JPS6415693A - Operation of nuclear reactor - Google Patents

Abstract

PURPOSE:To prevent the mechanical vibration of an in-pile machinery and to stably lower the output of a reactor core, by stepwise controlling the number of rotations of the recirculation pumps in all of nuclear reactors at the time of a transparent phenomenon. CONSTITUTION:When a transient phenomenon such as the lowering in the water level of a nuclear reactor or the rising in the pressure thereof is generated during the operation of the nuclear reactor, multistage control of two or more stages, such that the number of times of the recirculation pumps in all of the nuclear reactors are once uniformly lowered to 50% or less at first and again raised immediately after, is performed. Considering a pump characteristic and the shape of the flow passage reaching a lower plenum 12 from a downcomer 11, the control rate of the number of the rotations of the pump is determined. By this constitution, since the flow rate at the inlet of a reactor core shows a coast down characteristic, partial flow rate unbalance is not generated and the flow rate/output vibration of a reactor core part and the mechanical vibration of in-pile constitutional machinery can be prevented and the stable lowering in a flow rate can be performed and, therefore, the output of the reactor core can be lowered without hindrance.