January 31, 2012 — The Electric Power Research Institute, the U.S. Department of Energy and the U.S. Nuclear Regulatory Commission released a new seismic study that will help U.S. nuclear facilities in the central and eastern U.S. reassess seismic hazards.
The Central and Eastern United States Seismic Source Characterization for Nuclear Facilities model and report is the culmination of a four-year effort among the participating organizations and replaces previous seismic source models used by industry and government since the late 1980s.
The NRC is requesting U.S. nuclear power plants to reevaluate seismic hazards using this information as well as other guidance. This work is part of the agency's implementation of lessons learned from events at the Fukushima Daiichi nuclear power plant following the March 2011 earthquake and tsunami in Japan.
The new seismic model will be used by nuclear power plants in the central and eastern U.S. for these reevaluations, in addition to being used for licensing of new nuclear facilities.
The project gathered and analyzed an expanded data set — including historical earthquake and geological data for the entire study region from 1568 through 2008 — using a peer-reviewed assessment process. National and international experts from industry, government, academia, and various research organizations were engaged to develop the model.
The model can be used to calculate the likelihood of various levels of earthquake-caused ground motions. Reflecting the additional data and revised analytical approaches, calculations with the new model may result in a higher likelihood of a given ground motion compared to calculations using previous models.
These calculations, however, are not equivalent to a nuclear power plant's overall risk. Plant operators must combine the information from the new model with a plant's design and safety features to determine site-specific risks.
As part of the project, the new seismic model was compared to previous models by calculating seismic hazards at seven test sites. The sample calculations indicate that the largest predicted ground motions could occur in the vicinity of repeated large magnitude earthquake sources, such as New Madrid, Mo., and Charleston, S.C.