A Method Framework For Screening Safety-Related Human Actions In Nuclear Power Plants

For the safety and reliability,the design and operation of nuclear power plants(NPPs)need to follow the relevant principles of human factors engineering.Mainly consider the twelve elements of human factors engineering during the design phase of the NPPs.Human reliability analysis(HRA)is an important part.HRA includes two parts: qualitative analysis and quantitative analysis.They are equally important for human reliability analysis.However,more attention is paid to the results of quantitative analysis in the application process.Qualitative analysis is often ignored or used only as a process of quantitative analysis.In 2012,the U.S.Nuclear Regulatory Commission(NRC)amended the section of HRA in the Human Factors Engineering Program Review Model(NUREG-0711),Version 3,and renamed the chapter 7 as Treatment of Important Human Actions to emphasize the importance of qualitative analysis.This chapter proposes a detailed analysis of human actions so as to reduce human errors.Different personnel behaviors have different effects on the safe operation of nuclear power plants.Considering there are plenty of different human actions in the NPPs,so,it is necessary to screen the safety-related human actions and identify its corresponding risk level.The screening of human actions not only can effectively improve design work efficiency,but also can provide priority ranking to optimize human-system interaction design.More importantly,this can ensure that the safety-related human action has not been omitted.In the past,NPPs used probabilistic method,based on the probabilistic safety assessment,to screening human actions.In the process of screening for human actions,the key issue is to choose the appropriate risk boundary value.However,the risk boundary value directly used the value in selection of machine.Considering the huge difference between people and machines,this application is not rigorous enough.Moreover,the application of the probabilistic screening method to the screening of human actions do not fundamentally solve the problems caused by the uncertainty of the probabilistic screening method.Therefore,this paper has established a new human actions screening framework based on the previous screening methods,combined with probabilistic safety assessment and determination safety analysis of NPPs.The probabilistic screening method based on probabilistic safety assessment is an improvement over previous methods of probabilistic screening.This paper analyzes and discusses the importance measures used in previous screenings: Fussell-Vesely(FV)applies to human actions screening,and risk achievement worth(RAW)does not apply to human actions screening.In order to solve this problem,the concept of Human Action Risk Achievement Worth(HRAW)is introduced in human actions screening.This paper discusses this value and determines the method for selecting the risk boundary value in human actions screening.Then,combined with FV,a new method of screening for human action probabilistic theory was established.Deterministic screening method is based on NPPs deterministic safety analysis.This paper first reviews the related concepts of deterministic safety analysis in NPPs.Based on this,two appropriate standards,time and function of performing the action,are selected for human action selected.Afterwards,the method of human actions identification and acquisition for NPPs was clarified,and a screening process for the determinism of human actions were established.The deterministic screening method selected a unified standard to screen the human actions and ensured the traceability of the screening results.Finally,this paper combines the probabilistic screening method and the deterministic screening method to establish a screening framework for screening human action in NPPs.The framework solves the problems existing in the past using probabilistic screening method and ensures the completeness of the screening results.The method framework has been applied in nuclear power plants and has achieved good practice.For further explanation,this paper uses a nuclear power plant as an example to apply the framework and analyzes the screening results.The screening results prove that the framework has good applicability and sensitivity in screening human action.