WATERFORD, Conn. (AP) — Federal regulators began an inspection of Connecticut's nuclear power plant Monday, more than a week after a power failure forced both units to shut down and water was found to be slightly radioactive.
The Nuclear Regulatory Commission announced it's examining the response by Millstone Power Station to the May 25 outage that lasted about six hours. Inspectors will look at equipment performance and evaluations by owner Dominion Resources Inc.
Specifically, inspectors will examine drainage from the reactor's coolant system and why equipment, known as a rupture disk, opened to relieve pressure.
"The question we have is, obviously, this should not be the normal sequence of events," said Neil Sheehan, spokesman for the Nuclear Regulatory Commission. "We have questions why this rupture disk had to open in the first place."
The health of plant workers was not affected, the NRC said.
Millstone supplies half of all power in Connecticut and 12 percent throughout New England.
For the first time, power was out at both Units 2 and 3 at the same time. A malfunctioning relay was blamed. Millstone declared an "unusual event" on May 25, the lowest of four levels of emergency classifications.
Frank Poirot, a spokesman for Connecticut Light and Power, said a team of investigators from the utility, New England's grid operator and Millstone are examining what happened and expect to file a report within four weeks.
Ken Holt, Millstone's spokesman, said four electrical lines were out: one due to service maintenance, another because of the faulty relay, a third that was affected by the relay and the fourth that stopped functioning because it could not handle the load for the entire power station.
Unit 2 has been back online since May 28, and Unit 3 is in final preparation to resume service, he said.
Five inspectors will be at Millstone for at least a week, Sheehan said.
Follow Stephen Singer on Twitter at https://twitter.com/SteveSinger10