Reactor power control device

The present invention concerns a device for stably controlling the power distribution in the reactor core, upon selected control rod insertion, to suppress water level fluctuations of the reactor in a BWR type power plant. That is, a recycling pump trip detection device detects recycling pump tripping. A selected control rod insertion device inserts selected control rods to the reactor core at a low speed by the trip signals. With such procedures, lowering of the reactor water level accompanied by the abrupt reduction of voids in the reactor core is suppressed. Further, the trip signals are also inputted to a comparator. The comparator compares the signals of each of local power range monitors (LPRM) from various heights with each of reference values inputted from a reference standard value setting device. This can monitor the distortion of the power distribution at the periphery of the inserted control rods. When the distortion deteriorates the thermal integrity of fuels, the selected control rod insertion device rapidly inserts selected control rods to the reactor core, or a scram insertion device rapidly and entirely inserts control rods. As a result, the distortion of the power distribution can be suppressed. (I.S.)