Regulators Calls for Further Investigation at Earthquake-Affected Plant in Virginia

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The Nuclear Regulatory Commission is sending more inspectors to a Virginia nuclear power plant to further review what damage last week's 5.8 magnitude earthquake may have caused.

The NRC is sending the inspectors to the North Anna station near Louisa, Va., about 40 miles northwest from plant operator's Dominion's Richmond headquarters. The plant is less than six miles from the August 23 earthquake's epicenter in Mineral, Va.

The NRC stressed that the expanded investigation does not necessarily mean the plant is any less safe, but they have formed an Augmented Inspection Team to conduct the investigation.

According to the NRC, an AIT is formed by the NRC "to review more significant events or issues at NRC-licensed facilities." This is an additional investigation after the NRC initially sent a seismic expert and another structural expert, according to an NRC statement released Monday, to "assist the agency's resident inspectors on site."

The agency reported that "no significant damage to safety systems has been identified," but the plant's operator Dominion Power has reported to the NRC that "initial reviews determined the plant may have exceeded the ground motion for which it was designed."

The plant's two units were automatically shut down after the station lost offsite power following the earthquake and emergency diesel generators were used to cool the reactors until offsite power was brought back. In the release, the NRC said the investigation will "determine the precise level of shaking that was experienced at key locations within the North Anna facility."

The NRC requires that the plant not re-start "until it can demonstrate that no functional damage occurred to those features needed for continued safe operation."

Members of the surrounding communities should not worry and the plant remains in "cold shutdown," Roger Hannah, senior public affairs officer at the NRC, told ABC News.

"Based on all the information so far there doesn't appear to be any damage to major safety systems or systems that would prevent a radiological release," Hannah said. "What they are continuing to do is look at how severe the earthquake was and if it exceeded what the plant was designed for."

Hannah said that Dominion and NRC workers checked the safety of the plant "immediately after the earthquake" doing "a very careful walk down" where they found "no indication that any of the safety systems were damaged." A "walk down" is what members of the industry call the initial inspections.

Hannah added that the NRC will be doing further analyses to see if the plant can withstand a larger quake than the range it now can currently withstand.

Jim Norvelle, a spokesman for Dominion Power, explained that the range is roughly between a 5.9 to a 6. 2 on the Richter scale, but they actually measure earthquake damage via ground force acceleration, which measures the intensity of an earthquake at a specific geological location and it measures east, west, north, sound and vertical while a Richter scale measures the magnitude of an earthquake at the epicenter.

Norvelle told ABC News that the part of the nuclear plant that is built on rock is designed to withstand 0.12 g or about 5.9 on the Richter scale and the portion of the station built on soil can withstand 0.18 g or about 6.2 on the Richter scale. Norvelle added that there is always a "safety margin" in play that goes above those numbers.

Norvelle agreed with the NRC that there has been "no significant damage" from the earthquake including to any of the station's "pumps, valves, pipes, support structure, or safety equipment."

"What we have found is some thermal insulation shook off pipes. Some equipment on the electric transformers needed to be replaces. We have seen cracking in a wall of a commercial grade building, an office building adjacent to the power station," Norvelle explained. The office building is not built to the same standards as the nuclear plant.

Norvelle said Dominion is "fully cooperating" with the NRC and the NRC's team will be onsite for one week and then will return for a second week after which a public exit meeting will be held to tell the community about what they found in their investigation. Norvelle said members of the community are welcome to come with questions and concerns.

Edwin Lyman, a nuclear physicist with the Union of Concerned Scientists nuclear safety project, is pleased that the NRC is conducting a further investigation before the plant starts operating again. Lyman says the NRC should "thoroughly analyze and investigate" the plant for any problems with the "safety equipment that could be affected by the shaking."

Lyman says he doesn't believe the North Anna station is an "immediate hazard," but that the continued investigation sheds light on a larger worry.

"It does illustrate a concern that we have and that has really come to light after Fukushima that there is incomplete knowledge how nuclear plants can withstand earthquakes they experience over the next several decades," Lyman said. "There is growing knowledge that nuclear plants in the central and eastern United States may be vulnerable to more severe earthquakes than was previously thought and the NRC and the industry are not moving fast enough to deal with that information."

Dominion told ABC News they will thoroughly evaluate the results of the investigation before reopening the plant.

"We all want to demonstrate to the NRC this power station is safe to operate and we have to do that before we think about restarting the units," Norvelle said.

ABC News' Brian Hartman contributed reporting.