Seismic Matters

The Electric Power Research Institute, U.S. Dept. of Energy and U.S. Nuclear Regulatory Commission released a new seismic study yesterday geared to help 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 4-year effort among the participating organizations and replaces previous seismic source models used by industry and government since the late 1980s," according to an NRC news release.

The NRC asks U.S. nuclear power plants to re-evaluate 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 release states. "The new seismic model will be used by nuclear power plants in the central and eastern United States for these re-evaluations, in addition to being used for licensing of new nuclear facilities."

The project gathered and analyzed information such as historical earthquake and geological data from 1568 through 2008 and used "a rigorous, peer-reviewed assessment process," the release states. "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 earthquake-caused ground motions.

"Calculations with the new model are expected to result in a higher likelihood of a given ground motion compared to calculations done using previous models," the release states. "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."

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.

"We will expect U.S. nuclear power plant owners to apply the model to their facilities to develop a new site-specific seismic risk analysis," NRC Public Affairs Officer Neil Sheehan said via email yesterday.

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