Lab Studies Examine New Technique for Assessing Nuclear Plant Cables

EPRI is investigating a promising technology to evaluate the condition of low-voltage cables in nuclear plants—an historically difficult task.

Low-voltage cables serve important roles in nuclear plant operations, powering components, control systems, and communications. Many low-voltage cables were manufactured in the 1970s and 1980s, when most U.S. nuclear plants were built. As plant operators consider extending licenses beyond 30, 40, or 60 years, it is important to assess cables’ remaining useful life and to determine necessary repairs and replacements.

Today, technicians primarily use visual inspection and nonelectrical techniques. These require cable samples or direct access to cables, which is not always feasible. The best available electrical test method, frequency domain reflectometry, is performed at cable terminations. It can detect and locate anomalies but cannot determine whether anomalies result from degradation or bent or twisted cable.

Because prior EPRI research determined that dielectric spectroscopy is effective for assessing a cable’s overall condition, researchers wanted to determine whether it could be combined with frequency domain reflectometry to pinpoint areas of severe degradation requiring repair or replacement.

In the laboratory, they applied dielectric spectroscopy to three cable samples (both shielded and unshielded) before and during accelerated thermal aging, and the method showed promise in detecting degradation. Building on these results, EPRI plans to lab-test more cables, develop diagnostic metrics, and field-test naturally aged cables.

Artwork by James Provost

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