The generic term of SMP assessments is used to reflect a number of assessment techniques most commonly referred to as reliability centered maintenance (RCM), streamlined RCM (SRCM), and preventive maintenance optimization (PMO).

This systematic assessment, combined with input from the various specialists, provides elements for establishing the maintenance basis as described in INPO AP-913 “Equipment Reliability guideline” that is becoming widely used in the nuclear industry. The goals of these assessments are:

• To develop a documented technical basis for the overall maintenance strategy associated with each component considered. This provides the foundation for a programme that is adaptive throughout the life of the plant.

• To ensure that a sufficiently comprehensive maintenance strategy is applied to components to achieve the safety and operational goals of the plant.

These goals have a significant impact on the choice of assessment technique. Users need to assure themselves that the assessment process they choose will not result in insufficient maintenance being specified. There is a real possibility, through the application of various assumptions inherent in some techniques, to specify incomplete or ineffective maintenance. Similarly, regardless of the rigor inherent in a given technique, there is the potential to make non-conservative decisions while attempting to streamline or reduce the overall effort.

In addition, these techniques provide the opportunity to refine the maintenance strategy for each component in order that a plant might optimize the maintenance plan such that only the right maintenance is performed on the right component at the right time.

There are several methods or approaches to applying these techniques. The key is that the process be systematic and rigorous and address the goals noted above. Whether done by single assessors, teams led by facilitators, or expert panels, they need to always follow the same overall process. This includes documenting the results and providing sufficient background to understand the basis of the maintenance strategy to be implemented. This basis needs to include an understanding of the components functions within the context of the system and the systems function within the plant.

The application of SMP assessments does allow for plants to focus on areas of highest risk first, especially when working with limited resources, while meeting the goals above. The system screening provides a focus on more critical systems. Within the system assessments, further focus can be achieved through the inclusion of a criticality evaluation step, typically a feature of streamlined techniques and part of the INPO AP-913 process. The criticality evaluation can be simplified through focus on major components within a system. The criticality is based upon the failure effects attributed to the component.

Other simplifying techniques, such as applying a maintenance strategy, as developed for one component, to group of similar components, is not uncommon, but is a practice that needs to be carried out carefully. Even if the component for which the strategy has been developed is highly critical, the context of operation (e. g. system function) and environmental considerations need to be applicable to the entire group. Assurance is needed that the failure modes of interest are common across the entire group of components. These cautions derive

from the intent of meeting the goals given above. The following are some examples of CANDU 6 systems have been assessed using this technology:

• Four containment systems (dousing, containment isolation, airlocks, Class III local air coolers);

• Auxiliary and main feedwater and condensate systems;

• Class III standby and emergency power supply diesel generators and auxiliaries;

• Emergency core cooling;

• Instrument air;

• Moderator and auxiliaries;

• Main heat transport and auxiliaries; and

• Shutdown cooling systems.