Monitoring device for control rod operation in a reactor

Purpose: To monitor the power distribution near the top end of control rods by calculating the detailed power distribution near the top ends thereof, as well as suppress the effect of the power change due to the control rod withdrawal on the fuels within a range capable of maintaining the fuel soundness. Constitution: Reactor core power distribution calculator determines the power distribution inside the reactor core by receiving signals for various processing amounts. Based on the node output, a power distribution detail calculator calculates the power distribution for the fuel assemblies near the top end of control rods and outputs the results to a power density and power density fluctuation calculator to thereby calculate the power per unit length of the fuel (total power density) and the fluctuation per axial unit length of the fuel assembly for the total power density. The control rod withdrawal forecasting monitoring device receives the signals from the power density and power density fluctuation calculator, forecasts the withdrawable distance depending on the fluctuation in the power density and, after the withdrawal, calculates the increment in the power density to check whether it is within the limiting value of the increment. (Yoshino, Y.)