Emergency pressure-releasing system for nuclear reactors

Purpose: To improve the safety of BWR type reactors by accelerating the reduction in the reactor pressure upon actuation of an automatic pressure-releasing system to facilitate the re-flooding for the reactor core. Constitution: A portion of pressure-release valves in an automatic pressure releasing system are automatically opened with a certain time delay after receiving three signals indicating low reactor-water level, high container-pressure and operation of low-pressure reactor spray system or low-pressure injection-system pump, to thereby decrease the pressure of the nuclear reactor. Then, other valves are opened upon receiving a signal indicating the actuation of the automatic pressure-releasing system and the reduction of the reactor pressure. In this way, since release-valves can be opened at the time when the pressure-releasing rate starts to decrease, a rapid pressure-release can be enabled. (Moriyama, K.)