RICHMOND, Va. — Dominion Virginia Power's North Anna Power Station, the first operating U.S. nuclear plant shut down because of an earthquake, can restart after being offline since the Aug. 23 tremor that shook millions along the East Coast, the U.S. Nuclear Regulatory Commission said Friday.
The two nuclear reactors at the plant about 11 miles from the quake's epicenter automatically shut down after the 5.8-magnitude earthquake caused peak ground movement about twice the level for which it was designed.
Multiple inspections done by both Dominion and federal regulators show the plant's twin 1,800-megawatt reactors and other safety components did not suffer any functional damage during the temblor. Dominion has spent more than 100,000 hours and $21 million in inspection, testing and evaluation at the power station about 50 miles northwest of Richmond.
The plant did experience some cosmetic damage ranging from small buckles and cracks in tile floors in one of its technical buildings, to bolts of large metal parts that transfer power from transformers to the electrical grid and into homes. The quake also caused 25 massive nuclear storage containers at the plant to shift, but they remained intact.
"We're satisfied the plant meets our requirements to restart safely, and we'll monitor Dominion's ongoing tests and inspections during startup of both reactors," Eric Leeds, director of the NRC's Office of Nuclear Reactor Regulation, said in a statement.
Leeds said because the earthquake shook the reactors more strongly than the plant's design anticipated, Dominion had to prove that the quake caused no functional damage to the reactors' safety systems.
In making the decision to allow the reactors to be restarted, the NRC said its staff reviewed Dominion's findings and conducted its own inspections. The agency paid close attention to the plant's piping systems, nuclear fuel assemblies, steam generators, pumps and valves, and emergency diesel generators.
Shortly after getting the go-ahead from the agency, control room operators, under the oversight of Dominion and NRC inspectors, initiated the restart process Friday for one of the reactors.
Dominion said it expects it will take about 10 days for the plant to be fully operational as both reactors will be restarted in phases and testing of all safety equipment and inspections of containment areas will be done during that process. The company also said it plans to have additional staffing at the plant during the restart.
"As always, safety is our first priority," said David Heacock, president and chief nuclear officer of Dominion Nuclear, said in a statement.
It will first start Unit 1, gradually raising the water temperature to 580 degrees Fahrenheit and increasing the pressure to 2,250 pounds per square inch over six days. The restart process for the second unit also will start during that time in order to bring both reactors to 100 percent and provide electricity to the transmission grid.
Various groups have said the quake and subsequent shutdown at North Anna Power Station brought attention to the danger of another event in the area. Some have asked Dominion to retrofit the two reactors to higher earthquake safety standards.
The NRC has said it plans to order all U.S. plants to update their earthquake risk analyses, a complex exercise that could take two years for some plants. The review, launched well before the East Coast quake and the Japan nuclear disaster in March, marks the first complete update to seismic risk in years for the nation's 104 existing reactors, despite research showing greater hazards.
The two North Anna reactors are among 27 in the eastern and central U.S. that may need upgrades, according to a preliminary NRC review.
When fully operational, the Virginia facility produces enough energy to power about 450,000 homes. Dominion had been using other power sources in its generation system or is buying power to make up for the plant being offline.
The company is still weighing the addition of a third reactor at the Louisa County power plant but has not yet committed to move forward. The company will reassess when it receives operating approval from the NRC, expected in 2013.
Dominion Virginia Power is a subsidiary of Richmond-based Dominion Resources Inc., one of the nation's largest producers and transporters of energy and has the nation's largest natural gas storage system. It serves retail customers in 15 states.
Michael Felberbaum can be reached at . http://www.twitter.com/MLFelberbaum