Q: The experts say that the chances are low that Georgia, near the Charleston fault, would ever get an earthquake over a magnitude of 6. What level of magnitude were Georgia’s nuclear plants designed to withstand?
—Tim Conner, Austell
A: Georgia's nuclear plants, like every nuclear power plant in the U.S., were designed to withstand an earthquake equal to the plant's maximum projected seismic event while fully complying with federal regulatory limits that ensure public safety, Christy Ihrig, a Georgia Power spokeswoman, told Q&A on the News. U.S. plants are not designed to a one-size-fits-all standard, but according to the geology of the specific site and area, David McIntyre, spokesman for the U.S. Nuclear Regulatory Commission, told Q&A on the News. A Commission document issued after the Japan earthquake (at http://nrc.gov/japan/faqs-related-to-japan.pdf) explains that existing nuclear plants were designed to account for the largest earthquakes expected in the area. The standards are not based on magnitude of an earthquake, but ground movement, a function of magnitude and distance from the epicenter, McIntyre wrote. Plants Hatch and Vogtle exceed all requirements issued regarding seismic activity and could withstand up to almost two times their requirements, Ihrig wrote in an e-mail. The seismic designs are well above the maximum historically known ground motion ever experienced at these sites, Ihrig wrote. She added that there is no direct correlation of earthquake magnitude to seismic ground motion. "Earthquake magnitude is a different earthquake measure; magnitude represents the total seismic energy released at the source," she wrote. Both plants are equipped with seismic activity monitors set at extremely low levels to offer important early indicators that may affect plant safety.
Lori Johnston wrote this column. Do you have a question about the news? We’ll try to get the answer. Call 404-222-2002 or e-mail q&a@ajc.com (include name, phone and city).
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