Reactor safety system and operation state display method

The present invention concerns a safety system of an advanced BWR type reactor having a cooling system upon reactor isolation. The operation function of the reactor is determined based on three reactor parameters of 'reactor water level', 'pressure of a dry well' and 'feedwater', based on inherent characteristics of the reactor. When cooling system upon reactor isolation is operated, if is caused by the elevation of a pressure of a dry well, it is considered to be a rupture of a reactor pressure boundary and judged that the reactor core cooling function is actuated. If the water level of the reactor is low, it is judged that a water supplementing function is actuated if the reactor water level is not less than L1.5, and that a reactor core cooling function is actuated if it is less than L1.5. When the water level of the reactor is low, the actuated function is determined depending on presence or the absence of the feedwater. The judged operation function is displayed in a central control room. In addition, the judgement based on the water level of the reactor and the feedwater may be conducted independently or by taking an AND logic for both of them in order to improve the accuracy of the judgment. (N.H.)