Thermophysical Property Calculation of Core Melt Diluted by Oxide Sacrificial Material

Diluting the core melt with oxide sacrificial material (OSM) during in-vessel retention (IVR) is a newly proposed severe-accident-management strategy of advanced LWR. When severe accident occurs, the OSM is melted by the relocated core melt, resulting in the formation of a ternary liquid mixture of core melt and OSM in the corium. To select OSM and evaluate the heat flux on the vessel outer surface, and to assess the feasibility of the dilution design scheme, the thermophysical properties of the formed multi-component mixture should be obtained first. In this paper, the thermophysical properties of Fe₃O₄, TiO₂ and Al₂O₃ were compared. Density, specific heat, thermal conductivity and viscosity of the molten ternary mixture UO₂-ZrO₂-OSM were also calculated.The results show that to ensure the inverse stratification to occur, implying that the oxide layer locates on top of the metallic layer, the required minimum mass of Fe₃O₄ should be larger than that of TiO₂ and Al₂O₃. The specific heat and thermal conductivity of the ternary mixture increase with OSM mass, while the viscosity decreases as the mass of OSM increases. Moreover at a given temperature, the molten mixture with a lower melting point also has a smaller viscosity.