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:
hardness) technique that is applicable to polymer jacket and insulation materials, such as polyethylene, EPR, chlorosulphonated polyethylene, and neoprene, used for low-voltage cables. The compressive modulus technique is most effective at detecting thermally induced embrittlement and radiation-induced embrittlement. The technique can detect and monitor the stressor effects of elevated temperature and radiation exposure. Advantages of the compressive modulus test are that it is relatively easy to perform, it provides trendable data on commonly used cable insulation materials, and results can be correlated to known measures of cable condition. This technique is suitable for assessing short segments of the insulation. The disadvantages are that the cables must be accessible for in situ measurements; measurements are made on the outer surface so the condition of underlying insulation must be inferred; the underlying cable construction, cable geometry, temperature, and humidity affect the results; aging-related changes in the compressive modulus are very small for some polymers until the end of life; the compressive modulus does not give direct correlation to changes in electrical properties (such as insulation resistance and dielectric strength); and the test is not effective for XLPE cables that do not have a polyethylene jacket. 6. Dielectric Loss-Dissipation Factor/Power Factor The dielectric loss-dissipation factor or power factor test (tan δ test) can be used to diagnose problems in low- and medium-voltage cables. The dielectric loss-dissipation factor test has the ability to detect thermally induced cracking, radiation-induced cracking, mechanical damage, water treeing, moisture intrusion, and surface contamination. Advantages associated with the dielectric loss-dissipation factor technique are that it is relatively easy to perform, it provides trendable data on commonly used cable insulation materials, it does not require access to the entire cable, and the