Modeling and numerical simulation of a solidification/fusion front at the interface of a liquid corium pool

This manuscript deals with the numerical simulation of phase change (solidification or fusion of materials) for 'severe accident' in nuclear power plant study. In this context, usually, lack of knowledge of the underlying physics and phenomenology, associated to limited computer resources force the use of coupled heterogeneous models. However, the increase in computer power resources allow nowadays to consider larger and more complex CFD models. In this work, specifically, we consider the simulation of solidification and fusion phenomena between a hot liquid (the so-called corium) which may solidify in contact with a colder solid (for instance, the reactor vessel made of steel). The objective of the PhD is to present new numerical tools to follow fusion/solidification phase fronts. These tools have been integrated in simulation codes dedicated to the modeling of severe accident. A first coupling approach between heterogeneous 0D/2D models, associated with its multi-dimensional numerical method has been developed into the platform PROCOR. Next, a 3D monolithic CFD model has been designed. TrioCFD simulation code has been used as the basis for the development of our numerical methods well suited to handle phase changes between liquid and solid. The proposed developments were tested and validated on simulation configurations representative of the severe accident context. (author)