Guidance for optimizing nuclear power plant maintenance programmes. Report prepared within the framework of the Technical Working Group on Life Management of Nuclear Power Plants

Current changes in the electricity industry in many countries, such as market liberalization and privatisation processes, have led to a highly competitive market environment. The well managed nuclear power plants (NPPs), with their low fuel costs and permanently declining operation and maintenance costs, are often among the least expensive base load power plants to operate. In a competitive regime this situation encourages, but also forces NPP owners to further reduce their operation and maintenance costs, but of course without compromising safety which is, as always, a paramount consideration. Since the primary purpose of NPP maintenance is to allow nuclear operators to use all those functions necessary for safe and reliable power production by keeping them available, an adequate maintenance programme is essential. The maintenance programme covers all preventive and remedial measures, both administrative and technical, necessary to identify and mitigate degradation of a functioning system, structure or component, or restore the design functions of a failed system, structure or component to an acceptable level. Maintenance activities include servicing, overhaul, repair and replacement of parts and may, as appropriate, include testing, calibration and in-service inspection. As plants strive to reduce costs and increase equipment reliability, it becomes necessary to be sure that the right tasks are being performed on the right equipment. Many differing techniques are used to decide what work to do and many of these techniques create unnecessary expenses and take equipment out of service at the wrong times. When equipment fails to function or causes system or plant outages, one of the first impulses for corrective actions is to increase the number of predefined maintenance tasks (preventive maintenance) and increase the frequency of the tasks that have already been established. Many of these actions may cause more failures and decrease the overall plant reliability. A systematic evaluation approach to establishing what maintenance tasks are to be performed on which systems, structures or components and at what frequency, however, can optimize the use of resources (maintenance costs, personnel doses, equipment and tools, competent personnel, etc.) allocated for maintenance and plant availability. In addition, a systematic method of prioritizing which systems should be worked on and what combination of systems can be worked on at the same time. This approach can be used in establishing a preventive maintenance programme and for the optimization of the ongoing maintenance programmes. The process seeks to make the best use of condition-based maintenance where unnecessarily costly maintenance actions and associated maintenance error induced failures can be avoided. If a probabilistic risk assessment has been performed, its result can be used to help define the important systems and components. This optimization process can lead to the achievement of nearly all maintenance targets concerning safety, reliability and cost. The objective of the project on Optimization of Nuclear Power Plant Overall Performance within the IAEA's subprogramme on Nuclear Power Planning, Implementation and Performance is to systematically improve the overall performance and competitiveness of nuclear power plants with due regard to safety through the application of technological and engineering best practices, including quality assurance/quality management, and the utilization of relevant databases. As an integrated part of this project, the Technical Working Group on Life Management of Nuclear Power Plants deals with the managerial and engineering aspects of NPP maintenance; its optimization process, with special regard to the importance of condition monitoring in maintenance strategies; and the contribution of maintenance to managing lifetime of operating NPPs