Abstract
This study is part of the Nuclear Regulatory Commission's (NRC's) Proactive Materials Degradation Assessment (PMDA) program. The main objective was to identify materials and components where future degradation may occur in specific light water reactor (LWR) systems. The approach was to use a structured elicitation drawing on the knowledge of a panel of eight experts and the use of a Phenomena Identification and Ranking Table (PIRT) process. The international panel was given information on the materials, fabrication process, and operational environment for hundreds of different parts of systems in a Westinghouse four-loop design pressurized water reactor and a BWR-5 design boiling water reactor. They considered extensions to other designs as well. The panel developed metrics and used them to evaluate the susceptibility of given parts to different degradation mechanisms as well as the level of understanding for the varying degradation mechanisms for the given part. Inherent in arriving at these judgments of future behavior was an understanding of the prediction methodologies for the various degradation phenomena, calibrated by the component failures that have occurred in the past in the global LWR fleet. Also taken into account were the successes and limitations of mitigation/ control approaches that have been used to date. This report includes not only the panel's scoring and their rationale for it, and the conclusions derived from this process, but also considerable documentation of the relevant issues, the latter being found in appendices.

CITATION: Expert Panel Report on Proactive Materials Degradation Assessment (NUREG/CR-6923), Division of Fuel, Engineering, and Radiological Research, Office of Nuclear Regulatory Research, United States Nuclear Regulatory Commission, 2007.

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Expert Panel Report on Proactive Materials Degradation Assessment