Seismic Source Characterization in Siting New Nuclear Power Plants in the Central and Eastern United States

摘要

The U.S. Nuclear Regulatory Commission (NRC) is currently reviewing several new reactor applications and is expected to receive more applications in the near future. Most of the proposed new reactor sites are located in the central and eastern United States (CEUS). In contrast to the western United States (WUS), the CEUS is less active in earthquake activity and can be considered as a low to moderate seismic area. Lack of surface expression of active faults and strong seismic recordings in the CEUS make seismic siting more difficult. Probabilistic seismic hazard analysis (PSHA) provides a tool to estimate seismic hazard for the CEUS because it is capable of incorporating uncertainties. The NRC endorsed the PSHA method and some PSHA models in Regulatory Guide 1.165, "Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion," issued March 1997. A popular practice for new applications is to use one of the recommended PSHA seismic source models as a starting point and update those source areas where new paleoseismic evidence have emerged since the models were published. However, most applications usually do not update other areas where there is no new paleoseismic evidence. The challenges are then that (1) these source models are almost 20 years old and, as indicated in Regulatory Guide 1.165, they need to be updated every 10 years, and (2) some other competing source models use very different theories and mechanisms to characterize the CEUS seismic sources in their PSHA methods. A subsequent question involves whether there is a need to completely update these source models to address the issues. Recently, the nuclear industry agreed to update the Electric Power Research Institute seismic source model published about 20 years ago and has a 2-year plan to reassess seismic sources in the CEUS. This paper presents some basic information about the seismic background in the CEUS and some key differences among the existing CEUS PSHA models for the discussion. In addition, the paper discusses the industry's plan to update the EPRI source model and potential challenges for the new update.