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...

Dry cask storage systems (DCSSs) for used nuclear fuel were originally envisioned for storage periods of short duration (approximately a few decades). However, uncertainty challenges the opening of a permanent repository for used nuclear fuel, implying that used nuclear fuel will need to remain in dry storage for much longer durations than originally envisioned. Thus, aging degradation of DCSSs becomes an issue that may not have been sufficiently considered in the design phase and that can challenge the efficacy of very long-term storage of used nuclear fuel.

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.

In this effort, an assessment of bulk ultrasonic (UT) and eddy current (ECT) methods and techniques is performed for inspecting the surfaces of dry cask storage systems (DCSSs) canisters. Some DCSS canisters (especially those located in coastal environments) will be exposed to environmental conditions, which can cause atmospheric stress corrosion cracking (SCC). Information collected from the field and from laboratory studies has not been able to rule out the possibility of atmospheric SCC in DCSS canisters, although no occurrences of atmospheric SCC in DCSS canisters have been detected. UT and ECT methods and techniques are already used to inspect nuclear power plant components and this experience, along with their relative maturity, makes these methods and techniques likely frontrunners for near-term application to examination of dry storage canister surfaces. In this report, the results of several performance reliability studies for UT and ECT are reviewed. The detection, depth-sizing, and lengthsizing results are documented and summarized to quantitatively estimate the adequacy of UT and ECT for inspecting dry storage canister surfaces. In addition, this effort focuses on the implementation of NDE methods and techniques in the Holtec HI-STORM 100 system and the Transnuclear NUHOMS horizontal storage modules and considers environmental compatibility, accessibility constraints, and NDE sensor deployment options for these systems.v

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Prognostic health management technologies are expected to play a vital role in the deployment and safe, cost-effective operation of advanced reactors by providing the technical means for lifetime management of significant passive components and reactor internals. This report describes a Bayesian methodology for the prediction of remaining life of materials and passive AR components. This approach, previously applied to predict time-to-failure of materials subjected to localized aging and degradation, is adapted for component-level prognostics. The Bayesian framework for component-level prognostics incorporates the ability to fuse information from multiple sources, including information on localized degradation and component-level condition indicators. The ability to switch between multiple models of degradation accumulation rate and/or multiple models of measurement physics becomes important in this context, and a reversible jump Markov chain Monte Carlo methodology has been developed for this purpose. Evaluations of the Bayesian framework and the model switching and selection methodology were performed using synthetic data as well as experimental measurements on a high-temperature creep testbed. Results to date indicate that the feasibility of the proposed Bayesian framework for prognostics, though an improvement over previous methods' accuracy, will require the ability to quantify sources of uncertainties within the various models used in the prognostic framework. Ongoing efforts are focused on sensing and measurement (particularly in-situ measurements) that would be applied as inputs to the prognostics framework, with the objective of identifying measurement methods that can provide early indicators of material degradation and quantifying the reliability and sensitivity of these measurement methods.

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