Virginia quake may have exceeded nuclear plant design

WASHINGTON, (Reuters) – The historic earthquake that  shut Dominion Resources Inc’s North Anna nuclear plant in  Virginia last week may have shaken the facility more than it  was designed to withstand, the U.S. nuclear regulator said yesterday.

The Nuclear Regulatory Commission said it had sent a  special inspection team to the plant rocked by the  5.8-magnitude quake, after initial reviews from Dominion  indicated the ground motion may have exceeded North Anna’s  design parameters.

The plant cannot be restarted until the operator can show  no “functional damage” occurred to equipment needed for safe  operation, the NRC said.

“The company and the NRC will continue to carefully  evaluate information to determine if additional actions may be  necessary,” the regulator said in a statement.

It will probably take about three or four weeks before the  team’s preliminary findings are released, NRC spokesman Roger  Hannah said. He would not speculate on how long the plant might  be closed, saying it would depend on the team’s assessment.

If it does turn out that the quake exceeded North Anna’s  design specifications, Hannah said the team’s analysis could  find that the plant could withstand quakes stronger than what  was originally intended.

But the team could also call for changes such as back  fitting or reinforcing equipment for more powerful  earthquakes.

“It could be they would be shut down for a while, we just  don’t know at this point,” Hannah said.

Dominion said the North Anna reactors, which entered  service in 1978 and 1980, were designed for an earthquake of up  to 6.2 magnitude, but the NRC does not use that scale to  measure seismic design specifications. Instead, the commission  looks at ground-motion measurements.

Dominion spokesman Rick Zuercher said on Monday that more  will be known by midweek about whether the quake exceeded the  station’s design as further analysis is conducted on seismic  plates from the station’s containment building.

Zuercher said physical inspections of the plant have found  no major damage beyond cracks in office building walls, some  broken tiles, loose insulation on pipes and small damage to the  main transformer area where power is sent to the grid.

“We welcome the team to the site and will be sharing  information with them,” Zuercher said.

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