HOUSTON (Reuters) - Dominion Resources workers were inspecting the North Anna nuclear power plant in Mineral, Virginia on Wednesday, a day after an earthquake centered near plant knocked both reactors offline, the company said.
The company said several aftershocks were felt but had no impact on the plant, 80 miles southwest of Washington, which canceled its emergency alert on Wednesday afternoon.
"There will be an extensive walk-down, including inside the containment (vessel) once both units are in cold-shutdown," said Joey Ledford, a spokesman for the Nuclear Regulatory Commission's regional office in Atlanta.
"They will go over this with a fine-tooth comb, with our resident inspectors beside them, to make sure there is no damage of any kind," Ledford said.
Tuesday's 5.8 magnitude earthquake, the largest to hit the U.S. East Coast in 67 years, knocked out power to the nuclear plant which triggered an automatic shutdown.
Operators restarted coolant pumps for each reactor after off-site power was restored overnight.
NRC officials will assess damage, and also seismic data from the site to determine if the quake was stronger than the plant was designed to withstand.
That will be critical in determining how long the 1,806-megawatt station will remain shut, officials said.
"In light of the quake's strength and proximity to the plant, the NRC will soon decide whether to conduct a follow-up inspection, aimed at determining how the quake compares to what the plant was designed to withstand," the NRC said in a statement.
Seismic equipment that measured the tremor at the North Anna Station has been sent for a complete evaluation expected to take a few days, according to the NRC.
The agency has not decided whether to send a special team of inspectors to the plant, according to a release.
Dominion officials were not available to discuss seismic data. Spokesman Jim Norvelle had said the North Anna reactors, which entered service in 1978 and 1980, were designed to withstand an earthquake of up to 6.2 in magnitude.
Dominion reported no "major" damage to the facility on Tuesday as diesel generators were started to keep the reactors' radioactive cores cool until off-site power was restored in a few hours.
North Anna is unlikely to be affected by the approach of Hurricane Irene as it moves up the East Coast, NRC officials said.
Other nuclear stations, however, including Dominion's Surry plant in Virginia and Progress Energy's Brunswick Station on the North Carolina coast, are preparing for the storm, NRC officials said.
Owners of 12 other nuclear power plants that also felt Tuesday's quake, including Exelon Corp, Public Service Enterprise Group, American Electric Power Co,
Constellation Energy, PPL Corp; Entergy Corp and Progress Energy have canceled emergency event warnings after inspections for quake-related damage.
These plants were: Peach Bottom, Three Mile Island, Susquehanna and Limerick in Pennsylvania; Salem, Hope Creek and Oyster Creek in New Jersey, Calvert Cliffs in Maryland, Surry in Virginia, Shearon Harris in North Carolina and D.C. Cook and Palisades in Michigan.
(Reporting by Eileen O'Grady in Houston and Roberta Rampton in Washington; Editing by David Gregorio)