Document: NRC Regulatory Guide
Document ID: 9547afbc-5a01-4bff-a41f-8300f5ba922b
Document Type: regulatory_guide
Title: Condition Monitoring Techniques for Electric Cables Used in Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1007/ML100760364.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.218
CFR Part: 
CFR Title: 

Content:
been concern that such local adverse environmental stressors can cause excessive aging and degradation in the exposed sections of a cable that could significantly shorten its qualified life and cause unexpected early failures. It should be emphasized that the occurrence of cable system operating environments or locally adverse conditions that are unanticipated or more severe than the original plant design may constitute a DG-1240, Page 3 design deficiency of the cable system. A cable system must be designed to meet applicable regulations and to perform its intended function in the plant environment under all anticipated operational occurrences and design-basis events. Special consideration should be given to the problem of monitoring the operating environment for cable circuits routed through inaccessible underground cable ducts and conduits, covered cable distribution trenches, bunkers, and manhole vaults. Since most of these underground distribution systems are largely inaccessible, wetted and flooding conditions remain undetected for extended periods of time. Eventually, power and control cables that are not designed to operate in a submerged state will experience early failures, often resulting in significant safety consequences. The NRC has described several of these incidents in Information Notice 2002-12, “Submerged Safety-Related Cables,” dated April 21, 2002 (Ref. 3), Information Notice 1989-63, “Possible Submergence of Electric Circuits Located Above the Flood Level Because of Water Intrusion and Lack of Drainage,” dated September 5, 1989 (Ref. 4), and Generic Letter 2007-01, “Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients,” dated February 7, 2007 (Ref. 5). Generic Letter 2007-01 observed that cable insulation degradation as a result of continuous wetting or submergence could affect multiple underground power cable circuits at a plant site; should one of these medium-voltage