Plant application of ICARE/ASTECv2.0r3 computer code for investigation of in-vessel melt retention in VVER-1000 reactor design

Abstract

This investigation was done to assess the applicability of the In-Vessel Melt Retention (IVMR) strategy with external vessel water cooling for the reactors of VVER-1000/320 type. The IVMR strategy has been studied in different countries and the existing knowledge can assess the applicability of the strategy for VVER-1000/320 reactors and to identify the main remaining issues.IVMR strategy is one of the feasible solutions to mitigate severe accidents of VVER-1000/320 reactors but it needs to be further developed and optimized.The analytical work aimed at further identification and verification of conditions for successful IVMR application. The results achieved with severe accident computer codes like ASTEC could predict these conditions. The priority issues evaluated in this paper are the heat transfer from the corium to the reactor pressure vessel (RPV) and the heat transfer from the RPV to water outside the vessel.ICARE/ASTECv2.0r3 computer code was used to predict the heat fluxes from the corium to the vessel and the heat fluxes from the vessel to the outside coolant. It highlighted key periods of maximum heat input to the vessel steel wall that the steel wall has to be capable of sustaining.