Some outcomes of the SARNET network on severe accidents at mid-term of the FP7 project

Forty-two organisations from 21 countries network their capacities of research in SARNET (Severe Accidents Research Network of excellence) to resolve the most important remaining uncertainties and safety issues on severe accidents (SA) in existing and future water-cooled nuclear power plants (NPP). The SARNET2 project started in April 2009 for 4 years in the 7. Framework Programme (FP7) of the European Commission. It includes a large majority of European actors involved in SA research plus a few important non-European ones. At mid-term of the project, some main outcomes of joint research done by the network members on the highest priority issues are presented. The Joint Programme of Activities concerns performance of new experiments, joint analysis of the results of past or new experiments, elaboration of physical models, in order to achieve a common understanding of the physical phenomena. Concerning in-vessel core coolability, there is a significant progress with 2D/3D simulation codes (ICARE/CATHARE and ATHLET-CD), focussing on the enhanced coolability of debris beds by lateral water inflow, especially via the lower regions. These effects are also investigated by several multi-dimensional experimental programmes such as PRELUDE/PEARL. Concerning molten-corium-concrete-interaction, a better understanding of anisotropic ablation observed in experiments has been reached, notably through new experiments using real materials (such as VULCANO) or simulant materials, and through improved modelling in simulation codes. Concerning containment phenomena, several benchmarks were launched among simulation codes (Lumped-Parameter or Computational Fluid Dynamics) on different physical phenomena such as water spray, hydrogen combustion, steam condensation, plus a theoretical benchmark on a generic NPP containment including the most important components. Concerning source term, progress has been made on understanding the volatile iodine formation from painted surfaces and the oxidation of gaseous iodine species in the containment atmosphere, through new dedicated experiments and models. As a central tool for integration of research, the ASTEC integral computer code, jointly developed by IRSN and GRS to predict NPP behaviour during a postulated SA, capitalizes in terms of models the knowledge produced in the network. The main features of the latest version, ASTEC V2.0rev1, are summarized and a few validation results are presented. For dissemination of knowledge in SA area, an educational 1-week course was organized in January 2011, with the next one foreseen in 2012, for staff in regulatory authorities, utilities or NPPs. Mobility between the European partners of young researchers or master/PhD students is being promoted. An important action is the periodic organization of the European Review Meeting on Severe Accident Research (ERMSAR) that has become one of the major worldwide conferences on SA research. (authors)