Severe Accident Simulations Dedicated to the SAMG Decision-Making Tool Demonstration

The paper presents preliminary severe accident (SA) simulations performed to generate a database of plant states dedicated to be used with Severe Accident Management Guidelines Decision Making Tool (SAMG DM). The novel software is being developed in the framework of the NARSIS Horizon-2020 research project. It is intended to be a supporting tool for the SAMGs implementation, Emergency Preparedness and selection of Severe Accident Management (SAM) strategies. Simulations were performed with MELCOR 2.2 integral computer code for generic Nuclear Power Plant (NPP) with Gen-II Pressurized Water Reactor (PWR). The database covers results for parameters important for both in-vessel and ex-vessel phases of different accident scenarios. Two general types of scenarios are considered in the database: low-pressure and high-pressure sequences. In this paper, a comparison was prepared for two base case low-pressure scenarios, that is hot leg and cold leg LB-LOCAs without safety injection. Sensitivity simulations were performed with and without Containment Filtered Venting (CFV) as it substantially influences the containment performance. Both accidents are characterized by rapid progression with core meltdown within 2 hours and containment failure within 40 hours and eventual venting with CFV after 13-15 hours. It was observed that for the cold-leg break, the Reactor Pressure Vessel failure occurs earlier only by similar to 5 minutes. On the contrary, the containment failure is predicted to occur three hours earlier for the hot-leg LOCA.