Model for superheated debris-bed quench for severe-accident containment calculations

Core meltdown accidents are being analyzed to develop an understanding of the risk associated with such postulated accidents and to evaluate the impact of possible mitigating engineering safety equipment. An integral feature of these analyses is the determination of containment building pressurization as a result of loadings imposed by the energy stored in the molten core debris. A major source of containment pressurization would result from the ex-vessel thermal interaction between molten core debris and water available beneath the reactor vessel. It has been suggested that the thermal interaction would occur in two stages: (1) the melt fall period during which the melt mixes with water, breaks up and transfers energy to the coolant, and (2) the debris bed or molten pool quench period during which the core debris rests on the concrete beneath the vessel and is cooled by an overlying pool of water. This paper is directed towards development of models to predict the thermal-hydraulic characteristics of superheated beds of solidified core debris which are cooled by water supplied by an overlying pool of water