Reactor core water recirculation flow rate control system

A recirculation pump for removing heat generated in a boiling water type reactor is driven by a pole change type motor connected to a variable frequency type power generator equipped with a steam turbine which is driven by a portion of the steam from a main steam system through a control valve for controlling the turbine speed, i.e., the output frequency of the power generator. The pole change motor is further connected to a commercially available power line through a circuit breaker. In starting operation, the circuit breaker is closed to start the motor by employing the power line, while the exciter of the power generator is left deenergized. As the reactor power is raised, the steam produced is applied to the turbine so as to equalize the output frequency of the power generator and that of the power line. The switch is then opened and the exciter of the power generator is energized to drive the motor by the output of the power generator. Since the rotation speeds of the power generator and motor are equal to each other, no large current flows in transient in this switching of the power. Once the power is switched, the control valve is controlled to adjust the power of the reactor. (Ohno, Y.)