Updated Aging Assessment Approach and Use with Electric Cable Insulation

Abstract

The service life of nuclear power plant equipment may include operation beyond the original design or qualified life. A technical basis is necessary to demonstrate that critical equipment is capable of continued safe operation for any life extension and renewed license term. Such a technical basis is also useful in addressing initial license term aging degradation, age-related failures, and maintenance issues. Early approaches for addressing aging effects developed for environmental qualification programs in the 1980s were incorporated into the Institute of Electrical and Electronic Engineers’ (IEEE) IEEE Std. 1205-1993. However, subsequently, a number of events (including promulgation of the Maintenance Renewal Rule, the new License Renewal Rule, and initial plant owner submittals of License Renewal applications) have resulted in improved aging management approaches, which focus on addressing aging effects rather than attempting to identify and mitigate every possible aging mechanism.An example of a major issue facing nuclear power plants as they mature is the general health of the plant electrical cables. This issue came to the forefront as plants began preparing for license renewal, which requires an evaluation of cables to demonstrate that they will perform their function 20 yr beyond the original 40-yr license period. When the two lead plants started preparing for license renewal, there was no generally accepted approach to the bulk evaluation of plant cables, and there were many who thought it not possible to perform a complete plant cable evaluation. The approaches that emerged from the lead plant reviews demonstrated that an assessment of the general health of plant cables could be performed.IEEE’s Nuclear Power Engineering Committee recognized the need to capture these improved approaches. A 2½-yr effort of the IEEE Subcommittee-3 Working Group 3.4 culminating in IEEE Std. 1205-2000 is the consensus of representatives from the two lead license renewal plants (Calvert Cliffs and Oconee), the Nuclear Regulatory Commission, a national laboratory, other utilities, and multiple engineering/consulting firms. This revision, now complete, updated the Guide to incorporate the aging assessment methods used by the two lead license renewal plants and the experience gained by the industry and the regulator and, in addition, added an example annex applying the guidance to electrical cable, and both are summarized in this paper.