Phase segregation model and molten pool thermal-hydraulics during molten core-concrete interaction

A new model for melt thermal-hydraulics during molten core concrete interaction (MCCI) is presented. This model assumes that phase segregations occur in the melt, leading to a crust formation composed of refractory materials (UO2-ZrO2). The interface temperature between this crust and the liquid melt is linked to the solid fraction and is calculated on the basis of a thermal equilibrium assumption. The solid fraction is also controlled by conduction heat transfer through the solid crust. It is shown that the temperatures measured in the ACE experiments are recalculated within a maximum deviation of 10% (when referenced to the solidus temperature) without any adjustment. Other important consequences for this new approach are outlined: for physical properties, physico-chemical interactions, fission products behavior, mixing with sacrificial materials, and crust stabilities. (orig.)