Operators at the North Anna Power Station manually shut down Unit 2 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 are 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.
North Anna workers fixed the problem that resulted in the feed-water pump shutting down, the company said.
North Anna 2 is expected to return to producing power soon, said company spokesman Richard Zuercher, though he could not be more specific.
The Nuclear Regulatory Commission (NRC) said the unit was stabilized at normal reactor temperature and pressure.