United States Nuclear Regulatory Commission - Protecting People and the Environment

Tsunami Hazard Assessment at Nuclear Power Plant Sites in the United States of America - Final Report (NUREG/CR-6966)

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Publication Information

Manuscript Completed: March 2009
Date Published: March 2009

Prepared by:
R. Prasad

Pacific Northwest National Laboratory
P.O. Box 999
Richland, WA 99352

E. Cunningham, NRC Project Manager
G. Bagchi, NRC Technical Monitor

Prepared for:
Office of New Reactors
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

NRC Job Code J3301

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Abstract

We describe the tsunami phenomenon with the focus on its relevance for hazard assessment at nuclear power plant sites. Chapter 1 includes an overview of tsunamis and mechanisms that generate tsunamis. Three tsunamigenic mechanisms—earthquakes, landslides, and volcanoes—are considered relevant for hazard assessment at nuclear power plant sites. We summarize historical tsunami occurrences, including descriptions of source mechanisms and damages caused by these events. Historical landslides and potential landslide areas in earth’s oceans are described. We describe the hierarchical-review approach to tsunami-hazard assessment at nuclear power plant sites in Chapter 2. The hierarchical-review approach consists of a series of stepwise, progressively more-refined analyses to evaluate the hazard resulting from a phenomena at a nuclear power plant site. We recommend that the hierarchicalreview approach employ a screening analysis to determine if a site is subject to tsunami hazard based on the presence of a tsunamigenic source and the location and elevation of the site. The screening analysis is expected to ensure that analysis and review resources are not wasted at sites with little potential of exposure to tsunamis. Chapter 3 describes the effects tsunami waves may have at a nuclear power plant site. These effects result in hazards that may directly affect the safety of a plant’s structures, systems, and components. Structures, systems, and components important to the safety of a plant should be adequately designed and, if required, protected from these hazards. Chapter 4 describes data required for a detailed tsunami-hazard assessment and sources of these data. We recommend using existing resources and previously completed tsunami-hazard assessments, if available and appropriate. Detailed tsunamihazard assessment at a nuclear power plant site should be based on the probable maximum tsunami. Chapter 5 defines the probable maximum tsunami, its determination at a site, and subsequent hazard assessment. We point out that a tsunamigenic source that produces probable maximum tsunami hazards at a site may not be determined a priori. It may be necessary to evaluate several candidate sources and the tsunamis generated from them under the most favorable tsunamigenic source and ambient conditions. The set of hazards obtained from all such scenario tsunamis should be considered to determine design bases of the plant structures, systems, and components. Chapter 6 describes international practices by Japan and the International Atomic Energy Agency, which are reviewed for completeness. The appendix provides a stepwise guide to site-independent analyses for tsunami-hazard assessment.

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