Dominion Virginia Power has begun restarting reactors at its North Anna Power Station after receiving clearance from the Nuclear Regulatory Commission.
The plant’s two reactors were tripped offline when a 5.8-magnitude earthquake occurred about 11 miles from the plant in Mineral on Aug. 23. The event marked the first time in the U.S. that a quake had knocked a nuclear plant offline.
Under the oversight of Dominion nuclear officials and NRC inspectors, control room operators today began the restart process for North Anna’s Unit 1. Dominion will bring Unit 1 on line first and then begin the restart of Unit 2. Both units will return to 100 percent power in about 10 days.
The company said the restart process for each unit normally takes about four days from cold shutdown to normal power operations. During the restart process, hundreds of pumps, motors, valves and other systems are restarted in a carefully prescribed sequence. Because the units will be starting up after the first earthquake to shut down a nuclear unit, the restart process will be prolonged to allow for additional equipment tests, Dominion officials said.
The NRC announced today that the reactors were cleared to restart after a series of inspections and public hearings.
“The earthquake shook the reactors more strongly than the plant’s design anticipated, so Dominion had to prove to us that the quake caused no functional damage to the reactors’ safety systems,” Eric Leeds, director of the NRC’s Office of Nuclear Reactor Regulation, said in a statement. “We’ve asked Dominion dozens of detailed questions, and our experts have examined Dominion’s answers as well as information from our own inspections. 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.”
When the earthquake occurred, the plant shut down safely and was powered by diesel generators for a few hours. The NRC said it monitored the situation, observed plant inspections and assessed quake data. On Aug. 29, the agency sent an “augmented inspection team” to the plant to further review the effects of the earthquake. A restart readiness inspection was held in mid-October.
Inspections by both Dominion and the NRC concluded that the plant suffered only minor damage from quake, which did not affect its safety systems. NRC held public hearings on its findings on Oct. 3 and Nov. 1.
In a letter to Richmond-based Dominion, the NRC detailed several follow-actions by the company, including
• Updating the plant’s “Final Safety Analysis Report” to incorporate information from the quake;
• Gathering additional information on the fault responsible for the quake and ground motion effects at North Anna;
• Re-evaluating plant equipment (including an assessment of potential improvements);
• Developing any needed inspections or evaluations for components within the North Anna plant; and
• Permanently updating seismic monitoring equipment for the North Anna reactors and dry-cask spent fuel storage facility.
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