53( 0) 54( 0) 55( 6) 56( 0) 57( 0) 58( 5) 59( 1) 60( 0) 61(12)

37(16) 38( 9) 39( 1) 40( 0) 41(10) 42( 0) 43( 0) 44(10) 45( 0) 46( 2) 47( 9) 48(12)

26(16) 27( 0) 28( 7) 29( 0) 30( 0) 31( 6) 32( 0) 33( 0) 34( 8) 35( 0) 36(12)

16(16) 17( 3) 18( 0) 19( 8) 20( 2) 21( 1) 22( 7) 23( 0) 24( 4) 25(12)

7(16) 8( 0) 9( 4) 10( 0) 11( 9) 12( 0) 13( 3) 14( 0) 15(12)

1(11) 2(11) 3(11) 4(11) 5(11) 6(11) (0) – empty guide tubes;

(1-10) – control rod group numbers;

(11-16) – burnable absorbers.

Location of the different types of guide tube channels in the core


48 bypass THC

24 axial nodes in the active core

2 upper plenums and 1 reactor head

163 +163 = 326 heat structures (HS) in the core

– 163 HS for the fuel assemblies

– 163 HS for the guide tubes

Neutronically the core is modelled 1:1 (1 node per assembly in X-Y plane)

All other details concerning nodalization and modelling of the primary and secondary loop can be seen in:

S. Nikonov, Lizorkin M., Kotsarev A., Langenbuch S., Velkov K., Optimal Nodalization Schemas of VVER-1000 Reactor Pressure Vessel for the Coupled Code ATHLET-BIPR8KN, 16th Symposium of AER, Bratislava, September 2006.


TRANSIENT: Isolation (closure of SIV-1 and FW valve)Isolation (closure of SIV-1 and FW valve) of SG-1 of SG-1 at reactor power of 9.36% Pnom of 9.36% Pnom (Benchmark V1000CT – Phase 2, Exersice 1)

Comparison of the cold and hot legs’ temperature agree very well with the measurements. The maximum differences are 1.8 K. These differences are small considering the reported measurements’ error of 2.0 K.

The differences in the predicted local coolant temperatures at the begin and at the end of the transient compared with the measured one are small. At t=0 s the maximum assembly coolant temperature deviation is 1.4 K, and at the end of the transient – 5.8 K.


COMPARISON OF COLD LEG 1 TEMPERATURE HISTORIES

540,0

542,0

544,0

546,0

548,0

550,0

552,0

554,0

556,0

558,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED

COMPARISON OF HOT LEG 1 TEMPERATURE HISTORIES

544,0

546,0

548,0

550,0

552,0

554,0

556,0

558,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED


541,0

541,5

542,0

542,5

543,0

543,5

544,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED


544,0

544,5

545,0

545,5

546,0

546,5

547,0

547,5

548,0

548,5

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED

COMPARISON WITH MEASUREMENTS – LOOPS‘ COOLANT TEMPERATURES

Loop #1

Loop #2



541,0

541,2

541,4

541,6

541,8

542,0

542,2

542,4

542,6

542,8

543,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED


544,0

544,5

545,0

545,5

546,0

546,5

547,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED


541,0

541,2

541,4

541,6

541,8

542,0

542,2

542,4

542,6

542,8

543,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E,

K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED


544,5

545,0

545,5

546,0

546,5

547,0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E, K

6 DC

16 DC

24 DC

34 DC

48 DC

MEASURED

Loop #3

Loop #4


OUTLET COOLANT TEMPERATURE AT ASSEMBLY #64

270

272

274

276

278

280

282

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E [

C]

ASSEMBLY

G. TUBE


270

271

272

273

274

275

276

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E [

C]

ASSEMBLY

G. TUBE


269

270

271

272

273

274

275

276

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E [

C]

ASSEMBLY

G. TUBE


270

270,5

271

271,5

272

272,5

273

273,5

274

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E [

C]

ASSEMBLY

G. TUBE

Comparison of outlet coolant temperature histories for different types of assemblies with different guide tube channel usage


Mean(oC)

Max(oC)

Min(oC)

Max -Min(oC)

MaximumDeviation (oC)(Assembly #)

MinimumDeviation (oC)(Assembly #)

SIGMA

Experiment 275.08 285.50 270.40 15.10

Assemblies 275.86 288.26 271.00 17.26 6.40 ( 51) -3.49 ( 31) 4.0259

Guide tubes 275.06 286.97 270.35 16.62 5.69 ( 51) -4.12 ( 31) 3.4922

10% mixing 275.13 287.09 270.41 16.68 5.75 ( 51) -4.06 ( 31) 3.4809

20% mixing 275.19 287.19 270.46 16.73 5.80 ( 51) -4.02 ( 31) 3.4805

30% mixing 275.24 287.27 270.50 16.76 5.85 ( 51) -3.98 ( 31) 3.4867

40% mixing 275.29 287.34 270.54 16.80 5.89 ( 51) -3.94 ( 31) 3.4968

50% mixing 275.33 287.40 270.57 16.83 5.92 ( 51) -3.91 ( 31) 3.5091

60% mixing 275.36 287.45 270.60 16.85 5.95 ( 51) -3.88 ( 31) 3.5225

70% mixing 275.39 287.50 270.63 16.80 5.98 ( 51) -3.86 ( 31) 3.5364

80% mixing 275.41 287.54 270.65 16.90 6.00 ( 51) -3.84 ( 31) 3.5505

Comparison of different flow mixing relations on the model accuracy for the end of the experiment


THERMOCOUPLE CORRELATION (interpretation of the TC measurements)

TTC = (TGT + CM * TASS ) / ( 1 + CM)

TTC - thermocouple temperature

TGT - guide tube coolant flow temperature

TASS - fuel assembly coolant flow temperature

CM - mixing coefficient (0.2)


FURTHER DEVELOPMENTS

Confirmation of the TC correlation for nominal and intermediate reactor power (in preparation )

The TC correlation is derived from

data set with a heat up of only 3 oC

and reactor power of 9.4 % Pnom

Dependence of the mixing coefficient at assembly head from the type of the guide tube application (empty, inserted rods, CRs insertion depth, burnable absorbers)

Study the influence of different coolant temperature in the guide tubes on the accuracy of the microscopic cross section generation and homogenization procedures

COOLANT TEMPERATURE AT THC #89

268

269

270

271

272

273

274

0 200 400 600 800 1000 1200 1400 1600 1800 2000

TIME [S]

TE

MP

ER

AT

UR

E[C

]

INLET

OUTLET


SUMMARY

A method is developed which allows to take into account the correct interpretation of the TC measurements (still subjected to validation)

Additional modelling in the coupled code ATHLET/BIPR-VVER is developed to meet the requirements of the correct description of the fluid mixing phenomena at the places where the TCs are located (additional PTHC introduced)

The Exercises of Phase 2 of the CEA-NEA/OECD VVER-1000 Coolant Transient are recalculated introducing the new TC correlation and the data are compared with the old ones

The coupled system code ATHLET/BIPR-VVER is able to predict the coolant temperature at the assembly outlet within a rather high accuracy even though ATHLET system code is based on 1-D thermal-hydraulic pipe models

17th Symposium of AER, Yalta, Crimea, Ukraine, Sept. 24-29, 2007.

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Transcript of 17th Symposium of AER, Yalta, Crimea, Ukraine, Sept. 24-29, 2007.