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:
1 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 cables fail, the resulting high-level fault currents and transient voltages would propagate onto the immediate power distribution system and potentially fail other systems with degraded power cable insulation. Operating experience reveals that the number of cable failures is increasing with plant age, and that cable failures are occurring within the plants’ 40-year licensing periods. These cable failures have resulted in plant transients and shutdowns, loss of safety functions and redundancy, entries into limiting conditions for operation, and challenges to plant operators. While in many cases the failed cables were identified through current testing practices, some of the failures may have occurred before the failed condition was identified (i.e., on cables that are not normally energized or tested). Therefore, it is necessary to monitor the condition of electric cables throughout their installed life through the implementation of a cable condition monitoring program. Condition monitoring involves the observation, measurement, and trending of one or more condition indicators that can be correlated to the physical condition or functional performance of the cable. An “ideal” condition monitoring technique should have the following desired attributes: a. nondestructive and nonintrusive, b. capable of measuring property changes or indicators that are trendable and can be consistently correlated to functional performance during normal service, c. applicable to cable types and materials commonly used in nuclear power plants, d. provides reproducible results that are not affected by the test environment or, if they are so affected, the results can be corrected for those effects, e. able to identify the location of any defects in the cable, f. allows the establishment