BWR-incorporated coolant recycling device and operation method therefor

An induction electromotive/electric generator is operated as an electric generator by remaining current based on signals of instantaneous power stoppage or loss of power of AC bus in a station to convert an inertia energy stored in flywheels to AC power. It is converted to DC power by way of a controlled inverter device, so that a variable voltage variable frequency power source device (VVVF) can output a DC voltage which can supply an AC voltage having a frequency corresponding to the operation speed of an incorporated type underwater induction electromotive recycling pump (RIP). The voltage is supplied to a series circuit on the side of a rectifier output of the VVVF, so that the operation of the RIP can be continued for a predetermined period of time. Then, the reactor-incorporated coolant recycling device can be operated at a predetermined rated flow rate or predetermined flow rate coast down operation can be conducted thereby enabling to suppress thermal damages of fuel rods, reduce the number of RIP systems and reduce the initial investment of facilities for power generation and cost for inspection and maintenance. (N.H.)