Fault Modeling Of NPP Digital I&C System And Online Monitoring

Nuclear industry, whose wheel is controlled by nuclear safety as the foundation, is booming in China at the beginning of the 21st century. After the Fukushima Daiichi accident, IAEA calls for the countries who have NPP to review the Nuclear Regulatory on safety. NASA has Jointed related departments in accordance with the requirements of the state council to carry out a comprehensive safety inspection of nuclear power plant, and to review the situation that NPPmeet the current laws and regulations, standards, and ability to cope with Fukushima similar external events.The instrument & control(I&C) system plays an important role in keeping the NPP operate safety, reliably and economically. With the advent of the computer age, digital I&C system has been widely used and gained the full scope of control of NPP, then become the central nervous of nuclear station. So regular functional maintenance of the system and timely troubleshooting is a must to ensure the reliability of I&C system equipment to guarantee the stable operation of the digital I&C system According to the actual needs of the plant, risk assessment is given to the NPP I&C system as a theory basis maintenance decision.At present, most power plants just give alarm to the failure of the equipment, and implement maintenance and repair of equpment according to the alarm without the risk assessment. In this paper, we developed an expert maintenance support system to make up for the deficiency the risk assessment according to the needs of the project from CGN. And we choose A nuclear power station unit 3 I&C system as research object, give the this nuclear station digital I&C system careful study. According to the unit 3 digital I&C system’s design book, a fault tree(FT) with KIC alarm as top event has been built. We use VPLANT as Calculation engine to complete the assessment to assist the NPP manager make decision. After the completion of the fault tree, the graphical navigation system then can show the specific address of the hazards in the map of the plant according to the fault tree location information. And some expert opinions were given in each level’s fault node to Improve the efficiency of maintenance work.According to the mentioned above, we have developed special fault tree module which is accordance with the requirements of the system function, and built alarm FTs. At the same time, we have developed the corresponding data base to storage the modules’state information, and drew maps of the graphical navigation system Finally, link the fault tree and graphical navigation system to the data base to unit fault location and the map guide.