Seismic models allow U.S. nuclear facilities to reassess seismic risk

A new seismic model allows U.S. nuclear facilities in the central and eastern United States to reassess their seismic hazards.
The model and report, The Central and Eastern United States Seismic Source Characterization for Nuclear Facilities, was a joint effort by the Electric Power-Research Institute, the U.S. Department of Energy and the U.S. Nuclear Regulatory Commission (NRC).
The study is the first major update to the model since the 1980s. The March 2011 disaster at Japan’s Fukushima Daiichi nuclear plant and a quake in Virginia in August 2011 lent urgency to the initiative.
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, an EPRI release says.
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, an EPRI release says.
EPRI goes on to note that the calculations do not automatically equate to a nuclear power plant’s overall risk. The information is to be combined 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 the largest predicted ground motions could occur in the vicinity of repeated large magnitude earthquake sources such as New Madrid, Missouri and Charleston, South Carolina.