Analyses of the MELCOR capability to simulate integral PWR using passive systems in a DBA scenario

This paper is focused on a thermal–hydraulic transient analysis of a generic 300 MWe integral Pressurized Water Reactor (iPWR) based on a passive safety mitigation strategy and dry containment. The main target of the paper is to analyze the MELCOR code's capability to simulate the operation of the passive systems in Small Modular Reactor (SMR) configuration and the consequent plant behavior. The nodalization and the modeling approach used in the MELCOR code have been described in the present work, and a double-ended rupture of the Direct Vessel Injection (DVI) line has been postulated as initiating event. The results of the analysis demonstrated that the MELCOR code can qualitatively replicate the dominant phenomena that drive the passive mitigation strategy's operation. Additionally, the core reflooding was made possible by the operation of the available safety systems, which was adequate to prevent severe accident conditions during the entire simulated transient. The activity has been developed in the framework of SASPAM-SA Horizon Euratom project as the base for further derivative activities focused on assessing the capability of the MELCOR code to simulate the phenomena taking place in postulated plausible severe accident scenarios in iPWR.