The Dominion (NYSE:D) Millstone 2 nuclear unit in Connecticut experienced an unplanned outage on Aug. 11, according to a report filed with the Nuclear Regulatory Commission (NRC).
Millstone Unit 2 was still listed at zero power early Aug. 12, according to NRC data.
“Reactor operators manually tripped the reactor due to the loss of two out of four circulating water pumps which caused a drop in condenser vacuum,” according to the NRC report.
“The reactor is shut down and stable with decay heat removal via steam dumps to the condenser. The cause of the circulating water pump trips is currently unknown, but initial indications are that the pumps tripped due to a lightning strike that caused an electrical perturbation,” according to the report. “The reactor will remain shut down while the licensee investigates the cause.”
Millstone Unit 3 remains at full power.
“Operators at Millstone Power Station removed Unit 2 from service Thursday morning because two of the unit’s four circulating water pumps automatically shut down,” Dominion said in a statement. “The circulating water pumps deliver water from Long Island Sound that is used to condense steam back into water as part of normal plant operations,” the company said.
There was no threat to the safety of the public and no release of radioactivity occurred, Dominion added.
Millstone 2 and 3 are pressurized water reactors (PWRs) located in New London County, Connecticut. Together they have a generating capacity of more than 2,100 MW.