Overview of the ASTEC V2.0-rev1 validation

Transcription

1 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 Contents 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 ERMSAR 2012, Cologne, March 21-23,

3 ASTEC context and objectives IRSN-GRS cooperation since 1996 for development of an integral code ASTEC (Accident Source Term Evaluation Code) for present/future nuclear watercooled 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 1 st period) Mid-2010 : V2.0-rev1 Extended V2 validation by number of partners (SARNET2 2 nd period) End-2011 : V2.0-rev2 Validation to be continued in the frame of SARNET2 3 rd period ERMSAR 2012, Cologne, March 21-23,

4 ASTEC V2 A new series of versions (1/2) ERMSAR 2012, Cologne, March 21-23,

5 ASTEC V2.0-rev1 validation 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), (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,

6 Example of core degradation module assessment Phébus 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,

7 Temperature (K) Example of core degradation module assessment Phébus FP debris experiment 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 heating power mm 193 mm 50 mm 153 mm Time (s) Temperatures at the bed centerline void upper edge of pool molten pool lowest melt penetration lower edge of debris bed Height / m 0.3 Time=15500s Radius / m Volume Fraction Material distribution at the end of the test ERMSAR 2012, Cologne, March 21-23,

8 Pressure [bar] Dry aerosol conc. [g/m 3 ] Example of containment module assessment KAEVER experiments 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 4 3 K123 experiment ASTEC v2r x10-4 K123 experiment ASTEC V2R Time [s] Pressure evolution Time [s] Dry aerosols concentrations ERMSAR 2012, Cologne, March 21-23,

9 Example of containment module assessment MISTRA spray experiments 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 Atmosphere temperatures in radius R4 Sump water level ERMSAR 2012, Cologne, March 21-23,

10 Example of containment module assessment PANDA SETH free-plume experiments 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 Test configuration for PANDA test n 18 Steam concentration along the central axis of DW2 ERMSAR 2012, Cologne, March 21-23,

11 pressure [bar] Example of H 2 combustion module assessment BMC experiments 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 Nodal_A Nodal_B Nodal_C experiment Tested nodalisations time [s] Pressure evolution in room R7 where mixture was ignited ERMSAR 2012, Cologne, March 21-23,

12 Example of MCCI module assessment CCI experiments 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 Vertical erosion depth Final cavity shape ERMSAR 2012, Cologne, March 21-23,

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, H 2 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,

14 Summary of the ASTEC V2.0 assessment Containment DCH Reasonable results on both thermal-hydraulics and aerosols behaviour Poor results on pool-scrubbing phenomena Current models are still too parametric and too geometry-dependent Iodine and ruthenium chemistry MCCI 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 Basic relevance of the set of models and assumptions Need for model improvements on coolability aspects ERMSAR 2012, Cologne, March 21-23,

15 Feed-back from the code assessment on 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 1 st 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,

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,

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,

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,

19 Appendices ERMSAR 2012, Cologne, March 21-23,

20 ASTEC nodalisation for MISTRA MASP1 and PANDA Test-18 simulations zones 0 R1 R2 R3 R4 R5 7,38 7 R5Z713 R2Z713 R4Z713 6,88 R0Z713 7,280 N10 R5Z663 R4Z663 R2Z663 6,38 R0Z663 N9 6 R5Z613 R4Z613 R2Z613 5,88 R0Z613 R5Z563 R2Z563 5,38 R4Z563 R0Z563 5,496 N8 5 R5Z513 R4Z513 R2Z513 4,88 R0Z513 5,376 R5* zones R5Z463 R2Z463 4,38 R4Z463 R0Z463 N7 R0* zones R2* zones R4* zones R5Z413 R2Z413 R0Z413 3,88 R4Z413 R5Z363 R2Z363 R0Z363 3,38 R4Z363 R5Z314 R2Z314 R0Z314 2,90 R4Z314 R5Z260 R2Z260 R0Z260 2,30 R4Z260 R5Z205 R4Z205 R2Z205 R0Z205 1,80 R5Z158 R2Z158 R0Z158 1,35 R4Z158 R4Z110 R2Z110 R0Z110 0,85 3,592 3,472 1,285 N6 N5 N4 N3 N2 R4Z060 R2Z060 R0Z060 N1 0 0,10 2,12* 1,73 0,71 1,90 MISTRA MASP1 PANDA test n 18 ERMSAR 2012, Cologne, March 21-23,

21 Sketch of the BMC facility ERMSAR 2012, Cologne, March 21-23,

22 Set of best-estimate MCCI parameters for plant analyses 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 ; The proper value for the fraction of radiative power towards concrete above the corium seems to be in the range ; The slag heat transfer coefficient should be angular dependent. Recommended bottom/lateral values are /1000 W/m2K; The recommended value of layer volume swelling factor is 1.2 ERMSAR 2012, Cologne, March 21-23,