Recirculation flow rate control device

Purpose: To prevent the anomalous growth of disturbance by early and accurately finding an abnormal increase in a recirculation flow rate resulting from an error input to the recirculation flow rate control system of a BWR-type reactor, malfunction of the control system, or a trouble with component equipment of the recirculation system, and then by performing a protection operation. Constitution: Signals from a neutron flux meter disposed at the reactor core section and a generator speed meter are used as input signals. A rate of increase in the neutron flux corresponding to the power level is determined from a neutron flux meter signal, and the rate of increase thus determined is compared with a set value set on the basis of the limit value of the rate of increase in the neutron flux required for the retention of integrity of fuel. Furthermore, the rate of increase in the number of revolutions is determined from a generator speed signal and this is also compared continuously with a set value. In consequence, when the rate of increase in the neutron flux is abnormally high and the generator speed is increasing, there will be generated a recirculation pump runback signal, by which the pump speed will be decreased. When the aforementioned number of revolutions continues to increase even after the occurrence of the runback, there will be produced a recirculation pump trip signal. (Horiuchi, T.)