ERMSAR 2012, Cologne, March 21-23, 2012
Overview of the ASTEC V2.0-rev1 validation
P. Chatelard (IRSN), S. Arndt (GRS), B. Atanasova (INRNE)
G. Bandini (ENEA), A. Bleyer (IRSN), T. Brähler (RUB)
M. Buck (IKE), I. Kljenak (JSI), B. Kujal (UJV)
ERMSAR 2012, Cologne, March 21-23, 2012 2
Introduction to the ASTEC validation strategy
Examples of the assessment of some ASTEC V2.0-rev1 modules by SARNET partners
– Core degradation module
– Containment module
– MCCI module
Summary of the ASTEC V2.0-rev1 assessment
Conclusion and perspectives
Contents
ERMSAR 2012, Cologne, March 21-23, 2012 3
ASTECcontext and objectives
IRSN-GRS cooperation since 1996 for development of an integral codeASTEC (Accident Source Term Evaluation Code) for present/future nuclear water-
cooled reactors (PWR, BWR, VVER, CANDU) source term severe accident calculation, from initiating event until radioactive release out of the containment:
– Evaluation of source term
– PSA level 2 studies (PSA-2)
– SA management (SAM) evaluation
– Support of experimental programmes
Progressive evolution in recent years towards a state-of-the-art tool for source term calculations:
– Most modeling is mechanistic, only sometimes simplified– Repository of knowledge of severe accident phenomenology
ASTEC = Reference European code in the SARNET network
New series of ASTEC versions (V2 series) since 2009– Mid-2009 : V2.0 First V2 validation by several partners (SARNET2 1st
period) – Mid-2010 : V2.0-rev1 Extended V2 validation by number of partners (SARNET2 2nd period) – End-2011 : V2.0-rev2 Validation to be continued in the frame of SARNET2 3rd period
ERMSAR 2012, Cologne, March 21-23, 2012 4
ASTEC V2A new series of versions (1/2)
ERMSAR 2012, Cologne, March 21-23, 2012 5
ASTEC V2.0-rev1validation strategy
Three-tier validation approach (made possible since ASTEC is very modular)– Separate-Effect-Tests focusing on only 1 physical phenomenon– Coupled-Effect-Tests focusing on a set of physical phenomena– Integral tests to check the coupling of physical models and that no essential phenomenon was
forgotten or neglected
Very large ASTEC V2 validation matrix covering all SA phenomena and including major (past, on-going) French, German and international exp. Programs (including VVER experiments), such as in particular:
– All Phebus FP experiments;– Many ISPs: 27 (BETHSY), 33 (PACTEL), 31-36 (CORA), 34 (FALCON), 35 (NUPEC), 37 (VANAM),
39 (FARO), 40 (STORM), 41 (ACE-RTF, CAIMAN), 44 (KAEVER), 45 (QUENCH-06), 46 (Phébus-FPT1), 47 (TOSQAN-MISTRA-ThAI), 49 (ThAI-Enaceff);
– OECD projects: LHF-OLHF, RASPLAV/MASCA, OECD-CCI;– Circuit experiments: BETHSY, ROSA, PACTEL, LOFT-FP, … as well as the TMI-2 scenario – On-going and future new experiments: LIVE on corium pools, PRELUDE, DEBRIS & PEARL on
reflooding, DISCO on DCH, ThAI on containment, EPICUR, CHIP & THAI on iodine, RUSET on ruthenium, VULCANO on MCCI…
The multi-partners validation of ASTEC V2.0-rev1 revision is briefly illustrated in the following through few calculation examples
3 different ASTEC modules have been selected for that purpose
ERMSAR 2012, Cologne, March 21-23, 2012 6
Example of core degradation module assessmentPhébus FP bundle experiments
Phébus FPT3 (work performed by ENEA)
Reasonable agreement on thermal behaviour as well as on both oxidation and relocation processes using the new ICARE 2D magma relocation model which is the one recommended by IRSN for plant applications
Bundle temperature at 0.6 m Total hydrogen production
ERMSAR 2012, Cologne, March 21-23, 2012 7
Example of core degradation module assessmentPhébus FP debris experiment
Material distribution at the end of the test
Phébus FPT4 (work performed by IKE-Stuttgart)
Very good agreement (all along the transient up to the end of the test) still using the ICARE advanced 2D magma relocation model
-0.04 -0.02 0.0 0.02 0.04
Radius / m
0.0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
He
igh
t / m
0.050.100.150.200.250.300.350.400.450.500.550.600.650.700.750.800.850.900.95
VolumeFraction
Time=15500s
lower edge ofdebris bed
lowest meltpenetration
0.0
0.1
0.2
0.3
molten pool
void
upper edgeof pool
-0.04 -0.02 0.0 0.02 0.04
Radius / m
0.0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
He
igh
t / m
0.050.100.150.200.250.300.350.400.450.500.550.600.650.700.750.800.850.900.95
VolumeFraction
Time=15500s
lower edge ofdebris bed
lowest meltpenetration
0.0
0.1
0.2
0.3
molten pool
void
upper edgeof pool
250
500
750
1000
1250
1500
1750
2000
2250
2500
2750
3000
3250
0 5000 10000 15000Time (s)
Tem
per
atu
re (
K)
50 mm
153 mm
193 mm
322 mm
heating power
Temperatures at the bed centerline
ERMSAR 2012, Cologne, March 21-23, 2012 8
Example of containment module assessment KAEVER experiments
Pressure evolution Dry aerosols concentrations
KAEVER K123 (test with CsI aerosol in non-saturated atmosphere)
(validation work performed by JSI)
Th. Hydraulics : Very good agreement on pressure & atmosphere temperat.
Aerosols : Very good trend and good order of magnitude for dry aerosols
But results are generally less good for wet aerosols
0 5000 10000 15000 20000 250000
1
2
3
4
K123 experiment ASTEC v2R1
Pre
ssu
re [
bar
]
Time [s]
15000 20000 2500010-6
1x10-4
10-2
100
K123 experiment ASTEC V2R1
Dry
aer
osol
con
c. [g
/m3 ]
Time [s]
ERMSAR 2012, Cologne, March 21-23, 2012 9
Example of containment module assessment MISTRA spray experiments
Atmosphere temperatures in radius R4 Sump water level
MISTRA MASP1 (validation work performed by GRS)
Main Th.Hydraulics effects of spray (pressure, atmosphere drops) are well matched by the CPA module from ASTEC V2.0-rev1
But temperature stratification is overestimated by ASTEC
ERMSAR 2012, Cologne, March 21-23, 2012 10
Example of containment module assessment PANDA SETH free-plume experiments
Test configuration for PANDA test n°18
Steam concentration along the central axis of DW2
PANDA test-18 (validation work jointly performed by IRSN & INRNE)
Reasonable agreement obtained with the CPA module of ASTEC V2.0-rev1 using a refined nodalisation in vertical direction and nodes to model upward plumes recommended nodalization for plant analyses
ERMSAR 2012, Cologne, March 21-23, 2012 11
Example of H2 combustion module assessment BMC experiments
Tested nodalisations Pressure evolution in room R7
where mixture was ignited
BMC Ix9 (validation work performed by RUB)
Sensitivity study on the nodalisation scheme using FRONT model in CPA:
1. Nodalisations A and B : cutting only in horizontal direction (resp. 4 or 8 zones)
2. Nodalisation C : idem A with an additional cutting in vertical direction
Nodalisation influences the convection and therefore the burning rate
Overall, ASTEC V2.0-rev1 results are in good agreement to the experiment
0.8
1.0
1.2
1.4
1.6
1.8
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
pre
ssu
re [b
ar]
time [s]
Nodal_A
Nodal_B
Nodal_C
experiment
ERMSAR 2012, Cologne, March 21-23, 2012 12
Example of MCCI module assessment CCI experiments
Vertical erosion depth Final cavity shape
CCI-5 (validation work performed by UJV)
Quite good results have been achieved with the MEDICIS module of ASTEC V2.0-rev1, using a set of input parameters very consistent with the IRSN recommendations for plant applications
ERMSAR 2012, Cologne, March 21-23, 2012 13
Summary of the ASTEC V2.0 assessment
Th.hydraulics in circuits– Good results on SETs and reasonable results on integral tests (including
CESAR-to-CATHARE detailed benchmarks on SGTR scenarios)
Core degradation
– Good results for both early-phase models (heat-up, H2 production, …) and late phase models (2D relocation, molten pool, corium in lower head, …)
– Poor results in case of a reflooding of a degraded core
FP release– Very good results for volatile and semi-volatile FPs and reasonable results
(slight underestimation) for the low-volatile FPs
FP transport– Reasonable results on FP transport and chemistry
But the importance of the gas chemistry kinetics has been underlined, in particular with respect to the final ST (for instance, iodine partition at the break)
ERMSAR 2012, Cologne, March 21-23, 2012 14
Summary of the ASTEC V2.0 assessment
Containment
– Reasonable results on both thermal-hydraulics and aerosols behaviour
– Poor results on pool-scrubbing phenomena
DCH
– Current models are still too parametric and too geometry-dependent
Iodine and ruthenium chemistry
– Modelling at the State of the Art Global trends are well reproduced No reason to change the strategy yet adopted for several years in that field
which consists in a continuous modelling improvement as a direct feed-back from on-going interpretation of new experiments
MCCI
– Basic relevance of the set of models and assumptions
– Need for model improvements on coolability aspects
ERMSAR 2012, Cologne, March 21-23, 2012 15
Feed-back from the code assessmenton code the development process
First step: at short term, the main benefit for SARNET-WP4 partners using ASTEC comes from the periodical release by IRSN and GRS of improved V2.0 versions (revisions or patches)
Last delivered revision : V2.0-rev2 in December 2011– Improvement of the condensation processes in swollen level volumes– Transfer of the COCOSYS model of dry aerosol re-suspension in containment– Improvements of iodine reactions (in particular Ag/I in the sump)– …
Next planned revision : V2.0-rev3 to be delivered end of 2012– Extension of the RCS gas chemistry kinetics to the Cs-I-O-H-B-Mo system– Improved model for iodine interaction with paints under irradiation– 1st models for corium coolability during MCCI (top cooling and bottom cooling) – …– Moreover, besides new models, improvements are also expected from the
continuous interpretation of the experimental programmes underway or planned in SARNET2, ISTP, OECD or in French frame
ERMSAR 2012, Cologne, March 21-23, 2012 16
Towards future ASTEC V2 versions
Second step (medium term): Development of the next generation of ASTEC V2 versions New models under a new code structure
According to the V2.0-rev1 assessment, main ASTEC modelling efforts shall be spent in priority on the following open modelling issues:
– In-vessel SA phase Reflooding of severely degraded cores
RCS
gas chemistry kinetics– Ex-vessel SA phase MCCI, pool-scrubbing and DCH
Moreover, besides new physical models or improvements of existing ones, significant evolutions of the general code structure (and in particular of the core degradation module and its coupling to other ASTEC modules) have been identified few years ago at IRSN as a mandatory step to remove some current V2.0 limitations for plant analyses
To answer these requirements, the preparation of the future V2.1 version (future ASTEC major version) has already started at IRSN and GRS
ERMSAR 2012, Cologne, March 21-23, 2012 17
ASTEC V2.1 main features
End 2013: ASTEC V2.1 version– Integrating most of the SARNET2 knowledge– New CESAR/ICARE coupling (unique t/h in the whole RCS, no more switch after front
end phase), including also a 2D extension of the in-core thermal-hydraulics– Full capabilities for shutdown states and air ingress situations after vessel failure
(complete Ru behaviour also in RCS and advanced models for fuel oxidation under air atmosphere) and improved capabilities for vessel external cooling
– First version of a mechanistic model for reflooding of degraded cores– Extended RCS gas chemistry kinetics (according to available data)– Transfer of the COCOSYS model of DCH– Generalisation of the MDB use (centralized material database) to any ASTEC module– Integrating specific core models for BWR (canisters, sub-channels, …) and CANDU
First version applicable to the major part of Fukushima-Daiichi NPP accidents First version really applicable to spent fuel pool accidents
– Progress towards a “diagnosis” version Interfacing with atmospheric dispersion tools to enhance capabilities of direct comparison with
on-site measurement
– …
ERMSAR 2012, Cologne, March 21-23, 2012 18
Conclusion and perspectives
ASTEC V2 : a reference tool for Gen.II / Gen.III safety analyses
– ASTEC is and will remain a repository of the knowledge gained from international R§D, while progressively integrating the feed-back from the interpretations of Fukushima-Daiichi NPP accidents
– Axes for future ASTEC modelling improvements beyond V2.1 version are fully consistent with the recently updated SARP ranking
See ERMSAR-2012 paper on severe accidents research priorities
Other long-term objectives– Following-up the ASTEC extension to other reactors
Gen.IV SFR, ITER, …
– Progress towards a severe accident simulator
ERMSAR 2012, Cologne, March 21-23, 2012 19
Appendices
ERMSAR 2012, Cologne, March 21-23, 2012 20
ASTEC nodalisation for MISTRA MASP1and PANDA Test-18 simulations
MISTRA MASP1 PANDA test n°18
0
1
2
4
3
5
6
7
N3
N1
N4
N5
N6
N7
N8
N9
N10
N2
0 R1 R2 R3 R4 R5
R4Z060R2Z060 R0Z060
R4Z110 R2Z110 R0Z110
R4Z158R2Z158 R0Z158
R5Z158
R4Z205R2Z205 R0Z205
R5Z205
R4Z260R2Z260 R0Z260
R5Z260
R4Z363R2Z363 R0Z363
R5Z363
R4Z314R2Z314 R0Z314
R5Z314
R4Z413R2Z413 R0Z413
R5Z413
R4Z463R2Z463 R0Z463
R5Z463
R4Z513R2Z513 R0Z513
R5Z513
R4Z563R2Z563 R0Z563
R5Z563
R4Z613R2Z613 R0Z613
R5Z613
R4Z663R2Z663 R0Z663
R5Z663
R4Z713R2Z713 R0Z713
R5Z713
1,285
3,472
3,592
5,376
5,496
7,280
2,12*1,90
1,73 0,71
0,10
0,85
1,35
1,80
2,30
2,90
3,38
3,88
4,38
4,88
5,38
5,88
6,38
6,88
7,38
zones
R0* zones
R5* zones
R4* zones
R2* zones
ERMSAR 2012, Cologne, March 21-23, 2012 21
Sketch of the BMC facility
ERMSAR 2012, Cologne, March 21-23, 2012 22
According to the interpretations with ASTEC of CCI and VULCANO tests with siliceous concrete (CCI-3, CCI5, VULCANO VB-U5), main recommendations for MCCI full scale analyses are :
The use of Bali correlation for convective heat transfer coefficient seems to be appropriate;
The recommended value for the parameter (Tsol/Tliq interpolation parameter to evaluate the solidification temperature) must range within 0.3 – 0.4;
The proper value for the fraction of radiative power towards concrete above the corium seems to be in the range 0.0 – 0.2;
The slag heat transfer coefficient should be angular dependent. Recommended bottom/lateral values are 100.-200./1000 W/m2K;
The recommended value of layer volume swelling factor is 1.2
Set of best-estimate MCCI parameters for plant analyses