Fuel Motion in Experiments Simulating Liquid-Metal Fast Breeder Reactor Loss-of-Flow Accidents

The reactivity feedback from fuel relocation is a central issue in the analysis of a loss-of-flow (LOF) accident in a liquid-metal fast breeder reactor (LMFBR). Fuel relocation has been the subject of a number of LOF simulations in the Transient Reactor Test Facility (TREAT). In this study, the results of these tests are analyzed using, as the principal figure of merit, the changes in equivalent fuel worth associated with the fuel motion. The equivalent fuel worth was obtained from the measured axial fuel distributions by weighting the data with a typical LMFBR fuel worth function. At nominal power, the initial fuel relocation resulted in increases in equivalent fuel worth. Above nominal power, the fuel motion was mildly dispersive, but the dispersive driving forces could not unequivocally be identified.