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
Background:
3 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)
Results From NTTF 4 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)
Results from NTTF 5 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
7 Seismic Hazard Characterization
Recent Seismic Hazard 8 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
9 Impact of NGA-East Model
Recent Seismic Hazard 10 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
11 Impact of Site Response Updates Two alternative basement rock horizons
Probabilistic Seismic 12 Hazard Curves New New Madrid Madrid Charleston Site Charleston
Example: GMRS comparison for NPP Site 13
Seismic Screening under 14 POANHI Step 1 Step 2 Step 3 Step 4 Step 5 Develop Do screening Prepare Discuss results Contact hazard curves evaluation hazard report with NRC Licensee to and GMRS and cover Senior notify about for CEUS NPP letter Management issuance of site Review Panel hazard report (SMRP) or to discuss seismic risk evaluation
Screening Flow Chart 15 Inform Licensee and issue report Hazard Risk Screen for Screen New GMRS
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 17 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
18 CEUS NPP Schedule 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
ACRONYMS 19 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