Frequency domain reflectometry for remaining useful life estimation of instrumentation and control cables

As the existing fleets of nuclear power plants age, a greater emphasis has been placed on technologies to quantify the remaining useful life of safety-critical components and to ensure that these systems will operate as intended when called upon, especially in emergency situations. Some of the most important, yet often overlooked components, are the cables that provide the signal paths for instrumentation and control systems used to ensure safe and efficient operation of nuclear power plants. Instrumentation and control cable aging, in particular, is primarily concerned with degradation of the polymer material by thermal oxidation while exposed to heat, humidity, radiation, and other environmental stressors. Consequently, as the polymer becomes embrittled, it cracks and becomes susceptible to moisture intrusion that can cause shorts and shunts in the cable circuits. This article describes the development of two prognostic models to estimate the remaining useful life of nuclear power plant cables. The first model uses data compiled in an existing polymer aging database as background for introducing the remaining useful life model development methodology. The second model uses data generated from accelerated cable aging experiments performed by the authors and explores the use of in situ electrical measurements such as frequency domain reflectometry for predicting the remaining useful life of instrumentation and control cables typically found in nuclear power plants.