1 Westinghouse Energy Systems Europe

Life cycle management (LCM) has now been a priority issue in the US nuclear industry for many years. Extensive programs on the aging of nuclear power plants, specifically aimed at assessing the technical feasibility of plant life extension (formalized as ‘License Renewal’ in the US) have been performed. Plant Life Extension (PLEX) and LCM programs are now ongoing worldwide.

A Westinghouse Owners Group (WOG) program was initiated in 1993, to address cost-effective aging management as well as to establish a consistent approach to license renewal (LR) for WOG plants. The program is referred to as the LCM/LR program. The WOG is a utility organization comprising 24 domestic and 8 international utilities.

Since the US LR rule was first issued in 1990, the nuclear industry led by the Nuclear Energy Institute (NEI) has worked with the US NRC to understand the LR requirements and improve the predictability and cost-effectiveness of license renewal through simplifications to the original LR rule. The WOG has actively participated in this effort. The rule has been revised and was reissued in 1995. The need for detailed mechanistic aging evaluations for a large number of components was eliminated and replaced by a need to demonstrate aging management which would assure equipment ‘intended’ function. In particular, the implementation of the Maintenance Rule (MR) was credited to assure intended functions of active components. Aging management reviews as part of the LR rule are now limited to passive functions of components which are long-lived. The MR implies that performance goals be set for plant systems and components, and that monitoring is put in place to verify that performance goals are met.

One deliverable of the WOG LCM/LR program is a set of Generic Technical Reports for major components or component groupings in the scope of the LR rule (the above passive long-lived components). Generic Technical Reports are intended to establish a firm technical basis for implementing aging management programs and to be referenced by individual licensees as part of their plant specific LR applications. Aging management programs are described in the GTRs for the applicable components, providing alternative aging management programs such as 1) current or enhanced plant maintenance, inspection and testing programs, 2) diagnostic and monitoring (D&M) programs for assessing component/structure condition, and 3) analysis for component life prediction.

Nuclear power plant utilities are faced, in the US and worldwide, with increasing pressure to be cost-effective. In the economic equation, the question whether to pursue plant life extension (PLEX) is important. To address the question of PLEX, major investments required specifically for PLEX must be identified, such as major component repairs or replacements, based on aging models and component life predictions. Given the uncertainty associated with the actual aging effects, probabilistic decision analysis techniques are being applied to optimize PLEX investment planning and associated uncertainties.

Evolving programs to reduce costs of current and future nuclear power plant operation, are also categorized as part of LCM. Such programs include maintenance optimization and risk-based technologies. Such optimization programs are considered part of LCM for two reasons: 1) significant cost reductions from such programs can be obtained; 2) such programs help to provide the technical support for documenting the adequacy of aging management programs; 3) techniques used for these programs are similar or identical to techniques used for implementing regulation-driven programs such as the License Renewal and Maintenance rules described above.

In summary, three types of requirements apply to PLEX/LCM: