Disposal and analysis for range switch defect of RPN intermediate range

The paper introduces the reactor trip of certain nuclear power plant caused by RPN intermediate range switch defect, when the reactor is commissioned at 0% FP power level. The in-depth analysis and lots of test are carried out after the incident, through which we find out that some common faults increase the probability of reactor protection malfunction by up to 3%. Corrective action is carried out by using the characteristics of RPN system itself. The solution is comprehensive and reliable after full validation in two domestic nuclear power plants. The conclusion is shared with other domestic and foreign nuclear power plants with the same type of equipment. (authors)