BFS critical assembly studies of the fast reactor safety

The authors describe computer simulation studies of fuel element failure analyses in critical assemblies and sodium void reactivity effects both for uranium (BFS-21, 22, 24, 39, and 45) and mixed uranium and plutonium (BFS-34, 44, and 46) critical assemblies in sodium-cooled fast breeder reactors. Some assemblies were used for measuring reactivity effects due to the entrance of hydrogenous substances into the core. Extensive investigations were conducted for measuring reactivity effects in a failure situation with destruction of the fuel assemblies. Calculated values for these effects were obtained in the diffusion approximation by first-order perturbation theory. Some of the reactors considered include the BOR-60 and the BN-350