ML21272A014
| ML21272A014 | |
| Person / Time | |
|---|---|
| Issue date: | 01/28/2020 |
| From: | Jon Ake, Miriam Juckett Office of Nuclear Regulatory Research, Southwest Research Institute |
| To: | |
| S. Stovall | |
| Shared Package | |
| ML21272A001 | List: |
| References | |
| Download: ML21272A014 (14) | |
Text
Introduction and Objectives Presentation Miriam Juckett, SwRI Jon Ake, NRC January 28, 2020 1
U.S. Nuclear Regulatory Commission SSHAC Level 2 Workshop:
Site Response
Outline Workshop Logistics Overview of SSHAC Motivation and Objective for this Project Direction and Scope
Workshop Logistics On-site logistics
- Emergency exits
- Restrooms
- WiFi
- Parking
- Snacks/Drinks/Coffee
- Lunches - order form
- Dinners - update and locations Workshop Materials Sign-in Sheet and Introductions
What is SSHAC?
Senior Seismic Hazard Analysis Committee (SSHAC)- a group established in the 1990s with the goal of investigating the reason(s) for differences in two major probabilistic seismic hazard analysis studies for the central and eastern U.S. conducted in the 1980s.
The SSHAC concluded the primary reason for the differences were procedural rather than technical.
In their report (NUREG-6372) the group made a number of suggestions for conducting future studies that would (hopefully) minimize the impact of procedural issues.
The guidance has been applied in a number of studies throughout the world.
Guidance subsequently expanded and updated in NUREG-2117 and 2213.
Goal of a SSHAC Process The fundamental goal of a SSHAC process is to properly carry out and completely document the activities of evaluation and integration, defined as:
Evaluation: The consideration of the complete set of data, models, and methods proposed by the larger technical community that are relevant to the hazard analysis.
Integration: Representing the center, body, and range of technically defensible interpretations [CBR of the TDI] in light of the evaluation process (i.e., informed by the assessment of existing data, models, and methods).
5 NUREG-2117/2213
Key SSHAC Concepts These five features are essential for all SSHAC hazard studies regardless of the SSHAC Level and distinguish SSHAC studies from non-SSHAC studies Clearly defined roles for all participants, including the responsibilities and attributes associated with each role.
Objective evaluation of all available data, models, and methods that could be relevant to the characterization of the hazard at the site.
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. This distribution is referred to as the Center, Body, and Range of Technically-Defensible Interpretations, or the CBR of the TDI.
Documentation of the study with sufficient detail to allow reproduction of the hazard analyses.
Independent participatory peer review is required to confirm that the evaluation did consider relevant data, models, and methods, and that the evaluation was conducted objectively and without bias. The peer review is conducted following a participatory or continual process throughout the entire project.
Key SSHAC Concepts Capturing the Center, Body and Range of Technically Defensible interpretations (the CBR of TDI)
SSHAC Level 2 Workflow Note: replace SSC and GMC with SRA
SSHAC Team Roles Role Participant (Organization)
Responsibilities Project Manager Miriam Juckett (CNWRA)
Provides overall coordination and responsibility for organizational and administrative aspects of the project. Is the liaison between the Sponsor and the project participants, as needed.
Technical Integration Team Lead and Members Dr. Adrian Rodriguez-Marek (TI Lead; Independent Consultant)
Dr. Jon Ake (NRC)
Dr. Cliff Munson (NRC)
Dr. Ellen Rathje (Independent Consultant)
Responsible for developing the models and final recommendations for incorporation of site response.
Hazard Analysts and Database Managers Dr. Scott Stovall (NRC)
Dr. Thomas Weaver (NRC)
Responsible for establishing and managing necessary data sets and executing calculations and sensitivity studies and documenting the final results according to the inputs developed by the TI Team.
Sponsor Represented by NRC Contracting Officers Representative, Dr. Scott Stovall (NRC)
Funds the study and provides input as requested on the Project Plan; works with Project Manager to ensure that the purpose, process, and outcomes of the study will meet Sponsor goals.
Participatory Peer Review Panel (PPRP)
Dr. Dogan Seber (NRC)
Dr. John Stamatakos (CNWRA)
Dr. Jeff Kimball (Independent Consultant)
Responsible for technical and process reviews to ensure the SSHAC approach is implemented per regulatory guidance At the end of the study, if acceptable, documents approval in a closure letter.
Seismic Design/Analysis For Nuclear Plants 1
2 3
4
Motivation All recent PSHA studies for commercial nuclear facilities in the U.S. have included ground motion characterization (GMC) and seismic source characterization (SSC) studies carried out following the SSHAC framework and guidance (generally Level 3).
However, site response analyses (SRA) have typically been conducted as a discrete activity outside of the SSHAC framework.
Is it practical and effective to conduct the SRA following the SSHAC guidance as well and receive the enhanced regulatory assurance that comes with that process?
Given the enhanced focus on risk informed decision making, what are the best method(s) for incorporating uncertainties into the site-specific hazard calculations?
Current practice for PSHAs conducted for critical facilities often incorporates the concept of partially non-ergodic PSHA, incorporating a single-station sigma as the aleatory variability in the reference rock PSHA.
- Single-station sigma removes the site-to-site variability portion of the fully ergodic sigma necessitating the proper characterization of epistemic or knowledge-based uncertainties in the site term (e.g., in site response) in the final hazard calculations.
Objective and Caveat Objective: To evaluate how site response analysis results are integrated into the PSHA to properly account for the epistemic uncertainty and aleatory variability of relevant site response data, models, and methods.
- Focus on identifying epistemic uncertainty vs. aleatory variability, then quantify each in the site term (for each example site)
- Perform a Senior Seismic Hazard Analysis Committee (SSHAC) Level 2 study to investigate how site response inputs should be defined and quantified, and subsequently incorporated into PSHA computations.
Caveat: This project may utilize data from existing sites. However, the purpose of this study is not to re-evaluate the seismic hazard at a specific site, or outcomes of any prior assessments. The outcomes will be used to inform future site response analyses and provide information to the Sponsor (NRC) for potential changes or enhancements to regulatory guidance.
Site Selection Criteria Criterion WUS: Garner Valley Array CEUS:
Savannah River Site Suitable Site Properties for Nuclear Facility
Potential for Nonlinear Behavior
Abundant Site Characterization*
Local Ground Motion Recordings
X Realistic Reference Hazard Level X
Site characterization data must be publicly available or available in a time frame consistent with project schedule
Future Direction and Scope Project Direction: This is a research project.
- Attempt to satisfy objective, answer motivating questions. However-direction will evolve (answers lead to new questions, comments/insights from PPRP and workshop).
- As direction evolves, try to capture in Project Plan updates Scope: This is a research project. Project resources will ultimately constrain the scope.
In addition to workshop, TI Team will be conducting interactions (phone interviews) with other experts not present at the WS.