ML24355A104
| ML24355A104 | |
| Person / Time | |
|---|---|
| Issue date: | 10/30/2024 |
| From: | Clifford Munson, Jacqueline Thompson NRC/NRR/DEX |
| To: | |
| Thomas Weaver 301-415-2383 | |
| Shared Package | |
| ML24355A102 | List: |
| References | |
| Download: ML24355A104 (12) | |
Text
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 Office of Nuclear Reactor Regulation Division of Engineering and External Hazards October 30, 2024 1
Whats changing in nuclear?
- Reactor design characteristics
- Smaller footprint
- Lower radiological risk
- Modular designs
- Transportable designs
- Pre-fabricated reactor units deployed to multiple sites 2
Why a graded approach?
- Graded approach to site characterization
- Flexible and tailored assessments that align with the unique features of emerging reactor designs
- Focus on screening for external hazards to which the design may be sensitive and determining margin
- Leverage readily available information
- NUREG-2213 and different levels of SSHAC study 3
A Graded Approach for Microreactors 4
Considerations for a Graded Approach
- Hazard, site and design-specific considerations
- Degree of grading may not apply equally to all hazards
- Not all sites will consider the same hazards
- Not all designs are sensitive to the same hazards
- How to leverage existing site characterization information?
- How to adapt current hazards analysis approaches within a graded approach?
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Other Uses for a Graded Approach
- Expedited COL reviews
- Similar to microreactor approach with approved standard design
- Focus on hazards the design is sensitive to and that are present at the candidate site
- Brownfield site
- Focus on applicability of existing site characterization information 6
Using Existing Site Characterization Information
- Many site may have site characterization information available from nearby facilities
- NRC-licensed or others (i.e. brownfields or former coal sites)
- Determine which information is applicable for NRC licensing actions
- Vintage of information
- Methods used
- Regulatory applicability to meet current requirements 7
Current Hazard Analysis Approaches
- Seismic Hazards
- NUREG-2213 provides 4-level graded approach for performing SSHAC study
- Level 3 studies developed for each operating NPP site in the U.S.
- Level 2 Site Response Analysis study completed in 2019
- ANS 2.27, 2.29 and ASCE 43-19 provide guidance for graded approaches to seismic hazard characterization and design 8
Adapting Hazard Analysis Approaches
- Volcanic Hazards
- RG 4.26
- Flooding Hazards for SMRs and Advanced Reactors
- Proposed in Appendix K to DG-1290 9
- Flexible, stepwise approach with multiple off-ramps
- Leverage existing site characterization information
- Screen hazards and consider risk insights
- Evaluate SSC performance and mitigating actions in addition to or in place of detailed hazard analysis 10
DG-1290, Appendix K
- End the flood evaluation at the earliest possible point in the process.
- Focus on flood causing mechanisms of importance to the design
- Consider PRA or comparable analysis
- Iterate between evaluation of SSCs performance and mitigating actions and design reassessment to achieve satisfactory result.
Figure K-1, DG-1290, Rev. 1 11
Thank you!
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