Waterford – Millstone Power Station’s Unit 3 reactor, which has been shut down for refueling, failed to restart properly Sunday night after key equipment failed.

The reactor was at about 2 percent power just before 6 p.m. Sunday when operators for Dominion, the Millstone owner, halted the startup after an auxiliary steam boiler shut off unexpectedly, causing a loss of vacuum conditions used to run a condenser, said Neil Sheehan, a spokesman for the Nuclear Regulatory Commission, and Dominion spokesman Ken Holt.

“They've had a number of issues trying to restart ... equipment issues,” Sheehan said. “There were no safety issues associated with the shutdown, but we would expect Dominion to fully understand what happened before they go back online.”