Geology in the Siting of Nuclear Power Plants
During the “great decade” of siting and construction of nuclear power plants that ended in 1975, the nuclear industry mustered the largest geologic task force in this country’s history, resulting in rapid advances in geologic technologies. Many of the advances are discussed in this volume, a major contribution to engineering geology. Subjects treated are the regulatory, siting, and licensing processes; seismicity of the central and western U.S., with a consumer’s guide to instrumental methods for determination of hypocenters; and techniques, such as remote-sensing, microfacies analysis, dating techniques in faults, trenching as an exploratory method, borehole geophysics, and ground-water studies. Includes a useful glossary.
The scope and detail of geologic studies made for a nuclear power plant site far exceed those made for any other type of engineering structure. The regional and local physiography, geomorphology, geologic history, lithology, stratigraphy, and structural geology must be studied through (1) reviewing the literature, (2) discussions with local, academic, State and Federal geologists, geophysicists, and seismologists, and (3) original geologic mapping, geophysical studies, and subsurface investigations. Reviews of previous studies in the region are an important part of the evaluation of any site; they help to identify, and form the basis for, additional detailed studies of particular geologic conditions and features which may be significant to that site.
All historical earthquakes that could have been felt at a proposed site should be identified. All historical earthquakes of modified Mercalli (MM) intensity greater than IV or magnitude greater than 3 which have been reported within 200 mi (320 km) of a site are listed and shown on epicenter maps that also show significant tectonic structures within 200 mi of the site. The maximum potential earthquake for the site is evaluated from a consideration of the regional and local geologic setting and the historical seismicity. The maximum vibratory ground motion that safety-related plant structures and equipment are designed to withstand is defined on the basis of an evaluation of the maximum potential earthquake and the assumed location of the earthquake that will produce the maximum vibratory ground motion.
Geologic, seismic, and man-made hazards significant to the site are identified and evaluated. The soils and rock underlying a site are investigated to determine their characteristics and behavior under static and dynamic loads. Safety Analysis Reports (SARs) for the site are prepared. They document the studies which were made by the applicant; they also document that pertinent reports and studies by others were considered. The SARs provide the basis for the conclusions as to the geologic suitability of the site and the basis for the parameters selected for engineering design.