MELCOR Model of iPWR and Application to Emergency Planning Zone Study

Abstract

This study undertakes MELCOR modelling and analysis of a generic integral pressurized water reactor (iPWR) system with the goal of informing a broader study on emergency planning zone (EPZ) sizing. The iPWRs are one of the small modular reactor technologies that have high technical readiness and are potentially being considered for near term deployment. To understand possible iPWR accident scenarios/behaviors important to support emergency preparedness, this study uses the severe accident analysis code MELCOR. Station blackout (SBO) was selected as the base case along with other hypothetical accidental scenarios such as loss of steam generator feedwater, failure of the decay heat removal system, breaks at operating pool, and breaks in the containment vessel. The analyses investigate accident progression in the reactor vessel, containment, and operating pool/reactor building, as well as radionuclide releases for the assessed cases to provide insights on EPZs. The simulated cases in this study provide a spectrum of mechanistic source terms that can fit into the broader probabilistic framework of accident frequency that could inform decisions on EPZ sizing.