To avoid unnecessary reactor water level lowering, plant emergency stop, or operation in an operation restriction domain at a shortage time of a water supply pump capacity, with simple equipment.

This device includes a runback interlock 15 for running back a recirculation pump up to recirculation pump runback speed when the water supply pump capacity for supplying water to the reactor in a boiling-water nuclear power plant becomes short; a control rod selection circuit 16 for selecting a control rod to be inserted, based on a present insertion position of the control rod insertable into the core of the reactor; and a control rod insertion signal output circuit 17 for outputting a control rod insertion signal to the control rod selected by the control rod selection circuit 16.