Reactor core stabilizing device for BWR type reactor

A reactor core stabilizing device comprises a plurality of internal pumps for supplying coolants disposed in a pressure vessel, control rods to be inserted into the reactor core and control rod drives. In addition, there are disposed a trip judging device for judging the presence of internal pump trip and a device for controlling the control rod drives for the insertion of the control rods and extraction inhibition of the control rods when the trip is judged by the judging device. In such a reactor core stabilizing device, operation of the selective control rod insertion (SRI) and the control rod extraction inhibition can be conducted automatically by using power source ON-OFF signals for individual internal pumps, voltage or current signals, number of rotations of individual pumps, etc. Accordingly, such an operation as hindering the operational stability of the nuclear reactor can be prevented by enable improvement for the operational reliability and operators' burden. (K.M.)