An investigation into the failure of one of North Anna nuclear plant’s four emergency diesel generators following last summer’s earthquake has alleged that plant personnel did not establish and maintain appropriate maintenance procedures for the plant’s generators. Dominion’s plant near Richmond, Va., faces increased regulatory oversight as a result, the Nuclear Regulatory Commission (NRC) said on Monday.

The NRC said the violation was a "white" finding, meaning it has low to moderate safety significance. "The failure was not caused by the earthquake and repairs were completed a short time later," the commission said. "Ensuing inspections determined that the plant’s maintenance procedures did not provide adequate guidance for installing specific gaskets on the generators. Dominion has since revised its maintenance procedures."

The two nuclear reactors at North Anna Power Station automatically shut down following a 5.8-magnitude earthquake in Central Virginia on Aug. 23, 2011. The epicenter was approximately 11 miles west-southwest of the station.

The NRC’s finding puts North Anna into the Regulatory Response Column on the NRC Action Matrix, meaning the plant will be subject to additional NRC inspections beyond the baseline inspections that are conducted at all nuclear plants.

On Monday, the NRC also said it would increase oversight of Florida Power & Light’s (FPL’s) St. Lucie Unit 1 in Jensen Beach, Fla., a reactor that has seen several scrams since the third quarter of 2011.

Unit 1 crossed the green-to-white threshold for Unplanned Scrams per 7,000 Critical Hours performance indicator due to one trip in the third quarter of 2011, one trip in the fourth quarter of 2011, and one trip in the first quarter of 2012. "In addition, the review identified that the Unplanned Scrams with Complications performance indicator also crossed the green-to-white threshold. This was due to one complicated trip in the third quarter of 2011 and one complicated trip in the first quarter of 2012," the NRC said.

“Overall, the St. Lucie plant continues to operate safely,” said NRC Region II Administrator Victor McCree. “However, these shutdowns point to performance issues and a trend that needs to be addressed.”

The NRC evaluates inspection findings and performance indicators at commercial nuclear power plants with a color-coded system that classifies them as green, white, yellow, or red, in increasing order of safety significance. As the significance increases, the NRC heightens the level of oversight for that plant. If a plant takes appropriate corrective actions and improves safety performance, the agency returns to its normal, but still extensive, inspection schedule.
Sources: POWERnews, NRC