Design Of An Operator Support Expert System For Nuclear Power Plants

Nuclear power plant is an expensive and complex technology-intensive system with potential risk of radioactivity release. The loss and influence will be very serious once an accident occurs. A large number of engineering practices have indicated that human error is the major cause of nuclear incidents and accidents, both incorrect judgment and mis-action of the operators may lead to serious consequences.In this thesis, the domestic and foreign researches of operator support system were discussed. Based on theoretical investigation of condition monitoring, fault diagnosis,computer operation procedures and human-machine interface, this thesis proposed an approach to develop an operator support expert system for marine nuclear power plant which includes the functions of condition monitoring, alarm analysis, fault diagnosis and operation guidance. The operator support expert system is used to assist the operator in a series of activities such as plant condition monitoring, fault diagnosis and root cause identification,operation planning and operating procedure implementation. The main works of this thesis include:(1) The overall design scheme of operator support system were proposed according to the characteristics of the marine nuclear power plant, which provides guidance for the development of functional units.(2) A graphical modeling tool for constructing MFM (Multilevel Flow Model) was developed by the real-time expert system on the basis of summary of MFM reasoning rules.By the graphical tool the MFM of target system could be constructed easily and the alarm analysis and fault diagnosis knowledge base would be established. It makes the expert knowledge base easy to build, modify and expand.(3) Taking marine nuclear power plant as the research object, the MFM models of Reactor Coolant System. Pressure Safety System. Coolant Purification System and Residual Heat Removal System are modeled after function analysis. The alarm analysis knowledge base was constructed and the fault diagnosis knowledge base was constructed by combining FMEA (Failure Mode and Effect Analysis) with MFM further. Then, the intelligent alarm unit for analyzing and explaining the alarm events and the fault diagnosis unit for identifying the root cause of malfunction are established. Several typical faults and general faults were selected to validate the intelligence alarm unit and fault diagnosis unit afterwards.(4) An operation guide unit was designed to provide proper operation guidance to operators according to the status of nuclear power plant.(5) A human-machine interface was designed and developed based on the real-time expert system to achieve the display of information in a more effective and reasonable way,which can also assist operator understand the operational status of the nuclear power plant quickly and to identify failure cause under accident conditions accurately. Moreover, The hard panel monitoring unit designed can detect the error operation of the operator to prevent human error effectively.The design of real-time expert system for operator support system integrated the function of condition monitoring, alarm analysis, fault diagnosis and operation guide, which provide effective support for the operator. And the operator support system plays an important role in minimizing the workload and mental stress of the operator. Meanwhile, the human errors will be reduced. This thesis provides reference for further engineering application of operator support system.