Two dimensional fuel motion analysis during loss-of-flow accidents in a liquid metal cooled fast breeder reactor. Annual progress report, July 1, 1975--July 1, 1976

An ongoing research program to analyze two dimensional fuel motion in the pre-disassembly stage of a loss-of-flow accident in a liquid metal fast breeder reactor is outlined. The analysis is based on a model channel, consisting of an isolated single fuel pin with cladding and associated subassembly containment structure. A mathematical model is set up to describe the motion of the seven materials of interest: liquid fuel, liquid steel, solid fuel, solid steel, vapor fuel, vapor steel and gaseous fission products. These materials are treated as distinct fields, each with its own equation of density, momentum and energy transport. The various fields are linked together via binary exchange functions for mass, momentum and energy transfer. The exchange functions can be manipulated to give any desired degree of linkage between two fields. The flow analysis is carried through up to the point of loss of subassembly integrity, when a switch to a disassembly code must be made