Reliability Analysis Of Passive Residual Heat Removal System Under Ocean Conditions

Along with the continuous development of nuclear science and technology and the lessons learned from the three serious accidents of nuclear power plants,the domain of nuclear energy has put forward higher requirement of safety performance.Passive safety system has been adopted on more and more new-type reactors and marine nuclear power plants in order to enhance safety level.In theory,passive safety system has higher reliability,however,the lack of persuasive safety analysis report is an important reason which limits the large scale application of passive safety system.It has great significance for the development and application of nuclear energy to provide the safety analysis data of passive safety systems through scientific methods.The calculation of the probability of physical process failure is the key and difficult point of the reliability analysis of passive system.At present,there is no unified scientific analysis method of this issue in the world.Therefore,it is necessary to design a specific analysis program according to the different research objects and requirements.In this paper,aiming at the passive residual heat removal system of small-scale integrated PWR IP200 under ocean conditions,thermal hydraulic analysis and passive system reliability analysis method is combined to analyse and evaluate the functional reliability of passive residual heat removal system under black out accident.The purpose is to evaluate the reliability of the passive residual heat removal system of IP200 under the influence of ocean conditions more accurately and comprehensively.In this paper,physical reliability model of integrated PWR IP200 which takes the influence on the thermal-hydraulic characteristics introduced by ocean conditions into account is based on the best estimate program RELAP5/MOD3.1 platform.The first step is confirming the source of uncertainty.The next step is quantificating uncertainty by Monte Carlo method in order to simulate different ocean conditions.The physical reliability model is used to simulate the progress of black out accident,and then making use of PSA method in combination to calculate and analyse the reliability of passive residual heat removal system under black out accident.The calculation result shows that under the condition of black out accident,the passiveresidual heat removal system of the integrated PWR IP200 still could accomplish the function of deriving the residual heat of reactor core and maintaining the long-term cooling of reactor core under the influence of ocean conditions,and has extremely high reliability.