This paper was originally published in the proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), Copyright 2023 by the American Nuclear Society, Downers Grove, Illinois.

This paper is focused on a thermal-hydraulic transient analysis of a generic integral Pressurized Water Reactor (iPWR) based on a passive safety mitigation strategy, a dry containment and an electric power output of about 300 MWe. The main target of the paper is to analyzes the capability of the MELCOR code to simulate the operation of the passive systems in SMR configuration and the consequent plant behavior. The nodalization and the modelling approach used in the MELCOR code has been described in the present work and a double-ended rupture of the Direct Vessel Injection line has been postulated as initiating event. The analyses of the results showed that MELCOR code is able to qualitatively simulate the dominant phenomena driving the operation of the passive mitigation strategy and the operation of the available safety systems were sufficient to avoid dangerous progressions for the whole simulated transient, allowing the core covering. The activity is developed in the framework of SASPAM-SA Horizon Euratom project, and it is the base for further derivative activities focused on assessing the capability of MELCOR code to simulate the phenomena taking place in postulated plausible severe accident scenarios in iPWR.