Dryout predictions for liquid boiling in a thin hemispherical porous layer

During TMI-2 accident a gap was formed between reactor vessel bottom and core debris bed. This gap is thought to provide high cooling rates. In the present paper additional heat removal mechanism due to gap is modeled as boiling of coolant in a thin hemispherical heated porous layer. Corresponding dryout power is found as a function of debris bed permeability and material properties of liquid and its vapor. Conditions are assessed at which heat removal by boiling in the gap is noticeable and should be taken into account in analysis of debris cooling inside reactor vessel.