ML22312A445
| ML22312A445 | |
| Person / Time | |
|---|---|
| Issue date: | 11/08/2022 |
| From: | Bauer L NRC/NRR/DEX/EXHB |
| To: | |
| References | |
| Download: ML22312A445 (1) | |
Text
Seismic Hazard Updates for Operating Nuclear Power Plants in the Central and Eastern U.S.
Laurel Bauer Office of Nuclear Reactor Regulation November 29, 2022
2 NRC Team:
Geologists: Laurel Bauer and Jenise Thompson Seismologists: Cliff Munson, Scott Stovall, and Thomas Weaver Risk Analysts: Steven Alferink, Sunwoo Park, De Wu
3
Background:
Seismic Hazard Reevaluations SECY-11-0093 Near-Term Report and Recommendations for Agency Actions Following the Events in Japan, July 12, 2011 (ML11186A959)
NTTF Recommendation 2.1 initiated the seismic hazard reevaluation Staff completed these reviews in 2019 NUREG/KM-017, Seismic Hazards Evaluations for U.S.
Nuclear Power Plants: Near Term Task Force Recommendation 2.1 Results, December 2021 (ML21344A126)
4 Results From NTTF Activities NTTF 2.1 seismic hazard reevaluation activities demonstrated that the nuclear power plants continue to operate safely NRC and the nuclear power plant licensees derived important insights related to seismic risk Walkdowns Expedited Seismic Evaluation Process (ESEP)
High Frequency Evaluation Seismic Probabilistic Risk Assessments (SPRAs)
5 Results from NTTF Activities Process for the Ongoing Assessment of Natural Hazards Information (POAHNI)
NTTF 2.2 advised rulemaking requiring that nuclear power plant licensees confirm seismic and flooding hazards every 10 years SECY-16-0144, Proposed Resolution of Remaining Tier 2 and 3 Recommendations Resulting from the Fukushima Dai-ichi Accident, dated December 26, 2016 (ML16286A552)
Office of Nuclear Reactor Regulations Office Instruction LIC 208, Process for the Ongoing Assessment of Natural Hazards Information, issued November 2019 (ML19210C288)
6 Meeting
Purpose:
Describe approach for updating seismic hazard curves for CEUS NPP sites using the NRC process for ongoing assessment of natural hazards information (POANHI)
Update incorporates New seismic ground motion attenuation models: NGA-East Updated seismic site response methods used to better capture uncertainty Provide schedule for updated hazard curves and report
Seismic Hazard Characterization 7
8 Recent Seismic Hazard Updates: NGA-East GMM
NGA-East is a ground motion model (GMM) for the Central and Eastern United States Captures larger range of uncertainty than previously NRC endorsed model Developed jointly with industry, NRC, DOE, and USGS using SSHAC process
NGA-East GMM used for multiple critical facility siting evaluations
NGA-East GMM replaces older EPRI ground motion model for the Central and Eastern United States
Impact of NGA-East Model 9
10 Recent Seismic Hazard Updates: Site Response Analysis
CEUS NPP sites licensed in the 1970s and early 1980s have less detailed subsurface information on soil and rock properties below the plant foundation level
Updated site response analysis approach captures larger range of uncertainty for important modeling inputs
Add more site profiles to capture depth to basement rock layer
Add more models to capture nonlinear response of soil and rock to higher input ground motions
Use more relationships to capture local site attenuation parameter - kappa
Site response logic tree now has many more alternative branches and nodes
Impact of Site Response Updates 11 Two alternative basement rock horizons
Probabilistic Seismic Hazard Curves 12 Site New Madrid Charleston Charleston New Madrid
13 Example: GMRS comparison for NPP Site
Seismic Screening under POANHI 14 Step 1 Develop hazard curves and GMRS for CEUS NPP site Step 2 Do screening evaluation Step 3 Prepare hazard report and cover letter Step 4 Discuss results with NRC Senior Management Review Panel (SMRP)
Step 5 Contact Licensee to notify about issuance of hazard report or to discuss seismic risk evaluation
Screening Flow Chart 15 Hazard Screen for New GMRS Risk Screen Inform Licensee and issue report
Further Risk Analysis 16
- Utilize available plant-specific seismic risk insights; Examples:
- Dominant risk contributors
- Safety enhancements performed by licensee via permanent plant modifications
- If issues resolved, inform licensee and issue final letter and hazard report
- If issues remain, enter formal regulatory process
Hazard Report Information report that documents updated seismic hazard results Provides background, methodology, and bases for updated seismic hazard curves Hazard curves and site properties provided as figures and tables in the report 17
CEUS NPP Schedule 18 PLANT SITE Initial Screening Evaluation (CY)
Vogtle 4th Qtr 2022 Robinson 4th Qtr 2022 Watts Bar 1st Qtr 2023 Sequoyah 1st Qtr 2023 Browns Ferry 1st Qtr 2023 North Anna 1st Qtr 2023 Summer 2nd Qtr 2023 Peach Bottom 2nd Qtr 2023 D.C. Cook 2nd Qtr 2023 Dresden 2nd Qtr 2023 Oconee 3rd Qtr 2023 Beaver Valley 3rd Qtr 2023 Callaway 3rd Qtr 2023
CEUS: Central and Eastern United States
ESEB: Expedited Seismic Evaluation Process
GMM: Ground Motion Model
GMRS: Ground Motion Response Spectra
HCLPF: High Confidence of Low Probability of Failure
NGA East: Next Generation Attenuation for Central and Eastern North America
NPP: Nuclear Power Plant
NTTF: Near Term Task Force
POANHI: Process for the Ongoing Assessment of Natural Hazards Information
PSHA: Probabilistic Seismic Hazard Analysis
RLME: Repeated Large Magnitude Earthquake
SCDF: Seismic Core Damage Frequency
SMRP: Senior Management Review Panel
SPRA: Seismic Probabilistic Risk Assessment
SSE: Safe Shutdown Earthquake 19