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This milestone report presents an update on the state-of-the-art review and research being conducted to identify key indicators of cable aging at nuclear power plants (NPPs), and devise in-situ measurement techniques that are sensitive to these key indicators. The motivation for this study stems from the need to address open questions related to nondestructive evaluation (NDE) of aging cables for degradation detection and estimation of condition-based remaining service life. These questions arise within the context of a second round of license extension for NPPs that would extend the operating license from 60 to 80 years. Within the introduction, a review of recent published U.S. and international research and guidance for cable aging management programs including NDE technologies is provided. As with any "state-of-the-art" report, the observations are deemed accurate as of the publication date but cannot anticipate evolution of the technology. Moreover, readers are advised that research and development of cable NDE technology is an ongoing issue of global concern.Cable safety factors offer significant margin for normal operation and consequently most cables can be expected to perform satisfactorily under normal loads. Cables are inherently tested as part of the regular system tests that are periodically performed on nuclear plant systems and active components. As emphasized in Regulatory Guide 1.128, the cable aging management program focuses on the ability of a cable to withstand extreme stresses such as in a design-basis event (DBE) that may not be addressed with normal system tests. Degradation of the electrical insulation and other cable components are key issues that are likely to affect the ability of the currently installed cables to operate safely and reliably under a DBE for another 20 to 40 years beyond the initial qualified operating life. With more than 1000 km of power, control, instrumentation, and other cables typically found in a NPP, it would be a daunting undertaking to inspect all of the cables. Practical guidelines, however, have been developed and are evolving that offer a manageable approach to sampling and screening cables based on accessibility, risk, history, and other factors. Moreover, the range of cables and conditions plus today's state of the art does not support a single test to assure the cable's function. Rather, a range of testing tools must be applied to manage the cable aging concerns and assure that degraded cables are repaired or replaced prior to the end of their safe operating life. Cable aging management program recommendations include a database of cables selected for test and trending including the required appropriate cable test based on accessibility, risk, and environment. Such tests include bulk electrical characteristic measurements that can be made from the cable ends and, in some cases, locate the weak portion of the cable as well as local tests to confirm insulation condition and provide guidance to predict remaining available safe life.The Pacific Northwest Nat...

Executive SummaryThe motivation for this study stems from the need to address the aging management of incontainment cables at nuclear power plants (NPPs). The most important criterion for cable performance is its ability to withstand a design-basis accident. With nearly 1000 km of power, control, instrumentation, and other cables typically found in a NPP, it would be a significant undertaking to inspect all of the cables. Degradation of the cable jacket, electrical insulation, and other cable components is a key issue that is likely to affect the ability of the currently installed cables to operate safely and reliably for another 20 to 40 years beyond the initial operating life. The development of one or more nondestructive evaluation (NDE) techniques and supporting models that could assist in determining the remaining life expectancy of cables or their current degradation state would be of significant interest. The ability to nondestructively determine material and electrical properties of cable jackets and insulation without disturbing the cables or connections has been deemed essential.Currently, the only technique accepted by industry to measure cable elasticity (the gold standard for determining cable insulation degradation) is the indentation measurement. All other NDE techniques are used to find flaws in the cable and do not provide information to determine the current health or life expectancy.There is no single NDE technique that can satisfy all of the requirements needed for making a lifeexpectancy determination, but a wide range of methods have been evaluated for use in NPPs as part of a continuous evaluation program. The commonly used methods are indentation and visual inspection, but these are only suitable for easily accessible cables. Several NDE methodologies using electrical techniques are in use today for flaw detection but there are none that can predict the life of a cable.There are, however, several physical and chemical property changes in cable insulation as a result of thermal and radiation damage. In principle, these properties may be targets for advanced NDE methods to provide early warning of aging and degradation. Examples of such key indicators include changes in chemical structure, mechanical modulus, and dielectric permittivity. While some of these indicators are the basis of currently used technologies, there is a need to increase the volume of cable that may be inspected with a single measurement, and if possible, to develop techniques for in-situ inspection (i.e., while the cable is in operation). This is the focus of the present report.Several approaches to nondestructively measuring key indicators of cable aging and degradation may be available, and could include chemical, mechanical, and electrical measurements. Electrical and acoustic measurements are potential alternative NDE approaches that may be capable of providing in-situ assessments of cable condition and remaining useful life.Measurement studies were conducted with samples of aged ethylene propylene rubber (EPR) cabl...

Director. Additionally, PNNL recognizes Mr. Tom Sowinski as the DOE Technical Manager and Mr. Carl Sink as the HQ Program Director. PNNL would like to thank Mr. Grandy for his guidance and technical direction throughout the course of this effort. The Technical Team would also like to thank our colleagues at ANL for working jointly with PNNL staff over the course of this collaborative effort. At PNNL, the authors wish to thank Ms. Katie Holton for her coordination and support of PNNL project logistics and for her help in handling travel-related reporting. The Team is indebted to Mr. Royce Mathews (also a co-author on this TLR) for providing in-Lab support across the entire spectrum of technical activities conducted on this project. In addition, the Team would like to express their thanks to Mr. Clyde Chamberlin, who was very responsive to our needs as we required his expertise in developing and employing an effective procedure for polishing the faceplate of the prototype probes, prior to insodium testing. The Team would also like to extend their gratitude to Ms. Lori Bisping for all of her hard work in providing administrative and financial reporting support to this project. Working with the PICS system can be challenging, and Lori's expertise and efficiency are second to none. Finally, the PNNL technical team would like to extend their thanks to Ms. Kay Hass for her ongoing support, attention to detail, and technical editing expertise in preparing and finalizing this Technical Letter Report.

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