Days after a magnitude 5.9 earthquake shook the East Coast, the U.S. Nuclear Regulatory Commission has revealed that one of the most impacted nuclear plants may not have been built to sustain such a disruption.

Dominions (D) North Anna station located near Louisa, Va., the closest nuclear plant to the earthquakes epicenter, was the first to declare unusual events in the aftermath of last Tuesdays quake.

It was followed by nine others.

The station, which is located about 40 miles northwest of Richmond, saw its two units automatically shut after the facilities lost offsite power. It began running on emergency diesel generators to continue cooling the reactors until power was restored hours later.

The site remains closed nearly a week after the earthquake, and the NRC says it will continue as such until all damages are assessed and the company can demonstrate that no functional damage occurred to those features needed for its continued safe operation.

While no significant damage to safety system has been identified, Dominion has reported to the NRC that initial reviews determined the plant may have exceeded the ground motion for which it was designed.

The determination follows preliminary examinations from the NRC, although data is still being collected and analyzed to determine the exact level of shaking experienced by the station.

Further reviews by the NRC suggested further inspection was warranted. The agency has formed a group, called an augmented inspection team (AIT), comprised of technical experts from NRC headquarters.

Led by NRC Region II Branch Chief Mark Franke and North Anna Senior Resident Inspector Greg Kolcum, the AIT will begin work on the North Anna station on Tuesday.

The fact that were sending an AIT should not be interpreted to mean that Dominion staff responded inappropriately or that the station is less safe as a result of the quake, said NRC Region II Administrator Victor McCree.

Rather, he noted, the AIT provides the nuclear commission resources needed to completely understand all the effects at North Anna as part of its continued evaluation of earthquake risk at all U.S. nuclear plants, he said.

The group will hold an exit meeting with the company and other members of the public once it completes the initial inspection to discuss its findings.

The other nuclear plants located through New Jersey, Pennsylvania and Maryland that were impacted by the quake have all cancelled their unusual events alert and continue to operate normally.

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