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The containment door of the Unit 2 reactor, opened for maintenance is 7 feet thick of reinforced concrete. Photo by Michael Mercier/ The Huntsville Times

The Nuclear Regulatory Commission later this year will provide nuclear plants with a seismic analysis software tool and require all of the nation's 104 reactors to assess their earthquake risks.

NRC announced the plan Thursday, two days after a 5.8 quake rattled the East Coast and shut down the North Anna nuclear facility near the quake's epicenter in Mineral, Va.

The plant declared an "alert" - the second-lowest of NRC's four emergency classifications - before regaining its electricity several hours later.

Another dozen nuclear power plants along the East Coast and upper Midwest declared an "unusual event," the NRC's lowest emergency classification. All 12 resumed normal operations by the end of Tuesday.

NRC spokesman Joey Ledford and Tennessee Valley Authority spokesman Ray Golden said it is too early to know the effects of the new tool and the reviews, either for TVA or the nation's 60 commercial nuclear power plants.

Ledford said the NRC began working on a new assessment tool some years ago.

"We have been re-evaluating seismic issues since long before the [Fukushima Dai-ichi] event in Japan, much less the Virginia earthquake," he said. "This long-standing initiative was launched when new data became available indicating that seismic risks in the eastern and central parts of the country might be greater than earlier estimates."

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Ray Golden

Since the 9.0 Japan quake and tsunami threw the Fukushima Dai-ichi plant into crisis with partial meltdowns and continuing radioactive releases, the NRC has come under fire for not moving faster on new assessments for plants built decades ago.

Last week, the criticism increased when Rep. Edward Markey, D-Mass., wrote to the NRC.

"The Virginia earthquake is now our local 911 call to stop delaying the implementation of stricter safety standards," Markey's letter states.

TVA's Golden said utilities have known this was coming for some time.

"They [NRC] looked at this new data and said, 'This gives us a reason to re-examine seismic analyses at central and eastern nuclear plants,'" he said. "Also, they did come out and say there was nothing in this new data that caused them to feel they needed to require immediate action be taken at any given site."

Golden said TVA's nuclear plants are designed to withstand earthquakes up to a certain size.

Earthquakes are routinely measured by magnitude, or energy released. But the NRC requires reactors to withstand a predicted level of ground motion triggered by the energy release.

Golden said Sequoyah, Watts Bar and Bellefonte are designed to withstand motion that equates to a 5.8 magnitude quake.

Brown's Ferry is designed to withstand the action of a 6.0 quake.

Golden said things may be done at TVA's nuclear plants to enhance their safety seismic standards if such a need is found.

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