Protection against local core accidents in liquid metal fast breeder reactors

Abstract An analysis is presented concerning the performance characteristics of sensors considered for use in protection systems of liquid metal fast breeder reactors. Alternate solutions to protection systems having one or more reactor-trip channels per fuel subassembly are proposed. Primary emphasis is placed on pressure pulse sensors, installed in the upper (and possibly also lower) coolant plenum, capable of sensing the collapse of sodium vapor bubbles. It is shown that, even for the limit-case of a complete coolant blockage of one or more fuel subassemblies, a reactor protection system based on pressure pulse sensors should be capable of effecting reactor-shutdown prior to generation of any substantial amount of molten fuel. Some preliminary experimental data regarding vapor bubble collapse are presented, showing reasonable agreement with analytical predictions. Recommendations are made regarding some potentially promising areas for further research and development with respect to protection systems for liquid metal fast breeder reactors.