The historic earthquake that shut down Dominion Resources Inc’s North Anna nuclear plant in Virginia last week may have shaken the plant more than it was designed to withstand, the U.S. nuclear regulator said on Monday.
The U.S. Nuclear Regulatory Commission said it has dispatched a special team of inspectors to the Virginia plant that was rocked by the 5.8 magnitude earthquake last week, after initial reviews from Dominion indicated the ground motion may have exceeded the plant’s design parameters.
The North Anna plant cannot be restarted until the operator can show that no “functional damage” occurred to equipment needed for the 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.
After the earthquake last week, 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 about whether the quake exceeded the station’s design by midweek as further analysis is done 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.
The NRC has been reviewing the ability of U.S. plants to cope with major disasters after a massive earthquake and tsunami nearly led to a complete meltdown at Japan’s Fukushima nuclear complex earlier this year — the world’s worst nuclear crisis since Chernobyl.
An NRC task force set up in the aftermath of the Japan crisis urged a shift in the NRC’s safety regime that would force plants to plan for catastrophes far worse than design specifications allowed for, as well as require that companies assess seismic and flooding hazards at plants every 10 years.
Critics have urged the NRC to move more quickly to adopt these changes to ensure plants are prepared for disasters, with last week’s earthquake further fueling these calls.
“The fact that we’re sending an [augmented inspection team] should not be interpreted to mean that Dominion staff responded inappropriately or that the station is less safe as a result of the quake,” NRC Region II Administrator Victor McCree said.
McCree said the team will help the commission understand the effects of the quake on North Anna and gather information that will help the NRC’s evaluation of earthquake risks at all U.S. nuclear plants.
(Reporting by Ayesha Rascoe; additional reporting by Eileen O’Grady; Editing by Bob Burgdorfer and Alden Bentley)