Reactor power forecasting device in nuclear power plant

Purpose: To enable reactor power control in a BWR type reactor based on forecast values conformed with actual circumstances. Constitution: A reactor core performance calculator calculates the core performance based on the reactor core data obtained from process amount detectors such as for the position of control rods inserted into the reactor, neutron fluxes in the reactor core, core flow rate, pressure, temperature and the like. Then, a xenon density distribution calculator calculates the present value for the changes in the axial xenon distribution density and an axial reactor power distribution forecasting device determines the reactor power forecast values based on a one-dimensional diffusion model in the core axial direction rapidly and accurately. In the calculation for the forecast values, the number of control rods in adjacent with the control rods to be treated is determined depending on the control rod density and compensating calculation is performed based on a curve of control rod reactivity versus number of adjacent control rods. Accordingly, the forecast values conformed with the actual circumstances are obtained and the reactor power of the nuclear power plant can properly by controlled with no excess control. (Seki, T.)