Using Technology to Support Proactive Management of Materials Degradation for the U.S. Nuclear Regulatory Commission

Abstract

The majority of the U.S. reactor fleet is applying for license renewal to extend the operating life from the current 40 years to 60 years, and there is now active interest in extending the operating life to beyond 60 years. Many plants are also applying for increases in power rating and both of these changes increases the need for an improved understanding of materials degradation. Many materials degrade over time and much is known about the degradation of materials under normal environmental conditions; however, less is known about the characteristics of materials degradation when the environment is subject to higher than normal radiological conditions over extended periods of time. Significant efforts are being made by industrial, academic and regulatory groups worldwide to identify, classify and mitigate potential problems arising from degradation of components in this context. From a regulatory perspective, the U.S. Nuclear Regulatory Commission (NRC) is very interested in being able to identify ways to ensure their licensees proactively manage the identification of materials degradation and the mitigation of its effects. To date, the NRC has consolidated “generic” programs for mitigating aging issues in the two volume Generic Aging Lessons Learned (GALL) Report (NUREG-1801) and has encouraged applicants for license renewal to use these programs where applicable in their plant when applying for renewal of their reactor’s license. The NRC has also published a comprehensive report entitled Expert Panel Report on Proactive Materials Degradation (NUREG/CR-6923) [3]. This report inventories the types of degradation mechanisms that could exist in each component of a light water reactor (LWR) and indicates how much is known about mitigating the effects within that context. Since the number of plant designs and materials used varies greatly within the U.S. fleet, there are many variations to implementing aging management programs (AMPs), requiring significant dialogs between the licensee and the NRC. These discussions are part of the licensing basis and as such are documented with up to multi-hundred page responses that are loosely coupled through the NRC Agency-wide Document Access and Management System (ADAMS). ADAMS serves as an electronic records repository for the NRC. These discussions have supported revisions to the GALL, including the revision that is being prepared as this paper is being written. The NRC has sought the help of the Pacific Northwest National Laboratory (PNNL) to improve their staff’s ability to navigate the significant numbers of documents that are generated in this process. PNNL is also to provide a forum for regulators, licensees, and researchers to share knowledge in their efforts to improve the cyclic process for defining, applying, validating, and re-defining AMPs. Work to date in this area is publicly accessible, and this paper will describe that work and outline a potential path forward. The presenter will also demonstrate the capabilities of the PMMD information tools (http://pmmd.pnl.gov).