Based On Fault Tree Experimental Fast Reactor Nuclear Grade Circulating Cooling Water System Reliability Analysis And Partial Dynamic Problems

China Experimental Fast Reactor (CEFR) is the first sodium-cooled fastreactor of China. It is significant for the development of energy strategyof our country.Nowadays, the Probabilistic Safety Assessment (PSA) of CEFR isundertaking, of which reliability analysis of safety system is a importantpart. In this paper, fault tree analysis on the cooling water system of CEFRfor the reliability assessment is completed. Meantime, study of the questionin-depth that traditional fault tree method cannot handle the dynamic problemwell, and acquire the result which is more close to the reality.The function of the cooling water system is exporting the heat releasedby the equipments in the nuclear island. The reliability of the system isconcern with the normal operation of the reactor. The system consists of twocirculating water pumps, four supply pumps, two cooling towers and relatedcontrol system. And the control system which is very complex involves a seriesof movements, such as mutual standby of two pumps, automatic or manual input,startup of the pumps with the control of water level, and so on. The finalresults shows that the unavailability of the system is 9.21×10^-4. And thatthe two circulating water pump fail at the same time is the biggest riskcontributor.This system contains many standby systems and basic components whosefailure rate is not constant. Traditional fault tree which uses steady-stateanalysis cannot deal with the problem which contains sequential logic changeor muti-state of basic events, because of its limitation. This paper adoptsthe modular idea, separates the part which contain the standby pumps, and usesMonte-Carlo method to calculate its unavailability. Meantime, resolve theproblem of inconstant failure rate of events by introducing the Weibulldistribution. Then instead of the corresponding part in static fault tree with the results figured out before, calculate the system unavailability again,and compare with the previous results.This paper uses Monte-Carlo method to handle the standby system problemand resolve the problem of inconstant failure rate of events by introducingthe Weibull distribution. Then, certifies the program through a simple system,compares the method proposed in the text with the traditional means, analysisof the advantages and disadvantages of the program.It is the first time to complete the reliability analysis of CEFRnuclear-related equipments cooling water system, obtain the systemreliability parameters and the combination of failure events which makes mostcontribution to the unavailability of system. Not only give advices toimprovement of system design and optimization of operation, but also makeimportant contribution to CEFR Probability Safety Assessment. In this process,creatively bring the Monte-Carlo method and Weibull distribution to thereactor system reliability assessment basing on the fault tree technology,undertake the complementary exploration for system reliability analyzing withfault tree method.