Design Spectra for Nuclear Power Plants

A realistic determination of the design level of vibratory ground motion for nuclear power plants can be obtained by direct analysis of response spectra of existing accelerograms recorded under conditions representative of the Safe Shutdown Earthquake (SSE). The accelerograms recorded under conditions representative of the SSE are identified on the basis of the geologic and seismologic characteristics of the SSE (magnitude, distance, dimensions of fault break, source mechanism, travel path, and regional and local geology). In order to obtain response spectra at the level representative of the SSE, the representative accelerograms and their response spectra are linearly scaled for magnitude and distance using existing attenuation relations. When the response spectra scaled to a level representative of the SSE have been calculated and plotted, design spectra with the characteristics recommended in U.S. NRC Regulatory Guide 1.60 are conservatively fitted to them.