Input criterion for seismic analysis of nuclear power plants

This paper presents the results of a study made to assess the conservatism of applying the USNRC R.G. 1.60 spectrum at the foundation elevation in the free field. Two types of soil sites are investigated: (i) stiff soil site and (ii) deep cohesionless soil site. Several appropriate earthquake motions are selected such that the locations at which they were recorded are representative of the types of soil sites used in this study. The acceleration time histories of the recorded earthquake motions, scaled to the same peak acceleration (Asub(max) = 0.1 g), are applied at the surface and the resulting motions are obtained at various elevations in the free field. For each case, the soil properties are varied within a practical range (+- 50%). The resulting motions at various elevations are compared with the results obtained at the same elevations using the USNRC R.G. 1.60 spectrum for maximum ground acceleration equal to 0.1 g and applied at the foundation elevation. (orig.)