Mass transfer experiments on the natural convection heat transfer of the oxide pool in a three-layer configuration

We investigated the heat load to the reactor vessel by the natural convection of the core melt in a hypothetical severe nuclear power plant accident condition. It is modeled as the natural convection heat transfer with the volumetric heat source in a chopped hemisphere. To achieve high Ra'H ranging from 1011 to 1013, mass transfer experiments were performed for three-layer configuration of the oxide pool with three different aspect ratios based on the analogy between heat and mass transfer. The local heat transfers to top, side, and bottom were measured, compared with the existing studies, and discussed phenomenologically. Major findings were that the side and bottom heat flux distributions are unaffected by the top plate cooling condition and that the angle dependent heat flux increases with the angle measured from the bottom. Three layer configuration is more conservative as its upward heat ratio was larger than that of two layer configuration. With the decrease of the aspect ratio, the upward heat ratios increased due to the reduced side wall cooling but with very small aspect ratio, multi-cell flow patterns were formed. The heat transfer around the edge of the bottom plate was impaired due to the formation of stagnant flows.