Control-rod-withdrawal monitor in BWR type reactor

Purpose: To secure the safety of a fuel by early blocking for control rod withdrawal. Constitution: The local power is monitored around a control rod so as to block the control rod withdrawal in the case as the power exceeds the predetermined set value, for which a correcting circuit of (R - R0)xC R0 is provided, where R0 represents the initial value of the average power value and hence the average power value at the time of selecting the control rod, R represents the average power value during the discharging of the control rod, and C represents a positive constant. The discharging operation of the local power is achieved with correcting signal from the circuit. Since the maximum value of the increased local power can be reduced as compared with the conventional one in this manner, the safety of the fuel can be always secured. (Kamimura, M.)