ML17276B191
| ML17276B191 | |
| Person / Time | |
|---|---|
| Issue date: | 10/03/2017 |
| From: | Matthew Hiser, Amy Hull, Pat Purtscher, Ramuhalli P, Robert Tregoning Office of Nuclear Regulatory Research, Pacific Northwest National Laboratory |
| To: | |
| Matthew Hiser | |
| References | |
| Download: ML17276B191 (1) | |
Text
Harvesting of Aged Materials from Operating and Decommissioning Nuclear Power Plants M. Hisera, P. Purtschera, P. Ramuhallib, A. B. Hulla, and R. Tregoninga aU.S. Nuclear Regulatory Commission (NRC), Washington, D.C., USA bPacific Northwest National Laboratory (PNNL), Richland, WA, USA Background and Motivation Recent developments in the nuclear industry include stronger interest in extended plant operation and plans to shut down a number of nuclear power plants (NPPs). In the U.S.,
there is strong interest in extending NPP lifespans through subsequent license renewal (SLR) from 60 to 80 years.
Extended plant operation and SLR raise a number of technical issues that may require further research to understand and quantify aging mechanisms. U.S. utilities and the U.S.
Nuclear Regulatory Commission (NRC) have focused on the aging of systems, structures, and components and in particular four key SLR issues: reactor pressure vessel (RPV) embrittlement, irradiation-assisted stress corrosion cracking of reactor internals, concrete structures and containment degradation, and electrical cable qualification and condition assessment.
Meanwhile, in recent years, a number of NPPs, both in the U.S. and internationally, have shut down or announced plans to shut down for various reasons, including economic, political, and technical challenges. Unlike in the past when there were very few plants shutting down, these new developments provide opportunities for harvesting components that were aged in representative light water reactor (LWR) environments.
In a third related development, economic challenges and limited budgets have restricted the resources available to support new research, including harvesting programs. Given this constrained budget environment, aligning interests and leveraging with other organizations is important to allow maximum benefit and value for future research programs.
Potential Criteria for Harvesting Prioritization A number of criteria may be considered when prioritizing the data needs for harvesting, including:
Applicability of harvested material for addressing critical gaps Harvesting for critical gaps prioritized over less essential technical gaps.
Ease of laboratory replication of the degradation scenario For example, simultaneous thermal and irradiation conditions are difficult to replicate, and accelerated aging may not be feasible for a mechanism sensitive to dose rate.
Current Activities NRC has recently undertaken an effort, with the assistance of Pacific Northwest National Laboratory (PNNL), to develop a strategic approach to harvesting aged materials from NPPs. Due to limited opportunities, past harvesting efforts have been reactive to individual plants shutting down and beginning decommissioning. Given the expected availability of materials from numerous plants and anticipated research needs to better understand aging out to 80 years of operation, the NRC is pursuing a more proactive approach to prioritize the data needs best addressed by harvesting and identify the best sources of materials to address high-priority data needs for regulatory research.
The first step in this strategic approach is to prioritize data needs for harvesting. A data need describes a particular degradation scenario and should be defined with as much detail as appropriate in terms of the material (alloy, composition, etc.) and environment (temperature, fluence, chemistry, etc.).
The above potential criteria provide a systematic approach to prioritize data needs for harvesting. Different organizations may weigh and consider each of these criteria differently based on their interests and perspectives, but each criterion is likely relevant to some degree for any organization. NRC is interested in engaging with other organizations to prioritize data needs for harvesting and identify areas of common interest.
Harvesting Database The NRC is pursuing the development of a database for sources of materials for harvesting, which could include both previously harvested materials and those available for future harvesting. This database would allow for aligning of high-priority data needs to the available sources of materials. The level of detail for the database should be appropriate for the factors influencing decision-making. NRC is interested in engaging with other organizations in developing the database.
Path Forward NRCs experience is that harvesting can yield highly representative and valuable data on materials aging, but these efforts will be challenging. Having a clearly defined objective and early engagement with other stakeholders are keys to success. As specific harvesting opportunities are identified through this strategic approach, the NRC welcomes opportunities for cooperation and leveraging of resources with other interested research organizations.
Unique field aspects of degradation For example, unusual operating experience or legacy materials (fabrication methods, etc.) no longer available.
Fleet-wide vs. plant-specific applicability of data Greater value in addressing an issue applicable to a larger number of plants.
Harvesting cost and complexity For example, harvesting un-irradiated concrete or electrical cables less expensive and less complex than harvesting from the reactor internals or RPV.
Availability of reliable in-service inspection (ISI) techniques for the material / component If mature inspection methods exist and are easy to apply, harvesting may be less valuable.
Availability of materials for harvesting Timeliness of the expected research results relative to the objective.