Investigation of techniques for the development of seismic design basis using the probabilistic seismic hazard analysis

The Nuclear Regulatory Commission asked Lawrence Livermore National Laboratory to form a group of experts to assist them in revising the seismic and geologic siting criteria for nuclear power plants, Appendix A to 10 CFR Part 100. This document describes a deterministic approach for determining a Safe Shutdown Earthquake (SSE) Ground Motion for a nuclear power plant site. One disadvantage of this approach is the difficulty of integrating differences of opinions and differing interpretations into seismic hazard characterization. In answer to this, probabilistic seismic hazard assessment methodologies incorporate differences of opinion and interpretations among earth science experts. For this reason, probabilistic hazard methods were selected for determining SSEs for the revised regulation, 10 CFR Part 100.23. However, because these methodologies provide a composite analysis of all possible earthquakes that may occur, they do not provide the familiar link between seismic design loading requirements and engineering design practice. Therefore, approaches used to characterize seismic events (magnitude and distance) which best represent the ground motion level determined with the probabilistic hazard analysis were investigated. This report summarizes investigations conducted at 69 nuclear reactor sites in the central and eastern U.S. for determining SSEs using probabilistic analyses. Alternative techniques are presented along with justification for key choices. 16 refs., 32 figs., 60 tabs