Patent Number: 
Section: claims

1. A control method of a control system of a nuclear power plant including M detection units that detect a phenomenon occurring in a nuclear power plant for each of M systems and a start unit that starts processing corresponding to the phenomenon in a case where a signal that indicates an occurrence of the phenomenon is input from a predetermined number or more of signal lines out of L signal lines, for controlling a transmission of a signal between the M detection units and the start unit, the method comprising:providing a plurality of majority circuits as many as the L signal lines such that each of the plurality of majority circuits is connected to each of the signal lines one by one and all outputs from the M detection units are inputted to each of the plurality of majority circuits;receiving, by the majority circuit provided for each of the L signal lines, a signal that indicates whether the phenomenon is detected from all of the M systems, andoutputting, by the majority circuit, a signal that indicates an occurrence of the phenomenon to a corresponding signal line in a case where a signal indicating that the phenomenon is detected is received from N or more systems out of the M systems,wherein L is an integer greater than or equal to 1, M is an integer greater than or equal to 2 being larger than L, and N is an integer greater than or equal to 1.