ML23298A134
| ML23298A134 | |
| Person / Time | |
|---|---|
| Issue date: | 10/27/2023 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| DG-4034, RG-4.007, Rev 4 | |
| Download: ML23298A134 (16) | |
Text
October 27, 2023 1
DG-4034 (RG 4.7, Revision 4)
Appendix A Alternative Approaches to Address Population-Related Siting Considerations
Agenda 11:00AM Introductions and Opening Remarks NRC 11:10AM Overview of DG Appendix A NRC 11:20AM Questions & Answers Session ALL 11:50AM Next Steps NRC 12:00PM Closing Remarks NRC 2
3 Background
- SECY-20-0045, Population Related Siting Considerations for Advanced Reactors
- ADAMS Accession No. ML19262H055
- SRM-SECY-20-0045 dated July 13, 2022
- ADAMS Accession No. ML22194A885 The Commission has approved the staffs recommended Option 3, to revise the guidance in Regulatory Guide 4.7, General Site Suitability Criteria for Nuclear Power Stations, related to Title 10 of the Code of Federal Regulations Part 100, Reactor Site Criteria, Section 100.21(h). That provision states that reactor sites should be located away from very densely populated centers and that areas of low population density are generally preferred. The revised guidance will provide technology-inclusive, risk-informed, and performance-based criteria to assess population-related issues in siting advanced reactors. With respect to the traditional dose assessment approach, the staff should provide appropriate guidance on assessing defense-in-depth adequacy and establishing hypothetical major accidents to evaluate.
4 10 CFR 100.21(a) 10 CFR 50.34/52.79 Exclusion Area boundary (EAB) 25 rem - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 10 CFR 100.21(a) 10 CFR 50.34/52.79 Low Population Zone (LPZ) 25 rem - duration 10 CFR 100.21(b)
Population Center Distance (PCD) 11/3 dLPZ Background - Requirements/Guidance 10 CFR 100.21(h)
Located away from populated centers and low population density preferred Regulatory Guide 4.7 (Population Density)
Primary Focus
5
- Publication
- Federal Register 88 FR 71777; 10/18/202
- Regulations.gov Docket NRC-2023-0153
- Comments Due: November 17, 2023 Acceptable optional alternative to using 20-mile distance provided for:
- Non-light water reactors under licensing modernization project (LMP) methodology
- Light water reactors under traditional (containment) methodology
- Non-light water reactors under traditional (non-LMP) methodology DG-4034; Appendix A
6 Source term for siting analysis Additional Information provided in:
Regulatory Guide 1.183 Regulatory Guide 1.233 Footnote (6) - 10 CFR 50.34 The fission product release assumed for this evaluation should be based upon a major accident, hypothesized for purposes of site analysis or postulated from considerations of possible accidental events. Such accidents have generally been assumed to result in substantial meltdown of the core with subsequent release into the containment of appreciable quantities of fission products.
Final Rule; Reactor Site Criteria Including Seismic and Earthquake Engineering Criteria for Nuclear Power Plants (61 FR 65157, December 11, 1996)
Limitation of population density beyond the exclusion area has the following benefits:
(a)It facilitates emergency preparedness and planning; and (b)It reduces potential doses to large numbers of people and reduces property damage in the event of severe accidents.
10 CFR 100.21(h) 10 CFR 100.21(a) 10 CFR 50.34/52.79
7 Analyses related to estimated doses at EAB/LPZ (50.34)
- Design Basis Accidents Analyses related to optional alternative to existing population density guidance (500 persons per square mile (ppsm) out to 20 miles)
- Design Basis Events (DBEs) and Beyond Design Basis Events (BDBEs)*
- Outputs used to determine distance at which an event results in 1 rem TEDE over 30 days
- Mechanistic Source Term for various event sequences (release categories)
- Risk metrics under LMP based on mean frequency and mean consequence of event sequences
- Decision-making informed by other factors such as uncertainties and assessment of potential cliff-edge effects Note ongoing discussions related to low frequency, high consequence seismic events Non-LWR under LMP
8 Analyses related to estimated doses at EAB/LPZ
- Regulatory Guide 1.183*
Analyses related to optional alternative to existing population density guidance (500 ppsm out to 20 miles)
- Population density analysis outputs used to determine distance at which an event results in 1 rem TEDE over 30 days
- Regulatory Guide 1.183 source term can be used
- Accounting for potential containment performance under severe accident conditions
- DG-4034 discusses possible analyses ranging from bounding assumptions and simple modeling to a high level of realism and detail (tradeoffs between analyses conservatisms and flexibility in plant design or needed programmatic controls)
Note recent issuance of Revision 1 to RG 1.183 LWR under traditional approach
9 Analyses related to estimated doses at EAB/LPZ
- Regulatory Guide 1.183 like approach Analyses related to optional alternative to existing population density guidance (500 ppsm out to 20 miles)
- Population density analysis outputs used to determine distance at which an event results in 1 rem TEDE over 30 days
- Regulatory Guide 1.183 like source term can be used o Range of conservatism vs realism (with related analyses & testing)
- Accounting for potential containment performance under severe accident conditions
- DG-4034 discusses possible analyses ranging from bounding assumptions and simple modeling to a high level of realism and detail (tradeoffs between analyses conservatisms and flexibility in plant design or needed programmatic controls)
Non-LWR under traditional approach
10 Questions and Discussion
Next Steps
- Public comment period closes 17 Nov 2023
- Resolve public comments
- Issue Final RG 4.7 Rev. 4 February 2024 11
12 Background Slides
13 SECY-20-0045 Option 3 Considerations
14 Option 3 - Example Cases
15 Option 3 - Example Cases
16 Option 3 - Example Cases