Multichannel Model for Relocation of Molten Fuel Cladding in Unprotected Loss-of-Flow Accidents in Liquid-Metal Fast Breeder Reactors

During an unprotected undercooling accident in a liquid-metal fast breeder reactor, the motion and relocation of the molten fuel cladding can be important because of their potentially significant effect on reactivity, blockage formation, and subsequent fuel motion. The present study analyzes the cladding relocation problem based on a multichannel film flow model. The important aspects considered in the analysis are the nonuniform transverse cladding melting pattern and sodium vapor flow diversions within a subassembly. It has been shown that the motion of molten fuel cladding and subsequent blockage formations can be significantly influenced by this interconnected channel effect. Several sample calculations have been made to demonstrate these points.