As the fleet of nuclear power plants (NPPs) approach their1 original qualified life (typically 40 years) and operators seek license extensions, regulators require assurance that they can continue to operate safely in the decades to come. Some of the most important, yet often overlooked components, are the cables that provide the signal paths for instrumentation and control (I&C) systems used to ensure safe and efficient operation of NPPs.In response to this, the authors explore the use of expanding indenter modulus (IM), an industry-accepted technique for cable condition monitoring, into a prognostic tool for predicting the remaining useful life (RUL) of I&C cables. Not only is this technique non-destructive, but it can be performed while NPP cables are in service, thus making it practical for adoption into existing cable condition monitoring programs. In this paper, the authors describe an accelerated aging cable test bed used to acquire several types of measurement parameters as cables age. Additionally, practical techniques are described in which simple IM measurements can be leveraged for condition monitoring and RUL estimation.Error analysis indicates the proposed method is superior to conventional RUL estimation techniques, such as simple trending and curve fitting. The authors demonstrate that using IM can potentially provide a non-destructive, in-situ estimation of RUL for I&C cables. As described in this paper, the IM data clearly shows trends as a function of cable age, and shows promising performance for RUL estimation especially compared with conventional techniques.

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.

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