Forty-three organisations from 22 countries network their capacities of research in SARNET (Severe Accident Research NETwork of excellence) to resolve the most important remaining uncertainties and safety issues on severe accidents in existing and future water-cooled nuclear power plants (NPP). After a first project in the 6th Framework Programme (FP6) of the European Commission, the SARNET2 project, coordinated by IRSN, started in April 2009 for 4 years in the FP7 frame. After 2,5 years, some main outcomes of joint research (modelling and experiments) by the network members on the highest priority issues are presented: in-vessel degraded core coolability, molten-corium-concrete-interaction, containment phenomena (water spray, hydrogen combustion…), source term issues (mainly iodine behaviour). The ASTEC integral computer code, jointly developed by IRSN and GRS to predict the NPP SA behaviour, capitalizes in terms of models the knowledge produced in the network: a few validation results are presented. For dissemination of knowledge, an educational 1-week course was organized for young researchers or students in January 2011, and a two-day course is planned mid-2012 for senior staff. Mobility of young researchers or students between the European partners is being promoted. The ERMSAR conference is becoming the major worldwide conference on SA research. 1. Introduction Despite the accident prevention measures adopted in nuclear power plants (NPPs), some accident scenarios, in very low probability circumstances, may result in severe accidents (SA) with core melting and plant damage and to dispersal of radioactive materials into the environment, thus constituting a hazard for the public health and for the environment. This was unfortunately underlined by the accidents in the Japanese Fukushima-Daiichi NPPs in March 2011. After 4 years in the 6th Framework Programme (FP6) of the European Commission, the SARNET (Severe Accident Research NETwork of Excellence) network (http://www.sar-net.eu), coordinated by the French Institut de Radioprotection et de S？reté Nucléaire (IRSN), is continuing to operate in FP7 [1] for 4 years since April 2009. The objective is to enhance the coordination of the national efforts in order to optimise the use of the available expertise and the experimental facilities for resolving the remaining issues for enhancing the safety of existing and future NPPs. The work focuses on the highest priority safety issues still to be resolved [2], including the realization of experiments and the assessment of the ASTEC integral computer code [3],
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