Key attributes of an effective plant life management programme include a focus on important SSCs which are susceptible to ageing degradation, a balance of proactive and reactive ageing management programmes, and a team approach that ensures the coordination of and communication between all relevant NPP and external programmes. Continued plant operation, including operation beyond design life (usually called long term operation), depends, among other things, on the physical condition of the plant. This is influenced significantly by the effectiveness of management ageing process.

Most HWR NPP owners/operators use a mix of maintenance, surveillance and inspection (MSI) programmes as the primary means of managing ageing. Often these programmes are experience-based and/or time-based and may not be optimized for detecting and/or managing ageing effects. From time-to-time, operational history has shown that this practice can be too reactive, as it leads to dealing with ageing effects (degradation of SSCs) after they have been detected. Reactive ageing management (i. e. repairing or replacing degraded components) may be cost effective for some, in particular, small replaceable components. However, for most important SSCs, utilizing proactive ageing management is generally most effective from both the safety and economic perspective.

Premature ageing of NPP SSCs implies ageing degradation that occurs earlier than expected. It can be caused by pre-service and service conditions (fabrication, installation, commissioning, operation, or maintenance) that are more severe or different than assumed in the design.

For instance, frequent pressure/ temperature transients, particularly those that have been not considered in the design basis, might lead to premature component fatigue. Even small changes, particularly those that affect the chemistry of the circuits, may induce premature degradation several months or years later. Excessive testing and/or routine maintenance can accelerate wear-out of components without additional benefit. Such conditions may not have been taken into account in the usual MSI programmes, unless there is a systematic and comprehensive assessment of ageing effects.

In many cases premature and/or undetected ageing cannot be traced back to one specific cause or an explicit error. The root cause is often a lack of communication, documentation and/or coordination during design, fabrication, commissioning, operation or maintenance. This lack of effective communication and interfacing frequently arises because, with the exception of major SSCs, such as the fuel channels or steam generators, there is a lack of explicit responsibility for achievement of specific SSC lifetime. Lack of effective communication and coordination can be remedied by the implementation of a systematic ageing management process.