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Monday, April 4, 2011

Nuclear Power Plant Sites: Maps of Seismic Hazards and Population Centers

Anthony Andrews
Specialist in Energy and Defense Policy

Currently, 104 commercial nuclear power plants operate on 64 sites in the 48 contiguous United States. 1 Sixty-nine of the 104 are pressurized water reactors (PWR) and the 35 remaining are boiling water reactors (BWR). The PWR plants are based on Babcock & Wilcox, Combustion Engineering, and Westinghouse designs. The BWR plants are based on a series of General Electric designs. The Nuclear Regulatory Commission (NRC) has received 28 Combined License (COL) applications for new reactors based on advanced reactor designs (Table 2). Three COL applications will involve new sites.

CRS determined the coordinates of plant sites using web-based applications and overlaid the sites on base maps of: 
  1. Quaternary faults, 
  2. Seismic hazards in terms of percent gravitational acceleration, 
  3. Levels of horizontal ground shaking (gravitational acceleration) that have a 2-in- 100 (2%) probability of being exceeded in a 50-year period, and 
  4. Metropolitan populations 

To map the proximity of plant sites to faults (Figure 1), CRS referred to the USGS Quaternary Fault and Fold Database of the United States.
2 This database contains information on faults and associated folds in the United States that are believed to be sources of greater than magnitude 6 (M>6) earthquakes during the Quaternary (the past 1,600,000 years). It is important to note that this map is not a prediction of an earthquake event.

To map the proximity of plant sites to seismic hazards (Figure 2), CRS referred to the USGS Seismic Hazard Map for the United States.
3 This map displays quantitative information about seismic ground motion hazards as horizontal ground acceleration (in terms of gravitational acceleration) of a particle at ground level moving horizontally during an earthquake. It is important to note that this map is not a prediction of an earthquake event.

To map the proximity of plant sites to geographic areas with levels of horizontal shaking having a 2% probability of being exceeded in a 50-year period (Figure 3), CRS referred to the 2008 United States National Seismic Hazard Maps.
4 The U.S. Geological Survey (USGS) National Seismic Hazard Maps incorporate the latest findings on earthquake ground shaking, faults, seismicity, and geodesy to display earthquake ground motions for various probability levels across the United States. The resulting maps are derived from seismic hazard curves calculated on a grid of sites across the United States that describe the frequency of exceeding a set of ground motions. The Seismic Hazard maps are the basis for seismic design provisions of building codes to allow buildings, highways, and critical infrastructure to withstand earthquake shaking without collapse.5 The NRC requires that every nuclear plant be designed for site-specific ground motions that are appropriate for their site locations. In addition, the NRC has specified a minimum ground motion level to which nuclear plants must be designed. For further information about nuclear power plant siting criteria, refer to 10 Code of Federal Regulation, Appendix A to Part 100— Seismic and Geologic Sitting Criteria for Nuclear Power Plants. It is important to note that this map is not a prediction of an earthquake event.

For further information about earthquake hazards, refer to CRS Report RL33861, Earthquakes: Risk, Detection, Warning, and Research, by Peter Folger.

Date of Report: March 29, 2011
Number of Pages: 10
Order Number: R41729
Price: $29.95

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