Code to code comparison of a dba sequence in a generic iPWR between MELCOR and ASTEC codes

Nowadays, several integral Pressurised Water Reactor (iPWR) designs are close to the licencing stage since they are based on the well-established technology of large Light Water Reactors (LWRs), incorporating evolutionary design features aimed at enhancing the inherent safety of the plant through integral configurations and adoption of passive safety systems. However, a sound demonstration of iPWRs’ capability to address Severe Accident (SA) should be carried out for a comprehensive safety review process. In this context, the international scientific community is increasingly focusing on assessing SA integral codes in simulating typical iPWRs’ phenomenology during postulated accidental scenarios. The Horizon Euratom project “Safety Analysis of SMR with Passive Mitigation strategies – Severe Accident” (SASPAM – SA), coordinated by ENEA, investigates the applicability, the transfer of the large LWR knowledge and know-how to iPWRs, in view of SA and Emergency Planning Zone (EPZ) licensing analyses needs. In this regard, the present work carried out within the SASPAM-SA project presents a comparative analysis between the SA codes MELCOR and ASTEC. The goal of the study is to evaluate the capability of the codes in simulating the dominant thermal–hydraulic phenomena during a postulated Design Basis Accident (DBA) scenario in a generic 300 MWe iPWR, considering the full availability of the reactor passive safety systems. The code-to-code benchmark highlights the main consistencies and possible discrepancies between the codes.