Energy Department and NRC release new seismic study for nuclear plants in eastern U.S.

North Anna nuclear power station

The agencies in charge of regulating the safety of nuclear power plants in the U.S. released a new study of seismic activity in the eastern and central U.S. aimed at updating a 20-year-old seismic model.

The Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and the U.S. Nuclear Regulatory Commission (NRC) said on Jan. 31 that the new study will help U.S. nuclear facilities in central and eastern states reassess seismic hazards. It noted that the greatest risk of earthquakes in the east is probably around areas that have seen big temblors in the past, such as Charleston, SC.

The study comes months after one of the largest earthquakes in 100 years shook the eastern seaboard. In August, a 5.8 magnitude earthquake centered in central Virginia, forced the nearby North Anna nuclear power plant to shut down. A massive, killer earthquake and tsunami that devastated the nation of Japan last spring, resulting in a meltdown of three nuclear reactors at plant in Fukushima.

The North Anna plant in Virginia was built, like some others in the eastern U.S., to withstand a 6.1 magnitude quake.

On Jan. 31, the NRC said the new 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.

In releasing the study, the NRC said it was requesting U.S. nuclear power plants to re-evaluate seismic hazards using the information as well as other guidance. It said 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.

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, it said.

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 rigorous, peer-reviewed assessment process, said the agency. National and international experts from industry, government, academia, and various research organizations were engaged to develop the model, it added.

According to the NRC, the new model can be used to calculate the likelihood of various levels 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, it said but added the calculations, however, aren’t 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, it said.

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.