Reliability Allocation And Risk Assessment Of Polar Cranes For Nuclear Power Based On Failure Analysis

As a key crane equipment during the maintenance of nuclear power plants,the polar cranes for nuclear power plants are mainly used for lifting the components of nuclear reactor such as the pressure vessel head,the reliability of its operation is directly related to the ability to accomplish the predetermined function and also affects the safety of nuclear power plants.In order to prevent the crane accident which possible causes serious consequences to the whole machine,nuclear environment and staff and meet the high reliability requirements,it is of great significance to carry out the research on the reliability allocation and risk assessment for polar cranes for nuclear power plants.In this paper,polar cranes for nuclear power plants is selected as the research object.Based on the clear realization of functions and structural division of polar cranes for nuclear power plants,firstly studies the possible potential failure modes,failure causes and failure effects of the circular cranes of nuclear power plants are studied,the corresponding failure mode and effects analysis(FMEA)table is established and the qualitative analysis is completed.Secondly,the influence of failure severity factor is considered,and a method is proposed to complete the comprehensive reliability allocation of polar cranes for nuclear power plants.Moreover,the complexity of polar cranes for nuclear power plants in risk assessment is considered,the test information of complete machine and environmental monitoring information are incorporated into the risk assessment framework,an updated model based on Bayesian network is constructed,and the idea of multi-source information fusion is introduced to obtain the updated information of the risk level of polar cranes for nuclear power plants.(1)Through the establishment of working schematic diagram and functional block diagram,the functional characteristics of polar cranes for nuclear power plants are clarified,the hierarchical structure of the whole machine is obtained,and the reliability concepts applying to the polar cranes for nuclear power plants are researched.On this basis,we also complete the FMEA work for the whole machine and put forward suggestions for improvement and compensation measures for weak links,and the failure mechanism of polar cranes for nuclear power plants is clarified,in order to further study of risk analysis and reliability allocation work.(2)Aiming at the problem that the whole machine index is difficult to be transformed into the reliability requirements of each constituent unit,a method based on non-linear transform functions of FMEA and possibility distribution function is proposed to obtain the interval-valued possibilistic mean values and the crisp possibilistic mean values of each subsystem under the failure severity factor.Then,considering the influence of many factors,the weight vector of subsystems is obtained through the reliability comprehensive allocation model under the multiple influence factors,finally the reliability comprehensive allocation is completed considering failure severity.(3)Aiming at the complexity of polar cranes for nuclear power plants,a risk assessment framework of updated model based on Bayesian network is constructed.At the same time,the test information of complete machine and environmental monitoring information of polar cranes for nuclear power plants are deeply excavated on the basis of failure analysis,the extension AHP method and fuzzy Set theory are used to quantitatively evaluates the weight and degree of membership of parameter information,the source of information for updated model is explained.Finally,the idea of multi-source information fusion is introduced to obtain the updated information of risk level of polar craned for nuclear power plants.At the same time,the tendency and characteristics of risk level of polar craned for nuclear power plants are obtained during service.