Research on the possibility of material mixing and interaction in the lower head based on specific corium relocation process

MASCA experiment indicated the possibility of oxidic and metallic material interaction and the following analysis produced a possible 3-layer configuration in the lower head. However, 3-layer corium pool is valid only under the circumstance that materials are well mixed. This assumption has not been studied thoroughly in IVR analysis. In this paper, a CFD code is used to predict the possibility of material mixing based on the MAAP4 results and conservative assumptions. The analysis indicates that the validated LES model and a grid of y+ < 10 can well predict thermal hydraulics in the oxide and metal phase, thus producing boundary conditions for the crust integrity analysis. The stress in the crust is calculated by ANSYS code to determine the integrity of crust by comparison with MACE experiments. The results show that the crust is likely to maintain its integrity and keep the oxidic and metallic materials separated, thus restricting the material interaction. This study may support a 2-layer corium pool configuration in the lower head.