ASTEC extension to other reactor types than Generation II PWR

The initial IRSN-GRS requirements for the development of the ASTEC European integral codecovered all present and future PWR, VVER and BWR. After 4 years and a half of SARNET activities, theASTEC V1 code is fully applicable to all severe accident scenarios, at power operation, in Gen.II PWR andVVER. Partners performed substantial code assessment tasks on both VVER-440 and 1000 with good resultson validation (such as PACTEL) and benchmarking with other codes on plant sequences.In the frame of preparation of the new series of ASTEC V2 versions that will account for the needs ofevolution expressed by the SARNET partners, the extension to Gen.III PWR is under way. The 1stversionV2.0, planned for march 09, will be applicable to the EPR, in particular its external core-catcher and to newPWR designs with In-Vessel Melt Retention (IVMR), the latter thanks to CEA work. IVS calculations onVVER-440/V213 showed the ASTEC V1 capabilities to evaluate the IVMR possibilities: these capabilitieswill be improved in the future through a coupled analysis of in-vessel corium and cavity cooling circuit.For BWR applications, the KTH ranking of needs of model adaptations was reviewed by GRS. Theseadaptations mainly concern the Reactor Cooling System (RCS) thermal-hydraulics (internal pumps, drier,separator...) and the core degradation (canisters, control rod guide tubes, penetrations in lower head...). Forcore degradation, the scoping application test on the CORA-18 experiment using the current ASTEC V1models (for adaptation to absorber blades and canisters) showed promising results. The GRS benchmark withthe COCOSYS GRS code showed the applicability of the CPA containment module. For ex-vesselphenomena, the only missing model is the formation of a debris bed during corium slump from lower headinto a flooded cavity after lower head failure and its coolability/erosion behaviour with core concreteinteraction under flooded conditions. All other current V1 models can be used, sometimes with minoradaptations or further need of validation, as for iodine behaviour in containment at temperatures up to 1000Kand the possible decomposition of metal iodides to gaseous iodine at these high temperatures in atmosphere.Detailed specifications will be written soon to prepare the development and validation task planned inSARNET2 with the same partners.For CANDU reactors applications, the priority concerns the core degradation due to the peculiarity ofthe vessel geometry (horizontal core, pressure tubes, calandria...). The exploratory plant applications haveshown that all other current models can be used but tests are still necessary to conclude on models of PHT(Primary Heat Transfer) thermal-hydraulics. INR work takes benefit of the AECL knowledge of MAAP4-CANDU models. A significant benefit is foreseen from the BARC (India) work on core degradation modelsin the frame of IRSN-BARC bilateral collaboration.