Feed-water pump problems led to the shut down of one reactor at Dominion Virginia Power’s North Anna nuclear plant Sunday.
While concerns about another type of pump have prompted a special federal inspection at a Connecticut nuclear station operated by the utility’s parent company, Dominion Resources Inc.
Operators at the North Anna Power Station manually shut down Unit 2 Sunday morning because of an electrical issue with one of the station’s pumps that ensure continuous flow of water used for steam production and reactor cooling, the utility said.
A backup feed-water pump on North Anna 2 automatically started, the company said, but an indication light in the control room that would have alerted operators that the backup was working did not come on.
Two feed-water pumps end up required to maintain flow to each of the unit’s three steam generators. “The operators made a conservative decision to manually shut down the unit,” Dominion Virginia Power said.
“All systems responded to place the unit in a safe and stable condition,” the company said.
North Anna workers fixed the problem that resulted in the feed-water pump shutting down, the company said.
North Anna 2 should return to producing power soon, said company spokesman Richard Zuercher, though he could not be more specific.
The federal Nuclear Regulatory Commission (NRC) said the unit ended up stabilized at normal reactor temperature and pressure.
Dominion Virginia Power’s four nuclear reactor units — two at North Anna and two in Surry County — normally provide more than 40 percent of the utility’s electricity.
The NRC also has begun a special inspection at Dominion Resources’ Millstone Unit 3 nuclear power plant in Waterford, CT, because of a series of problems with a pump that is part of a reactor safety system.
The inspection began Monday at the plant operated by Dominion Nuclear Connecticut Inc., a subsidiary of the Richmond-based energy corporation.
The inspection, conducted by a four-member team, will focus on a turbine-driven auxiliary feed-water pump, the NRC said.
Since May, the pump experienced unexpected speed oscillations, most recently on Jan. 23.
“The fact that these issues occurred on multiple occasions despite repeated efforts to repair this component has prompted us to take a closer look at the situation,” said the NRC’s regional administrator, Bill Dean.
The team will document its findings in a report to come out within 45 days of the end of the review, the NRC said.
The backup feed-water system is one of several that help cool the reactor following a shutdown by pumping water into the plant’s steam generators.
Steam generators are large heat exchangers that convert the reactor’s heat into steam, which spins the plant’s turbine and generates electricity.