Dominion (NYSE:D) said Dec. 23 that it has removed Unit 1 of its North Anna nuclear facility from service to repair a “very small leak of water” water in a pipe that is normally used to drain water from the reactor coolant system during refueling outage maintenance activities.
Plant operators on the afternoon of Dec. 22 had reduced Unit 1 to 30% power to enable workers to enter the containment building and inspect the reactor coolant system for water leakage, after station sensing devices had detected the condition, according to a statement from a Dominion spokesperson.
North Anna 1 was listed in federal records at zero generation early Dec. 23, while North Anna 2 was listed at 100% generation. The units, operated by Dominion utility subsidiary Virginia Electric and Power, are 900-MW-plus pressurized water reactors (PWRs) located in Louisa County, Va.
The affected pipe — which is about 2 inches in diameter — developed a leak of less than 5 one-hundredth of a gallon per minute. Because the area of the pipe where the leak occurred is not located at a valve, operators could not isolate the leak to repair it, and were required by their operating procedures to shut the unit down to do so.
The Nuclear Regulatory Commission (NRC) was notified of this condition as it affected the pressure boundary of the reactor coolant system, which must be maintained at zero leakage. The situation was noted in NRC’s daily “event notification report.”
This condition did not pose any safety threat to the employees at the station or the public, Dominion said. The company expects to return the nuclear unit to service “soon” once repairs are made.