Status of steam explosion understanding and modelling

•State of the art regarding fuel–coolant interaction and steam explosion.•Review major outcomes of the OECD program SERENA-2 and activities in SARNET-2.•Review of major recent improvements related to understanding and modelling.•Highlight the major needs for reducing uncertainties for reactor applications.•Provide a priority ranking for the further needs. The main results of the major international activities related to fuel–coolant interactions (FCI) of the last 4-year period are presented and a summary of the knowledge gained regarding understanding and the improvements of modelling is provided. At first, the major outcomes of the OECD SERENA-2 program are presented and discussed. Important clarifications were obtained on the so-called material effect and on FCI code capabilities. We then summarise complementary analytical analyses and experimental programs performed in the frame of the SARNET community. The focus was put on the role of melt fragmentation and solidification, the impact of void on the intensity of an explosion and the triggering mechanisms. As a conclusion, tables summarising the improvements are proposed as well as research priorities.