Prioritization and Implementation Plan for Collaborative Case Study on RPV Steels During Extended Service

Nuclear power currently provides a significant fraction of the United States non-carbon emitting power generation. In future years, nuclear power must continue to generate a significant portion of the nation's electricity to meet the growing electricity demand, clean energy goals, and ensure energy independence. New reactors will be an essential part of the expansion of nuclear power. However, given limits on new builds imposed by economics and industrial capacity, the extended service of the existing fleet will also be required. Ensuring public safety and environmental protection is a prerequisite to all nuclear power plant operating and licensing decisions at all stages of reactor life. This includes the original license period of 40 years, the first license extension to 60 years, and certainly for any consideration of life beyond 60 years. For extended operating periods, it must be shown that adequate aging management programs are present or planned and that appropriate safety margins exist throughout the subsequent license renewal periods. Materials degradation can impact reactor reliability, availability, and potentially, safe operation. Components within a reactor must tolerate the harsh environment of high temperature water, stress, vibration, and/or an intense neutron field. Degradation of materials in this environment can lead to reduced performance, and in some cases, sudden failure. Clearly, understanding materials degradation and accounting for the effects of a reactor environment in operating and regulatory limits is essential. The Light Water Reactor Sustainability (LWRS) Program is designed to support the long-term operation (LTO) of existing domestic nuclear power generation with targeted collaborative research programs into areas beyond current short-term optimization opportunities. Within the LWRS program, two pathways have been initiated to perform research essential to informing relicensing decisions. The Materials Aging and Degradation Pathway is designed to help develop the scientific basis for understanding and predicting long-term environmental degradation behavior of materials in nuclear power plants and to provide data and methods to assess performance of systems, structures, and components essential to safe and sustained operation. The Risk-Informed Safety Margins Characterization Pathway (RISMC) seeks to merge fundamental scientific understanding of critical phenomenological conditions and deterministic predictions of nuclear power plant performance with risk-informed characterization tools. This will provide an integrated characterization of public safety margins in an optimization of nuclear safety, plant performance, and long-term asset management. Clearly, these two pathways have many synergies in goals and outcomes. The data and mechanisms generated in the Materials Pathway may feed into and mold efforts within the RISMC Pathway. In addition, insights from the characterization tools developed in RISMC tasks may inform materials testing needs and experiments. To demonstrate this potentially powerful interaction, a joint case study has been proposed and initiated. This document describes the initial planning for a coordinated study between the Materials and the RISMC Pathways. A brief description of each Pathway is presented along with a more detailed description of the needs and requirements of this collaborative task. A list of criteria for any case-study candidate are then listed, along with the rationale for choosing pressurized thermal shock as the prime candidate an inter-pathway collaboration. A proposed timeline and organization of future interactions on this subject area is also presented.