Reactor stability control device

Purpose: To prevent the reactor state from approaching to a less stable condition in a forced recycling BWR type reactor. Constitution: An output signal is applied by way of in-core measuring instruments and reactor power instruments disposed to the core of a BWR type reactor to a stability monitoring device of a reactor stability control device. A flowrate signal from a reactor core cooling flow rate instrument in a reactor core is also applied to the monitoring device where the degree of stability is calculated for monitoring the stabilized state of the nuclear reactor. While on the other hand, if the stability degree exceeds a predetermined level, insertion and extraction of a predetermined control rod into and from the reactor core are controlled by way of stability degree setter and a selected control rod insertion controller or the like to thereby control the reactor operation. This enables to prevent the reactor state from approaching to a less stable condition while controlling the operation under the monitoring for the stability degree. (Ikeda, J.)