Daya bay NPP's leakage test optimization following any opening of the reactor coolant system

Based on Daya Bay NPP's Surveillance Requirements for Periodic Test on Safety-Related System and Equipment, the primary pressure requires increased at an absolute pressure of 15.8 MPa subsequent to any operation requiring opening of the RCP, in order to implement primary circuit leakage test. The test is over range the requirement of Technical Specifications for 15.5 ± 0.1 MPa limits on the pressure of the second barrier, which will add safety risk. Through the research on the leakage rate test of the first circuit of the reactor, the purpose of the design of the leakage rate test of the first circuit of the nuclear power plant and the effect of the safety valve changeover on the test content are analyzed. Considering the actual situation of the system and equipment of Daya Bay NPP's, the optimized scheme of the test was worked out through the analysis of the experimental risk and the parameters of the prerequisite for the optimization test. The results show that the leakage pressure of the first circuit of Daya Bay NPP's is adjusted from 15.8 MPa to 15.5 MPa, which can reduce the safety risk of the test and reduce the time limit of over-normal operation range. (authors)