Overview of progress of ASTEC Topic J'P' Van Dorsselaere IRSN, Coordinator of the ASTEC Topic with t

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

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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.)

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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 V1.3revn will 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.

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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.

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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.

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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).

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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. RD
  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.

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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 TMI2 accident,
• CANDU specific channel heat-up experiments,
• BWR specific containment experiments (MARVIKEN).
• Need to better account for experimental
  uncertainties in the validation process.

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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.

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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.

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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.

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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.

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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.

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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 RD 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

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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
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SOPHAEROS validation

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

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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
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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).

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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.