Case Study on RPN Neutron Flux Change Rate High R.T. in PWR NPP

In the control system of a pressurized water reactor (PWR) nuclear power plant (NPP), the neutron flux change rate of the neutron instrumentsystem (NIS or RPN) is an essential basis for determining whether the reactor should be shut down in an emergency. The calculation of the neutron flux change rate involves the average temperature of primary circuit, the main coolant pump rotation speed, neutron flux rate of the RPN power range channel, the correction block signal such as power level below 10%FP (not P10). This paper takes the mistake partial trip of the RPN Neutron Flux Change Rate High reactor trip (R.T.) in PWR NPP as a case study, starts from the problem phenomenon, lists the possible causes according to the signal flow of the control system, and determines the root cause through step-by-step investigation, and analyzes in detail the precautions for the design of the R.T. logic as well as the improvement measures. The above experience can reference the RPN R.T. design of similar pressurized water reactor nuclear power plants.