Seismic Hazard Evaluations for U.S. Nuclear Power Plants: Near-Term Task Force Recommendation 2.1 Results (NUREG/KM-0017)

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Publication Information

Manuscript Completed: June 2021
Date Published: December 2021

Prepared by:
Cliff Munson
Jon Ake
John Stamatakos
Miriam Juckett

Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

This document represents the current best knowledge and practices for characterizing the site-specific seismic hazards for each nuclear power plant (NPP) in the United States. The U.S. Nuclear Regulatory Commission (NRC) staff will use the hazard characterizations provided in this NUREG/KM as a benchmark to evaluate new data, models, and methods consistent with the staff’s process for ongoing assessment of natural hazard information provided in Staff Requirements Memorandum (SRM)-SECY-16-0144, "Staff Requirements—SECY-16-0144—Proposed Resolution of Remaining Tier 2 and 3 Recommendations Resulting from the Fukushima Dai-ichi Accident," dated May 3, 2017 (NRC, 2017). This document builds on the hazard assessments performed by the U.S. NPP licensees in response to the letter issued by the NRC under Title 10 of the Code of Federal Regulations (10 CFR) 50.54(f) [50.54(f) letter] and associated information requests (NRC, 2012) following the March 11, 2011, Great East Japan Earthquake and tsunami and resulting accident at the Fukushima Dai-ichi NPP.

The seismic hazard evaluations performed by U.S. NPP licensees used Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 seismic source and ground motion studies to develop probabilistic seismic hazard curves and ground motion response spectra for comparison with the plant design Safe Shutdown Earthquake Ground Motion (SSE). These SSHAC Level 3 studies incorporated the latest data, models, and methods that have been developed over the past 30 to 40 years and also systematically incorporated parametric and modeling uncertainty. As described in the 50.54(f) letter and Electric Power Research Institute (EPRI) Report 1025287, "Seismic Evaluation Guidance: Screening, Prioritization, and Implementation Details (SPID) for the Resolution of Fukushima NTTF Recommendation 2.1: Seismic," dated November 27, 2012 (EPRI, 2012), the ground motion response spectra (GMRS) developed by each of the licensees was compared to the plant SSE to determine (screen) which plants needed to perform new seismic risk evaluations. Section 1 of this NUREG/KM presents the ADAMS accession numbers for the NRC staff assessments of the Seismic Hazard and Screening Reports (SHSRs) for all operating U.S. NPPs and holders of construction permits in active or deferred status. Although the individual plant screening assessments are complete for the relevant NPP sites, the NRC staff was able to gather additional geologic data subsequent to its reviews of the licensees’ 50.54(f) SHSRs. The NRC staff used this additional information to refine and augment its analyses and provide a more representative characterization of the hazard for many of the NPP sites. However, it is important to note that the results contained within this report did not invalidate or change the conclusions documented in the NRC’s staff assessment for each NPP or the subsequent screening determinations made by the NRC staff.

In summary, this NUREG/KM presents a seismic hazard characterization for each U.S. NPP and compares the licensee’s hazard characterization and the NRC staff’s confirmatory analyses. This document also provides a comprehensive description of the probabilistic methods used by the U.S. NPP licensees and the NRC staff and summarizes spectral shapes and amplification functions for each NPP site.