ML24355A115
| ML24355A115 | |
| Person / Time | |
|---|---|
| Issue date: | 10/30/2024 |
| From: | Miriam Juckett, Clifford Munson, Payne R, Rodriguez-Marek A, Stamatakos J, Scott Stovall, Ulmer K, Thomas Weaver NRC/RES/DE, Pacific Northwest National Laboratory, Southwest Research Institute |
| To: | |
| Thomas Weaver 301-415-2383 | |
| Shared Package | |
| ML24355A102 | List: |
| References | |
| Download: ML24355A115 (26) | |
Text
SSHAC Level 1 Demonstration Project DOE/NRC Natural Phenomena Hazards Meeting October 30, 2024 John Stamatakos and Kristin Ulmer (SwRI)
Cliff Munson, Ryan Payne, Scott Stovall, and Thomas Weaver (NRC)
Adrian Rodriguez-Marek (VT), Miriam Juckett (PNNL) 1
Objective The objective of this study is to illustrate how a Senior Seismic Hazard Analysis Committee (SSHAC) Level 1 study can be used to develop the seismic hazard for some advanced nuclear power plant designs.
Follow Guidance in NUREG-2213.
2
Five Essential Elements of SSHAC 3
1.
Clearly Defined Roles for all participants.
2.
Objective Evaluation of all available data, models, and methods that could be relevant to the characterization of the hazard at the site.
3.
Integration of the outcome of the evaluation process into models that reflect both the best estimate of each element of the hazard input with the current state of knowledge and the associated uncertainty.
4.
Documentation of the study with sufficient detail to allow reproduction of the hazard analyses.
5.
Independent Participatory Peer Review to confirm that the evaluation considered relevant data, models, and methods, and that the evaluation was conducted objectively and without bias.
Goals Demonstrate how a SSHAC L1 can be completed in 6-9 months with sufficient evaluation and integration of available data, models, and methods to capture the Center, Body, and Range of Technically Defensible Interpretations (CBR of TDI).
Evaluate contributions to the seismic hazard at annual frequencies of exceedance (AFE) consistent with seismic design/risk profile of advanced reactors (10-3/yr to 10-4/yr, rather than current range of 10-4/yr to 10-5/yr for large light water reactors).
Rely on as much existing information as practicable.
Identify what simplifications can be made in the source and ground motion models (i.e., trimmed logic tree branches) to successfully complete a SSHAC L1 study.
4
5 SSHAC L1 Structure
Team Structure PPRP
- Gabriel Toro 6
TI Team
- John Stamatakos (TI Lead)
- Cliff Munson
- Adrian Rodriguez-Marek
- Ryan Payne
- Kristin Ulmer Project Manager
Schedule and Milestones Schedule
- Initiated Project February 2024
- Weekly TI Team Calls
- One PPRP Briefing (one more left)
- Final Reports completed by the end of 2024 Milestones
- Site Selection Report
- Draft and Final PSHA Report
- SSHAC L1 Recommendations Report 7
Pick a Representative Site Characteristics - reasonably complex site to explore ways to simplify approaches while maintaining reasonable CBR of TDI (with a focus on the C)
- Both fault and source zones
- Soil above bedrock
- Distant and nearby sources (explore a range of spectral accelerations)
- Representative of the types of sites applicants will likely seek Focus on items that impact the hazard at higher AFEs, consistent with seismic design category (SDC) - SDC-4, SDC-3, and SDC-2.
8
Basis for Site Selection Report transmitted to NRC on June 6, 2024
Site Selection Criteria
- The site should be in the western United States (WUS). NUREG-2115 (EPRI/DOE/NRC, 2015) already provides a seismic source model for all sites east of longitude 105°W.
- The site should be representative of the types of sites applicants will likely seek for advanced reactors.
- The site should be reasonably complex in terms of the seismicity and local and regional geology to allow the TI Team to explore ways to simplify evaluation and integration approaches.
Site Selection Criteria (Contd.)
- The site should have sufficient data to test sensitivities that support the development of guidance for streamlining the evaluation and integration process while ensuring that the SSHAC Level 1 study captures the center, body, and range of technically defensible interpretations.
- The site should include seismicity from both fault sources and source zones and both local and distant source zones, especially to explore the full range of spectral accelerations in the site response spectra.
- The site should include soil and other surficial sedimentary deposits (e.g.,
fluvial, floodplain, and lacustrine deposits, alluvium, and colluvium) above bedrock, ensuring that the PSHA includes a relatively complex site VS profile and site response analysis.
Skull Valley Assets
- Available site data (e.g., VS)
- Both fault and areal sources; both local and distant fault sources
- Moderate background seismicity rates
- Previously performed PSHA (Geomatrix, 1999).
- Supporting data from the USGS and the Utah Earthquake Working groups
Available Site Data Industry gravity data 2D Seismic reflection profiles (p and s)
Geologic cross-sections Borings CPT Downhole Vs profiles (30 and 106 ft)
Laboratory tests (void ratios, direct shear tests, Atterberg limits)
ML010320580: Safety Analysis Report, June 1997 ML061590385: Final Safety Analysis Report, V1 2006 ML061590426: Final Safety Analysis Report, V2, 2006 ML010360150: Fault Evaluation Study and Seismic Hazard Assessment, February 1999 ML010090332: Plate 6 Quaternary Faults Fault evaluation study and seismic hazard assessment study Final Environmental Impact Statement - NUREG-1714, 2001
Seismic Source Model
Faults
USGS Quaternary Faults USGS Quaternary Fault and Fold Database of the United States Interactive Map NSHM Fault Sections NSHM23_EQGeoDB_v3
Swan, F.H., Hanson, K.L., Angell, M.M.
(2005). Paleoseismic Investigations of the Stansbury and Mid-Valley Faults, Skull Valley, Utah, Proceedings Volume Basin and Range Province Seismic Hazard Summit II, Edited by William R. Lund
Ground Motion Model Independently developed a generic ground motion model for the western U.S. (GWUS Model) - presented earlier today by Scott Stovall.
Analysis Approach
- Equivalent-linear (EQL)
- Kappa-corrected EQL Site Kappa Models
- Q-Vs models (Campbell 2009)
- Kappa from Vs30 and Z2.5 (Xu et al. 2020)
Modulus Reduction and Damping Curves
- Incorporated limited data from site-specific testing
- Selected from evaluation of published models (e.g., EPRI, Darendelli and Stokoe, Peninsular, and Vucetic and Dobry)
Site Response Analysis
Shallow Profile (< 38 m): Downhole, seismic CPT from geotechnical investigations Deep Profile (> 38 m): Model for nearby Salt Lake Valley (Zeng et al. 2022)
Shear Wave Velocity (Vs) Data
Performed sensitivity study to determine the relative contributions of each of the nodes from the SSM and GMM logic trees
Purpose:
determine if the SSM and GMM logic trees could be simplified to save computational time
- Focus on Stansbury fault only (expected to be significant contributor)
- Excluded site response logic tree (seven resampled branches, no need to further simplify)
Used results to trim the complete logic tree to get a reduced logic tree Compared hazard curves from complete logic tree combinations (36,450 )
vs. reduced logic tree combinations(2,025)
Determining Hazard Significance to Simplify Calculations
23 Less influential (Seismogenic Thickness)
More influential (Fault Slip Rates)
24 Complete set Reduced set
Conclusions Developed a draft PSHA for Skull Valley following SSAHC Level 1 process (currently undergoing PPRP review)
Developed a companion recommendations report to support the SSHAC L1 Study
- Generic Western U.S. ground motion model (GWUS)
- Full integration of the hazard analysis within the evaluation and integration process to keep the TI Team focused on only those model components that contribute to hazard
- Developed logic tree simplifications that maintained CBR of TDI and that reduced the complexity and computation needs of the hazard calculations 25
Questions 26