by Paula C. Squires
A team of six inspectors from the U. S. Nuclear Regulatory Commission (NRC) remained onsite Wednesday at Virginia’s North Anna Power Station in Louisa County in what is the beginning of a three-week review on how the nuclear-powered plant held up during last week’s 5.8-magnitude earthquake. The epicenter of the quake in Mineral is about 11 miles from the plant, owned by Dominion Virginia Power.
At issue is whether the quake’s ground motion exceeded the amount of shaking the plant was designed to withstand. The power plant’s nuclear units went online in 1978 and 1980. “Dominion has advised us from their on-site measuring devices that the quake may have exceeded the plant’s design basis,” said Joey Ledford, an NRC public affairs officer.
The quake knocked out off-site electrical power to the plant. After losing its connection to the grid, the stations’ two units automatically shut down as they were designed to do. While Dominion said the plant did not sustain major structural damage, it did declare an “unusual event,” along with 11 other nuclear- powered plants affected by the seismic activity, which was felt in 22 states. North Anna, however, was the only plant that shut down as a result of the quake.
The units remain shut down. Ledford said Dominion has not requested clearance at this point to restart them. “The fact that we’re sending an Augmented Inspection Team (AIT) should not be interrupted 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 in a statement.
The AIT helps the agency gather information for its continuing evaluation of earthquake risk at all U S. nuclear plants. After the thee-week review, Ledford said the NRC will hold an exit meeting with Dominion and a public meeting near the plant to discuss the findings. It also will issue a written report 30 days after the end of the inspection.
Ledford said the agency has not received “a great deal of expression of concern from the public about the inspection. “But we know the public is tuned in, because they have read the media reports ,and they care what happens. That’s one of the reasons our process calls for a public meeting.”
Richard Zuercher, a spokesman for Dominion Virginia Power, a subsidiary of Richmond-based Dominion Resources, said multiple inspections to date have found no damage to safety equipment.
“The reactors are shut down and in a safe condition. There continues to be no danger to the public,“ he said in an e-mail to Virginia Business.
According to Zuercher, Dominion engineers began inspecting the power station immediately after the earthquake and have found no significant damage to any nuclear structures, equipment, pipes, valves, pumps, the Lake Anna dam or any safety-related equipment.
The NRC team arrived Tuesday and will leave at the end of this week. They will spend a week in Atlanta and then return to the plant for a week in September to finish their report on the station’s seismic response.
“Preliminary analysis from station instruments showed that the quake caused ground force acceleration in the auxiliary building at higher frequencies that are greater than the station’s design basis. The auxiliary building is a support structure that does not house the reactors, but contains safety-related systems and equipment. We continue to evaluate all data points and should know by the end of this week if we exceeded the design of the station,“ Zuercher said.
As of this morning, Zuercher said Dominion had completed about 40 percent of the inspections associated with Unit 1, 29 percent of Unit 2, and 44 percent of civil engineering inspections of station structures.
“To date there has been no significant earthquake-induced damage in safety related structures or systems important to safety and shutdown cooling,“ he said.
“The only noteworthy damage is on the six bushing on the six main station transformers and on two spares. These are the transformers that send electricity produced by North Anna and place it on the grid. We are in the process of replacing these bushings.“ He added that Dominion is proceeding with civil inspections on all structures, including pipe supports and hangers. “
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