Draft Report for Comment: Identification and Prioritization of the Technical Information Needs Affecting Potential Regulation of Extended Storage and Transportation of Spent Nuclear Fuel

he U.S. Nuclear Regulatory Commission (NRC) regulates storage of spent nuclear fuel (SNF) from commercial nuclear power plants. An increasing amount of the SNF in storage is in dry storage systems, mostly at current and decommissioned plants. As directed by the Commission (in SRM-COMSECY-10-0007; December 6, 2010), in expectation of continued use of dry storage for extended periods of time, the NRC staff is examining the technical needs and potential changes to the regulatory framework that may be needed to continue licensing of SNF storage over periods beyond 120 years. This report presents the results of NRC staff evaluation of the technical information needs for continued extended dry storage, and for the subsequent transportation of SNF following long-term storage. Staff’s evaluation focuses on the degradation phenomena that may affect dry storage systems, and how these phenomena may affect the ability of the systems to fulfill their regulatory functions.
The evaluation in this report focuses on technical information for safety of dry storage systems. Staff will also be evaluating potential security implication of extended storage and transportation (EST) as part of its broader work in this area. The NRC is currently revising parts of its regulations on physical protection in 10 CFR Part 73 that pertain to storage of SNF (Draft Technical Basis for Rulemaking Revising Security Requirements for Facilities Storing SNF and HLW; Notice of Availability and Solicitation of Public Comments, 74 Fed. Reg. 66589, December 16, 2009). Any additional revisions to security regulations that may be needed to address extended storage and transportation will be considered when the current rulemaking for 10 CFR Part 73 is complete, or as new needs are identified.
In identifying and prioritizing potential information needs, NRC staff drew on existing published assessments on the behavior of SNF in storage and the degradation phenomena for dry storage systems, and on staff knowledge and experience in reviewing and licensing dry storage installations and certifying systems for storage and transportation under current regulations
(10 CFR Part 72 and 10 CFR Part 71, respectively). For each of the major systems, structures, and components (SSCs) of a dry cask storage system, a set of potential degradation phenomena was developed based on existing assessments, new analyses, and staff experience. For each potential degradation process or issue, staff assessed the current level of knowledge, with particular emphasis on knowledge specifically related to performance of the dry storage SSC. NRC staff with experience in regulatory reviews of dry storage and transportation evaluated each of the SSC degradation mechanisms to determine how it could affect the ability of the SSC to meet the safety regulations for storage and transportation. For the final assessment, the staff prioritized the areas for further technical investigation, using the following criteria: 1)regulatory significance for safety performance: and 2) the level of knowledge about the process or issue. In general, those areas with high safety significance and low level of knowledge ranked highest for further investigation. In addition, the staff identified several crosscutting areas that can aid in understanding conditions affecting several SSCs and degradation processes. These crosscutting areas address effects of residual moisture after drying, thermal modeling, and monitoring methods, and are also given high priority.