Method to calculate boiling and dryout in debris bed using a heat conduction code

A new model was developed which can calculate boiling and dryout in a debris bed using an equivalent heat conductivity through a similarity between heat conduction and two-phase heat transfer. The model can be assembled into an ordinary heat conduction code. Thus the local temperature, boiling and dryout zones in the debris bed and the temperature of surrounding structures can be estimated two- or three-dimensionally. It is verified that the estimated temperature profiles in the debris bed agreed with those of the in-pile experiments. With the method, the coolability of debris beds that may form on reactor internals or vessel following a core meltdown accident was analyzed