Abstract: A nuclear fission reactor combined with a propellant actuated depressurization and/or water injection valve is disclosed. The depressurization valve releases pressure from a water cooled, steam producing nuclear reactor when required to insure the safety of the reactor. Depressurization of the reactor pressure vessel enables gravity feeding of supplementary coolant water through the water injection valve to the reactor pressure vessel to prevent damage to the fuel core.

Abstract: A redundant reactivity control system, operating in conjunction with other systems in a nuclear power plant, to mitigate the potential consequences of an anticipated transient without scram event, is described. The invention interfaces to a boiling water nuclear reactor with the reactor's neutron monitoring system, standby liquid control system, control rod drive system, reactor recirculation system, reactor water clean-up feed water control system, and control room and local panels. Two divisionally separated control panels include associated detection and actuation logic and the necessary interface logic to other systems to perform the specific functions in response to an anticipated transient without scram event. Each separate division includes two identical channels. Actuation of any associated reactor system by the invention requires the agreement of the two channels within a division.