Development of an In-Situ Method for Cable Condition Monitoring in Nuclear Power Plants

As nuclear power plants extend their operating life beyond 40 years, attention is being focused on the health of the insulation material of important cables. Faced with the prospect of an extremely expensive, wholesale replacement of thousands of miles of cables, nuclear facilities need a cost-effective, non-destructive, remote, and in-situ method to determine whether or not cables are healthy or should be replaced. While other products exist to identify conductor faults, there is no method available to assess the health and the remaining useful life (RUL) of the insulation material of installed cables. To address this problem, Frequency Domain Reflectometry (FDR), an in-situ non-destructive test, will be performed on cables typically used in the nuclear industry. These cables will undergo accelerated aging to simulate the natural aging process that occurs in a nuclear power plant. As they age, FDR measurements will be compared with a standard laboratory test known as elongation at break (EAB) to correlate the results and provide estimations of a cables health and RUL. During Phase I, a subset of nuclear power plant cables were thermally aged over the entire duration of the project. During this aging process, FDR measurements were compared to EAB results to assess insulation elasticity which is an industry-accepted measure of insulation health. The results demonstrated that FDR could be closely correlated to EAB. In Phase II, AMS will expand the research to include a larger population of cable types commonly found in nuclear power plants. Cable samples will be obtained and subjected to aging conditions while recording and correlating FDR measurements with the cable age. These correlations will be incorporated into a test system for nuclear facilities to assess the health of a cable and determine its RUL. Commercial Applications and OtherBenefits: The FDR correlations with cable health and RUL will be packaged with commercial hardware and custom software to provide a cost-effective solution for implementing a cable aging management program to satisfy regulatory guidelines. This system will identify and locate insulation problems and provide plant operators with a condition-based assessment of installed cable.