Abstract： M out of N judgment system is the redundancy design of the reactor protection system.Two quantitative indica- tors-the rate of refuse to operate and misoperation rate-are analyzed.A strict mathematical formula and the approximate calculation are stated. They were used in explaining why M out of N is 2 out of 4 or 2 out of 3 in engineering area usually. The difference of a se- ries of judgment system are discussed in detail when the non-security failure probability and the security failure probability are all 0.1. According to the des...
