Research And Application Of Evaluation Method Of The Safety Injection System's Reliability

The core fuel extension cycle is an important work being carried out for nuclear power units.Under the condition of ensuring the safety of the unit,the existing method is to compare the historical data and draw the conclusion of core life prolonging,so as to improve the economic performance of the units.At present,there are few literatures to study the core life extension.On the basis of the existing historical data,this paper establishes the reliability model to study the feasibility of the core life extension,and provides the theoretical basis for the current core fuel extension cycle.Based on the nuclear power professional knowledge,reliability modeling theory and error theory,the security injection system is taken as an example to carry out related research work.The mian details are as follow:(1)Based on the Weibull distribution as the theoretical basis,the reliability model of the system equipment is constructed for the safety injection system of a PWR nuclear power unit in China.By means of bilinear regression,maximum likelihood estimation,support vector machine and gray estimation method,the model parameters of the equipment in the safety injectedsystem such as check valve,equipment system valve,high pressure injection pump,low pressure injection pump,flow control valve,are estimated by the failure data history of the equipment.The estimated values of equipment parameters under different methods are obtained.The cumulative failure probability values of the model are calculated,then based on the error theory,the mean value E and the standard deviation a of the deviation between the probability value and the observed value are calculated.By comparing the E and a of the two,the model error result is less than 5%,and the rationality of the system equipment reliability model parameters is verified statistically.The reliability and failure rate of the safety injection system are obtained.In order to ensure the accuracy of the model,compared with the existing evaluation methods,the rationality of the failure rate of the equipment-level reliability model is verified,which is in good agreement with the historical failure rate.(2)According to the characteristics of the safety injection system and the characteristics of the series,parallel,side and r/n(G)models,the reliability model of the high-pressure injection system,the reliability model of the medium-pressure injection system and the reliability model of the low-voltage injection system are constructed.The reliability of the three systems is calculated and predicted according to the reliability of the equipment.The results compared with historical values show that thehot and cold injection stage of HHSI,MHSI,the direct injection stage of LHSI,the recycle cold injection stage of LHSI are in accordance with the results of a long cycle of nuclear fueldemonstration.That is to say,the reliability of these stages in the safety injection system can reach the requirements of nuclear power operation in 18 months,which verifies the correctness and feasibility of the reliability model of these stages,on the other hand,thedirect injection stage ofLHSI,the hot and cold injection stage ofLHSI are against with the actual field value,the result shows that in the normal refueling cycle(12 months)is in line with the historical value,but in 12 to 18 months is lower than the actual re liability.The accuracy of the safety injection system reliability model is verified to a certain extent.(3)The software of the reliability of equipment in the safety injection system is prepared running in the matlab environment,the software can implement some features such as parameters input,output and data fitting,iteration and graph.and the software has been tested,and the result can be calculated.The result is consistent with the measured values which verifies the model and the feasibility of reconstruction software...