Fast Breeder Safety against Propagation of Local Failures

Abstract The propagation of local subassembly failures is considered one of the possible causes for core disruptive accidents (CDA) in liquid metal fast breeder reactors (LMFBRs). Failure to detect local blockages by the delayed neutron detection system or by the thermocouples located at the fuel element outlet may result in subassembly molten fuel-sodium interactions with the potential to put into the core positive reactivity or reduce the shutdown capacity. In the SNR 300 there are three important inherent or engineered barriers to prevent this type of accident: the early detection of local blockages, the proof of low probability of subassembly boiling and dryout, and the proof of the inherent ability to withstand the pressure pulses caused by molten fuel-sodium interactions. It is concluded that it will be possible to demonstrate that the probability of CDAs caused by local failure propagation is very low.