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Overview of progress of ASTEC Topic J.P. Van Dorsselaere (IRSN), Coordinator of the ASTEC Topic (with the contribution of all ASTEC Topic members). Contents. ASTEC partners Status and perspectives of ASTEC model development and users’ support

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  1. Overview of progress of ASTEC TopicJ.P. Van Dorsselaere (IRSN), Coordinator of the ASTEC Topic (with the contribution of all ASTEC Topic members)

  2. Contents • ASTEC partners • Status and perspectives of ASTEC model development and users’ support • Status and perspectives of ASTEC validation • Status and perspectives of ASTEC benchmarks on plant applications • Conclusions

  3. ASTEC Topic 28 partners (out of IRSN-GRS) in JPA3, and  50 code users. • AECL (Canada) • ARCS (Austria) • BNRA (Bulgaria) • BUTE (Hungary) • CEA (France) • CIEMAT (Spain) • DIMNP (Italy) • EA (Spain) • EDF (France) • ENEA (Italy) • AREVA-NP/SAS (France) • FZK (Germany) • IKE (Germany) • INR (Romania) • INRNE (Bulgaria) • IVS (Slovak. Rep.) • JRC-IE (EC) • JSI (Slovenia) • KTH (Sweden) • LEI (Lithuania) • NRG (Netherlands) • PSI (Swiss) • RUB (Germany) • TRACTEBEL (Belgium) • TUS (Bulgaria) • UJD (Slovak. Rep.) • UJV (Czech rep.) • VEIKI (Hungary) • VUJE (Slovak. Rep.)

  4. USTIA WP (1/3) USTIA WP: ASTEC Users Support, Training and Adaptation. Total JPA3 volume  5 persons / year. • Code version deliveries: ASTEC V1.2 in July 05, V1.3 in Nov.06, V1.3rev1 in June 07, • V1.3rev1: largely increased numerical robustness, improved documentation (main users’ priority)  reference code for current IRSN PSA2 on PWR1300 MWe, • Next updates V1.3revnwill mainly include feedback from IRSN PSA2 on PWR 1300 and SARNET applications.  Most new models are now developed by IRSN and GRS in the future ASTEC V2 versions.

  5. USTIA WP (2/3) • Support to code users: • 2nd ASTEC Users’ Club held by IRSN at Aix-en-Provence (June 06): fruitful discussions between 45 users and Maintenance Team.  3rd Club planned by IRSN in March 08 in Aix-en-Provence. • ASTEC site on SARNET web portal intensively used: news, forums, surveys, models, input decks, access to code updates,… • MARCUS Web-tool intensive use for users-Maintenance team workflow. • Model developments (out of IRSN-GRS): • By CEA on In-vessel late-phase (corium behaviour) and vessel external cooling  See paper S5-4.  IRSN-GRS take currently into account SARNET users’ needs for the future ASTEC V2 series of versions.

  6. USTIA WP (3/3) • Model adaptation to other NPP: • VVER-440 and -1000: no specific need (already many code applications since several years), except core canisters in 440, • BWR: action plan with KTH-IKE detailed specifications in 2007, • Focusing on in-vessel phenomena (in-vessel jet pumps, core canisters, guide tubes and penetrations in lower plenum), • All other modules are already applicable. • CANDU: ASTEC V1 applicable out of the degradation of horizontal cores  Last point to be investigated by INR and AECL in 2007. See also paper S5-2. • RBMK: • FP and containment models already applicable, • Exploratory benchmarks in RAB on early-phase of core degradation.

  7. PHYMA WP (1/3) PHYMA WP: ASTEC model validation against experiments. Total JPA3 volume  7 persons / year. • Synthesis report of ASTEC V1.2 validation (released in Feb.2007) on 39 experiments. • Good results on: • RCS thermalhydraulics and core degradation early-phase, close to reference codes (CATHARE, SCDAP/RELAP5…) (LOFT-LP-FP2, PACTEL, CORA-13, QUENCH),except too low H2 prod. during core quenching, • Core degradation late-phase (FARO, FPT4, OLHF-1), • FP release and RCS transport (Phébus FPT0-1-2-4, COLIMA, STORM, LOFT-LP-FP2), • Containment thermalhydraulics and aerosol behaviour (LACE LA4, PACOS Px1.2, Phébus.FP)  See paper S5-5, • Iodine in containment (Phébus.FPT2, ThAI).

  8. PHYMA WP (2/3) • What will be improved in ASTEC V2: • Core degradation: • Advanced models for 2D corium relocation (ICARE2 models), • Adequate model for reflooding of a degraded core. • MCCI: acceptable MEDICIS results (ACE L4, OECD-CCI2, BETA) with flexible and state of the art models but current international difficulties (for all codes) to fully understand/simulate MCCI phenomenology and to get generic models. R&D under way in Corium and Containment Topics.  DCH: same conclusions than for MCCI. • For FP release and transport in RCS, despite overall good validation results, improvements are planned due to high complexity of phenomena and to importance of correct source term evaluation, in particular: • FP speciation (work in Phébus.FP, ISTP program, and ST Topic), • Aerosol resuspension in RCS.

  9. PHYMA WP (3/3) • Some new tasks in 2007-08: • Extension to In-Vessel late-phase: MASCA, OLHF, SIMECO, LIVE, • Validation of new advanced 2D corium relocation models on LOFT-LP-FP2, TMI2, CORA… • Extension of IODE validation on Phébus.FP, • Spray in containment: TOSQAN/MISTRA, • FP behaviour and H2 combustion in TMI2accident, • CANDU specific channel heat-up experiments, • BWR specific containment experiments (MARVIKEN…). • Need to better account for experimental uncertainties in the validation process.

  10. RAB WP (1/4) RAB: ASTEC benchmarks on plant applications by comparison with other codes (integral and mechanistic codes). Total JPA3 volume  10 persons/year. • 18 ASTEC calculations of SA sequences up to normal end: • Different NPP types: PWR 900, Konvoi 1300, West.1000, VVER-440, VVER-1000, CANDU, RBMK, • Different SA scenarios: SBLOCA, MBLOCA, LBLOCA, SBO, SG loss of feedwater,  6 calculations were coupling all modules up to iodine behaviour in containment. • Computing time mostly around 1/2 real time, except Konvoi 1300 and VVER-440, but the latter similar to MELCOR.

  11. RAB WP (2/4) • Main conclusions on benchmarks with integral codes MELCOR or MAAP4 on PWR and VVER: • Consistency of general trends of results, • Good agreement on RCS t/h, corium masses in lower head, lower head failure time, H2 total production ( 15%),containment t/h, • But the detailed analysis showed some differences due to different models. • Core degradation kinetics, • MCCI because of DIVA stop after vessel failure (improved in V1.3rev1), • FP/aerosol transport in RCS. • Not enough analysis of FP results in JPA3  to be done in details in JPA4. • Need of detailed nodalisation of VVER horizontal SG  Guidelines report.

  12. RAB WP (3/4) • Main conclusions on benchmarks with mechanistic codes: • Good results on RCS t/h and core degradation with ATHLET-CD, acceptable ones with SCDAP/RELAP5, planned in 2008 with ICARE-CATHARE. • Exploratory calculations of In-Vessel Melt Retention: acceptable agreement with existing calculations  see paper S5-4. • Applications to CANDU: • Physically reliable results of a coupled SOPHAEROS-CPA-IODE calculation on FP transport and behaviour: PHT plays a good filter role for FPs. • Applications to RBMK: • Current benchmarks with RELAP5/SCDAPSIM on early-phase of core degradation.

  13. RAB WP (4/4) • Perspectives in 2007-08: • Verification of V1.3 revn improvements and extension to the detailed analysis of FP results, • Some benchmarks on limited parts of SA scenarios with well-imposed conditions: example of MCCI, • CANDU benchmarks with CATHENA for PHT thermalhydraulics and possibly with MAAP4/CANDU (both used by AECL), • BWR benchmarks on containment, • Trend to multiply ASTEC sensitivity studies on the most influent model parameters.

  14. General conclusions (1/2) • Status of JPA3: • Validation: good overall results, sometimes reaching limits of present knowledge (MCCI, DCH). • Code large robustness increase allowed full benchmarks on plant applications. Need now to focus more on FP results. • Action plans defined for BWR and CANDU model adaptation and benchmarks. • Reinforced importance of comparisons with detailed codes and with experiments. • New V2 series under preparation (ASTEC V2.0 in late 2008): • ICARE2 module for core degradation, • Reflooding of a degraded core, • Applicability to EPR, • Ru behaviour in circuit and containment, for air ingress situations.

  15. General conclusions (2/2) • ASTEC progressively becomes the reference European integral code for SA safety studies in present PWR-VVER: • Models at the current State of the Art, with clearly a lead position on fission product behaviour, • High level of validation, • New or improved models (mainly from ST Topic) to be implemented in 2007-08. • Future code evolutions: • Repository of knowledge created in R&D on remaining key-safety issues, • Trend to progressively incorporate more mechanistic models, • Deeper use for emergency response applications or simulators, • Applications to other reactor types: ITER, VHTR…

  16. CESAR-DIVA validation • LOFT-LP-FP2 (work by ENEA, Italy): • CESAR-DIVA overall response rather satisfactory before bundle reflooding: transient t/h, H2 release, FP release fractions, • But model improvements necessary for the reflooding phase. Primary and secondary pressure Clad temp. around core axial mid-level

  17. SOPHAEROS validation • STORM SR11(ISP40) (work by JRC): simulation with SOPHAEROS of aerosols mechanical resuspension. • 2 models: better agreement on kinetics with JRC Rock n’Roll model but better agreement on final resuspended mass with Force Balance model.

  18. MEDICIS validation • OECD-CCI2 (work by UJV): simulation with MEDICIS of MCCI. • Consistent results of validation on ACE, BETA and OECD-CCI2 exp. using a fixed set of model parameters, in particular the corium solidification temperature near Tliquidus and standard heat transfer correlations. Mass of eroded concrete Final cavity shape

  19. LFW-SG sequence in PWR 900 PWR900: LFW-SG sequence (AREVA NP work) with ASTEC V1.2 and MAAP4, • Agreement on RCS t/h (see below) and on containment t/h (see lower right), • Different H2 masses but no activation in DIVA of steel oxidation and absence of corium fragmentation model (now in ASTEC V1.3).

  20. LBLOCA benchmark in Konvoi-1300 Konvoi 1300: MBLOCA (work by IKE) between ASTEC V1.2 and ATHLET-CD on RCS t/h and early-phase core degradation, • Close thermal-hydraulic behaviour, • Earlier start of H2 production and core melting in ASTEC calculations due to faster core de-watering. Same range of produced H2 masses.

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