Life Time Management: A Practical Approach of Nuclear Power Plants

Abstract

A comprehensive life time management has to take care of all safety and availability relevant components in nuclear power plants, with different intensity, of course. For instance, mechanical systems and components can be basically classified/ranked into three different groups: (1): The quality status of the components in this group has to be guaranteed on a pre-defined (high) level. (2): The quality status of the components in this group has to be maintained on its actual level. (3): Other components with no specific quality demands. Regarding the first group, integrity has to be guaranteed. Therefore it is necessary to monitor the possible root causes of degradation mechanisms during plant operation; thus the degradation effects can be assessed and — more important — controlled to maintain the safety standard on the demanded high level without any compromise. The monitoring of consequences of degradation mechanisms is being performed as an additional redundant measure. The requirements to maintain the quality status of the second group of components can be fulfilled by monitoring of the consequences of operational degradation mechanisms to be performed by preventive maintenance activities, in terms of tests, inspections and repairs, using either time dependant procedures or component condition orientated methods. For the third group of components, no preventive action is necessary. However, failures and malfunctions have to be assessed statistically to avoid a reduction of the required basic component quality. In the first two groups all safety relevant components and systems are included. Generally, aging management programs cover these two groups of components; life time management covers all of above groups. This paper concentrates on mechanical systems and components; it summarizes the practical approach to life time management as it is realized in German nuclear power plants. The application is discussed using dedicated examples.