Water level and pressure control device upon isolation of reactors

Purpose: To enable automatic control for the pressure and reactor water level upon isolation of nuclear reactor and significantly decrease the thermal stresses on the reactor materials due to the supply of low temperature water. Constitution: In a case where a main steam isolation valve of BWR type reactor is colsed to isolate the reactor, a flow control valve is controlled by a flow detector that detects the steam flow rate in a main steam relief pipe to thereby release a portion of the main steams to a pressure suppression chamber thereby maintain the reactor pressure to a predetermined value. While on the other hand, feedwater corresponding to the released amount of steams is injected into the reactor core by a pump driven from an auxiliary turbine depending on the detection signal from the flow rate detector and the level detector to thereby attain the intended purpose. (Nakamoto, H.)