Thermomechanical simulations of concrete behaviour during molten core-concrete interaction

Within the framework of nuclear safety, hypothetical severe accidents are studied, dealing with the melting of the core of a reactor. The resulting molten mixture could flow through the pressure vessel and fall on a concrete basemat. In such a situation, a complex interaction would start, involving several chemical-thermal-physical processes, leading to the fusion (also called ablation) and cracking of concrete. A complete methodology, using finite element analysis, has been developed to represent the thermomechanical behaviour of a melting concrete structure in such a context. The originality of this work is that the model takes into account the ablation process of the concrete structure and identifies crack formation. The model is validated on an experiment which consisted of pouring prototypic molten corium to a concrete crucible. During this test, the crucible cracked and the corium spilled out. The purpose of this work is to initiate a predictive simulation tool contributing to the understanding of the dominant phenomena in the accidental scenario.