Severe accidents can cause significant damage to reactor fuel resulting in more or less significant core meltdown and threaten the containment integrity. Such accidents are the focus of considerable research, because the release of radioactive products into the environment would have serious consequences well beyond the borders of the State where the damaged plant is located. It is therefore crucial that the best state of knowledge on severe accident phenomenology, qualified computer tools and appropriate methodology should be used uniformly, in order to evaluate the corresponding risks and update former evaluations, taking into account notably the inevitable evolutions in reactor operations (e.g. new type of fuel, higher burn-up, extension of plant life, new generations of reactors). Additional appropriate engineering devices and/or accident management measures may have then to be developed and implemented in order to reduceMore >>