Reliability Evaluation And Software Development Of 650MW Nuclear Power Unit's Engineered Safety Feature

Engineered safety Feature plays a very important role in the occurrence of design basis accidents in nuclear power plants and is an important part of defense-in-depth principles of the nuclear reactor.In the event of a water loss accident,Engineered safety Feature can urgently shut down the reactor,provide a cold source for the reactor,and discharge the residual heat of the core,thereby alleviating the severity of the accident.These systems are used at a low frequency and are always in a standby state under normal conditions.If a concealed function failure occurs,a nuclear accident may occur,and the consequences are very serious.At present,domestic and foreign scholars have very little quantitative analysis on the reliability of the dedicated safety facilities,and the reliability of these systems has not been studied in depth.Therefore,the quantitative reliability calculation of each system in the Engineered safety Feature,the weak link analysis and the life prediction of each system can provide reference for the equipment maintenance of the Engineered safety Feature of the nuclear power unit and similar safety problems of other systems.It is of great significance to the safe and economic operation of nuclear power units.This paper analyzes and studies the safety injection system in the Engineered safety Feature of a 650 MW nuclear power unit in China.The specific contents and results are as follows:(1)It is assumed that the life of each equipment of the system is subject to the three-parameter Weibull distribution,classified according to the function,model and manufacturer of the equipment,combined with the actual fault data of the site,using the grey estimation method(GME)and the maximum likelihood estimation method combined with the simulated annealing algorithm.(MLE-SA),grey-maximum likelihood estimation(GM-MLE)and double bilinear regression estimation(DLSE)are used to estimate the Weibull distribution of each device,and then the results are fitted by K-S method.Degree test,complete correctness verification,prove that the life expectancy of each equipment obeys the Weibull distribution,and compare the correlation coefficient of each equipment under each estimation method,and calculate the corresponding failure rate,and the average failure rate of the equipment in the actual engineering report.Compare and find a set of optimal fitting parameters for each device to get the final life distribution function.(2)Study the working principle,equipment composition and operation flow of the safety injection system,combine the reliability function of each equipment,and use the reliability block diagram method to calculate the reliability function expression of each subsystem under each stage of the safety injection system work,and The system carried out life prediction analysis,calculated the reliability of each subsystem when it was running for 18 months,and compared with the actual operation of the field to verify the correctness of the research method used in this paper.The results show that the prediction results of each subsystem are consistent with the qualitative analysis conclusions of a domestic design institute,that is,the fuel long cycle of a certain 650 MW nuclear power plant in China is qualified,and the paper establishes the reliability model and system reliability model.Correctness,and based on this,quantitative prediction of reliability,while considering several factors affecting reliability analysis(3)In the Qt Creator development environment,the C++ program for the reliability analysis of the system is written,including the algorithms of GME,MLE-SA,GM-MLE and DLSE,the comparison of the goodness of fit,and the goodness of fit of the KS method.Each safety subsystem is operated for a certain period of time to calculate the reliability.The program was tested by the example,and the reliability of each major equipment and the reliability of the subsystem were obtained.The results were consistent with the predetermined results,and the correctness and practicability of the program were verified.