conclusions from quench-03 test analyses with icare2 and melcor codes

Conclusions from Quench-03 Test Analyses with ICARE2 and MELCOR CodesJi Duspiva

Nuclear Research Institute e, plc.Nuclear Power and Safety DivisionDept. of Reactor Technology

11th International QUENCH WorkshopKarlsruhe, Germany, October 25-27, 2005

11th International QUENCH Workshop Karlsruhe, Germany, October 25-27, 2005

Outline

Background of Quench analysis in NRI eQuench-03 test analysis with ICARE2 (Short summary of 10th QWS presentation)Comparison to MELCOR 1.8.5Improved model of Quench-03Comparison to MELCOR 1.8.5Regressive application to Quench-01Summary and conclusions


Backgroundof NRI Quench AnalysesFirst NRI Quench activities were performed with MELCOR CodeOwn MELCOR input model was developed for Quench-01 [1], successfully also applied to Quench-06 [ISP-45 Blind phase] calculationsQuench-03 Calculation was last with MELCOR 1.8.5 [2]Temperature at onset of reflooding higher than Q-01 and Q-06Temperature escalation was not predicted correctlyStrong underestimation of Hydrogen productionUnder EU Project SARNET in TPA1/JPA1 (WP9: Early Phase of Core Degradation ST-1 Hydrogen Generation during Core Reflooding) started application of ICARE2 Code with following schedule [3] and [4]Step 1 Preparation of model and calculation of Quench-01 testStep 2 - Sensitivity Study on the change of important parametersStep 3 Calculation of Quench-03 test

[1] J. Duspiva: Quench-01 Test Calculation with MELCOR Code, CSARP Meeting, May 7-9, 2001, Bethesda, Maryland [2] J. Duspiva: Quench-03 Test Calculation with MELCOR Code, 8th International Quench Workshop, Karlsruhe, Germany, October 29-31, 2002[3] J. Duspiva: Quench Test Calculations with ICARE2 Code and Comparison with MELCOR Code Results, 10th International Quench Workshop, Karlsruhe, Germany, October 26-28, 2004[4] J. Duspiva: Quench Test Calculations with ICARE2 Code and Comparison with MELCOR Code Results (Quench-01 and Quench-03 Test Analyses), Report NRI e, UJV-12204-T, March 2005


ICARE2 Input ModelQuench Facility NodalizationOriginal model, received from L. Belovsky (ALIAS CZ), was prepared by G. Bandini (ENEA)MacrocomponentsUnheated rod8 heated rods of inner ring12 heated rods of outer ring3 Corner rods (withdrawal of one corner rod neglected) Grid spacers andShroud with gap above heated zoneOne TH channel FLUID2 type41 axial levels4 below heated part21 in heated part16 upper plenumFirst test on Quench-01 Sensitivity Matrix Improvements


1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

GRIDL2

-0.2

-0.3

-0.4

GRIDL3

-0.47

CLAD1

PZO1

PZO2

MO2B

IE2B

CLAD2

TUNG2

MO2A

IE2A

CU2A

MO3A

IE3A

CU3A

TUNG3

CLAD3

IE3B

MO3B

PZO3

BZIRR

BZIR

BSS

BZF5

BZF4

BZF3

BZF2

BZF1

Central Unheated Rod

Inner Heated Ring Rod

Outer Heated Ring Rod

Shroud Wall

Ax.L. 41

Ax.L. 40

Ax.L. 39

Ax.L. 38

Ax.L. 37

Ax.L. 36

Ax.L. 35

Ax.L. 34

Ax.L. 33

Ax.L. 32

Ax.L. 31

Ax.L. 30

Ax.L. 29

Ax.L. 28

Ax.L. 27

Ax.L. 26

Ax.L. 25

Ax.L. 24

Ax.L. 23

Ax.L. 22

Ax.L. 21

Ax.L. 20

Ax.L. 19

Ax.L. 18

Ax.L. 17

Ax.L. 16

Ax.L. 15

Ax.L. 14

GRIDU1

Ax.L. 13

GRIDU2

GRIDM1

Ax.L. 12

GRIDM2

Ax.L. 11

GRIDM3

Ax.L. 10

Ax.L. 9

Ax.L. 8

Ax.L. 7

Ax.L. 6

Ax.L. 5

Ax.L. 4

Ax.L. 3

Ax.L. 2

GRIDL1

Ax.L. 1

-0.1

Bundle, Shroud & Central Rod Axis

Inner Ring Rod Axis

Outer Ring Rod Axis

Elevation [m]

GRIDU3

GRIDB1

GRIDL3

GRIDL2

Quench-01Results of Reference CalculationTotal Hydrogen production predicted correctly tuned up by external resistivityTemperature profiles also predicted well until the beginning of refloodingHeat Balance was checked, based on methodology from ISP-45


Quench-03Input File ChangesChanges done in comparison with Quench-01 calculation (identical approach as in MELCOR analyses of Quench-01 and Quench-03 tests)

Redefinition of (initial and boundary conditions)Power per ringInlet temperatures and mass flow rates (Ar, steam and water)Initial temperatures in bundleTime of reflooding beginningTimestep definition


Quench-03Hydrogen ProductionFirst step in the input modifications was done in tuning up of external resistivity temperature instability in bottom part of bundleTuned up external resistivity 2.1 m/rod

Quench-01 like external resistivity 3.09 m/rod


Quench-03Temperature Profile at 2600 sQuench-01 like external resistivity 3.09 m/rod

Tuned up external resistivity 2.1 m/rod

Water injection onset at 2600 s


ICARE2 to MELCOR Comparison

Similar behaviour of both analyses for H2 production when all settings from Q-01 are applied in Q-03 (change of initial and boundary conditions)Also temperature evolutions had a lot of similaritiesRelatively good agreement of temperature prediction in lower and middle part of heated zoneNo temperature escalation results in underestimation of H2 production[2] J. Duspiva: Quench-03 Test Calculation with MELCOR Code, 8th International QUENCH Workshop, Karslruhe October 29-31, 2002End of 10th QWS 2004 NRI Contribution Summary


Identification of Critical PointApplication of ATLAS Postprocessor At 2600 sSignificant underprediction of temperatures in hot zoneFrom analyst point of view identified as overestimation of heat losses through shroud in area of hot zoneFrom Q-03 test point of view identified as loss of heat removalGRS postprocessor ATLASICARE2 results reprocessing by MELCOR


Modelling Approach Used

More possible ways existDefinition of material properties was separated forBZF2-5BZF1 Conductivity of solid material was modified for temperature above 550 KFinal values were defined iteratively based on temperature profiles at onset


1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

GRIDL2

-0.2

-0.3

-0.4

GRIDL3

-0.47

CLAD1

PZO1

PZO2

MO2B

IE2B

CLAD2

TUNG2

MO2A

IE2A

CU2A

MO3A

IE3A

CU3A

TUNG3

CLAD3

IE3B

MO3B

PZO3

BZIRR

BZIR

BSS

BZF5

BZF4

BZF3

BZF2

BZF1

Central Unheated Rod

Inner Heated Ring Rod

Outer Heated Ring Rod

Shroud Wall

Ax.L. 41

Ax.L. 40

Ax.L. 39

Ax.L. 38

Ax.L. 37

Ax.L. 36

Ax.L. 35

Ax.L. 34

Ax.L. 33

Ax.L. 32

Ax.L. 31

Ax.L. 30

Ax.L. 29

Ax.L. 28

Ax.L. 27

Ax.L. 26

Ax.L. 25

Ax.L. 24

Ax.L. 23

Ax.L. 22

Ax.L. 21

Ax.L. 20

Ax.L. 19

Ax.L. 18

Ax.L. 17

Ax.L. 16

Ax.L. 15

950 K

Ax.L. 14

GRIDU1

Ax.L. 13

GRIDU2

GRIDM1

Ax.L. 12

GRIDM2

Ax.L. 11

GRIDM3

Ax.L. 10

Ax.L. 9

Ax.L. 8

Ax.L. 7

Ax.L. 6

Ax.L. 5

Ax.L. 4

Ax.L. 3

Ax.L. 2

GRIDL1

Ax.L. 1

-0.1

Bundle, Shroud & Central Rod Axis

Inner Ring Rod Axis

Outer Ring Rod Axis

Elevation [m]

GRIDU3

GRIDB1

GRIDL3

GRIDL2

550 K

610 K Q-01

Q-01 and Q-03

600 K Q-03

Improved PredictionTemperature Profile at ______Temperature profiles are in agreement with measured valuesSignificantly lower temperature of Zirconia fiber layersAll three types of rod are degraded, shroud remains intact Visualization 2500 s 2520 s 2540 s 2560 s 2580 s 2590 s 2600 s 2610 s 2620 s 2630 s 2640 s 2650 s 2660 s 2670 s 2680 s 2690 s 2699 sReflooding phase observationsOverprediction of temperatures in bottom partOscillations of swollen water levelQuench front level remains at bottomContinuation of calculation is problematic due to unconvergency and too small timestep (< 10-4 s)Calculation of whole Q-03 was not finished and is not planned 2710 s


Application of New ZF Propertiesto MELCOR AnalysisIdentical figure of temperature profiles with modified ZrO2 Fiber Conductivity At 2600 sSignificant reduction of ZF temperatures as in ICARE2 runSlightly underpredicted temperatures of hot zoneH2 production underpedicted 22 gReason trick in shroud modelling to allow its oxidation


Bundle Refloodingin MELCOR Analysis At 2725 sReflooding phase observationsCorrect prediction of water level Agreement in temperature drop due to quenchingRod and shroud degradations are not predicted so intensive as in ICARE2 runCode stability no termination of run


Summary and Conclusions

Application of new postprocessing (using GRS ATLAS tool via MELCOR code) made a possible to identified cause of modelling troublesThree screens prepared one of them for both of codes used direct comparisonWorking term of phenomenon identified: loss of heat removal through shroud in hot zoneModelling of this feature was done by changing of Zirconia fiber conductivityImproved modelling resulted in very good agreement in temperature profiles at the time of water injection onset in ICARE2 analysis In MELCOR analysis - agreement was not found, but temperature profiles were improved too trick in shroud oxidation modelling with fixed heat transfer coefficient (COR00011 input row)ICARE2 calculation of reflooding phase results in unconvergency and timestep reduction, oscillation in swollen water level occurred MELCOR run was more stable during reflooding phase


Summary and Conclusions

Application of ICARE2 code allowed to identify cause, which was not possible to identify with integral code due to its modelling simplifications, but conclusions are relevant to both of codes (new features of MELCOR1.8.6 will allow more direct validation on Quench tests)Regressive application of Zirconia fiber properties to Quench-01 analysis with ICARE2 code resulted in strong overpediction of temperatures and hydrogen productionPhenomenon occurred in Quench-03 test only, not in Quench-01, so it is not possible to use the same model for analysis of both testsFinal identification and description of phenomenon, which occurred in Quench-03, should be done by experimenters from FZK, only one of possible analytical approaches to model this test was presentedSpecificity of Quench-03 results from shroud behaviour Not objective of Quench programUnimportant for plant applications no another analysis are neededOutput from effort is available in Report UJV-12204-T (2)


Nuclear Research Institute e, plc.Nuclear Research Institute e, plc.Nuclear Research Institute e, plc.

conclusions from quench-03 test analyses with icare2 and melcor codes

Documents

calculation of quench

quench test calculations

melcor code results

improved model of quench

test analyses

test analysis

application of icare2

heated part21