ML24292A139
| ML24292A139 | |
| Person / Time | |
|---|---|
| Issue date: | 10/21/2024 |
| From: | Clifford Munson, Jacqueline Thompson Office of Nuclear Regulatory Research |
| To: | |
| Thomas Weaver 301-415-2383 | |
| Shared Package | |
| ML24292A135 | List: |
| References | |
| Download: ML24292A139 (1) | |
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Applying a Graded Approach and Adapting Guidance on Site Characterization of External Hazards for Advanced Reactor and Microreactor Applications Jenise Thompson and Clifford Munson, U.S. Nuclear Regulatory Commission In the last several years, the U.S. Nuclear Regulatory Commission has seen a shift away from light-water cooled reactor technologies to new designs that feature alternate cooling methods, enhanced safety characteristics, and smaller site footprints. Despite these advances in reactor technology, most of the current regulatory requirements and guidance were developed based on large light-water reactors and involve extensive site characterizations and investigations of the actual physical, environmental, and demographic features of a proposed site. As the NRC explores new ways to enhance the review process for siting emerging reactor designs, one exciting idea is to develop and apply a graded approach to site characterization. This approach could revolutionize how we evaluate external hazards at these sites, allowing for more flexible and tailored assessments that align with the unique features of each reactor design.
The graded approach to site characterization under development for advanced and microreactor designs is based on a screening analysis to determine the external hazards the design may be sensitive to and the bounding site parameters. Using this approach the applicant would determine the amount of margin between the site parameter value for the selected reactor design and the actual site characteristic value at the proposed deployment site, and between the doses calculated for the postulated design basis accidents at the boundary of the exclusion area and the 25 rem dose reference value in 10 CFR 50.34. This approach would allow an applicant to engage with the NRC to decide, for each hazard, which readily available information can be used to determine if further analysis is needed. The NRC staff also recognizes that because of the variation in external hazard demands and potential effects on a site, the graded approach may be applied differently for individual hazards. Depending on the results the NRC staff is considering whether a minimal level of site characterization could be used for all site characteristics if a low hazard site is selected. Conversely, if a site is selected with a high hazard related to a particular site characteristic, then there is the potential that the applicant will need to perform a traditional level of site characterization for that characteristic and a reduced or minimal level of site characterization for the other site characteristics.
The NRC staff is developing a draft white paper to describe this graded approach for microreactor applicants and plans for further stakeholder engagement in the coming months.
The NRC staff is also determining how to modify or adapt existing hazard analysis approaches for emerging reactor technologies. For example, Appendix K to DG-1290, the proposed Revision 3 to Regulatory Guide 1.59, provides specific considerations for how to adapt and apply the guidance on performing a flood hazard analysis to sites deploying an advanced reactor or small modular reactor design. For seismic hazard characterization, a four-level graded approach is provided in NUREG-2213. In addition, ANS 2.27, ANS 2.29, and ASCE 43-19 also provide guidance for graded approaches to seismic hazard characterization and design.