IVR-ERVC study of 1700 MW class PWR based on MAAP simulation and coupled analysis

Abstract

As an effective severe accident mitigation strategy, in-vessel retention – external reactor vessel cooling (IVR-ERVC) has been applied to some advanced nuclear reactors. In the assessment of AP600-like reactor, the risk oriented accident analysis methodology (ROAAM) has been adopted based on a lumped parameter model, including sensitivity studies about key parameters and bounding scenarios during accident states. In the ROAAM method, the quantity of steel in the metallic layer and zirconium oxidized, and decay power is not deterministic. These three parameters result from reasonable analysis as presented in DOE/ID-10460 that has provided reasonable bounding distributions for AP600. This study has performed a MAAP4 simulation for 1700 MW class PWR and focused on core melting progress and bounding distributions of main parameters. The effectiveness of the IVR-ERVC for 1700 MW class PWR has been assessed in a coupled analysis based on a modified lumped model using MAAP simulation results. This analysis has considered the coupled relations about heat transfer between in- and ex-vessel. Also, this study has discussed the applicability of natural convection heat transfer correlations in molten pool and compared the results between the lumped parameter model and the modified lumped parameter model. The sensitivity analysis about the three parameters discussed above has been conducted. The methodology demonstrated in this paper can be used for severe accident analysis and advanced reactor design. The results obtained so far indicated that it is feasible to apply IVR-ERVC strategy to a large scale PWR.