Paper submitted to the Governing Board of SASPAM-SA on 21/02/2023

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.

American Nuclear Society has granted permission to reproduce this pre-publication version of a paper that has been 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.