Document: NRC Regulatory Guide
Document ID: 31f5b507-4290-458f-9233-049d79b5ff59
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:
nd may not be sufficient to detect all of the aging and other degradation mechanisms to which a particular cable is susceptible. While these tests can demonstrate the function of the cables under test conditions, they do not verify the continued successful performance of cables when called upon to operate fully loaded for extended periods, as they would under anticipated normal service operating conditions or under design-basis conditions. Nor does inservice testing of a cable provide specific information on the status of aging degradation processes or the physical integrity and dielectric strength of its insulation and jacket materials. Consequently, a cable circuit with undetected damaged or degraded insulation could pass an inservice functional test but still fail unexpectedly when called upon to operate under anticipated environmental conditions or the more severe stresses encountered in emergency operation during a design-basis event (i.e., fully loaded equipment, more extreme environmental conditions, extended operation in a heavily loaded state). Recent operating experience indicates inservice failures of several power cables. Longer cable circuits may pass through several different operating environments over the length of their routing throughout the plant. Portions of such a cable circuit may pass through areas experiencing harsh environmental conditions, such as high temperature, high radiation, high humidity, wetting (i.e., an operating environment in which a cable is exposed to moisture or high humidity for extended periods of time, with intermittent brief periods of complete submergence in water), or submersion (i.e., an operating environment in which a cable is completely submerged in water continuously or for extended periods of time). There has 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