The Unit 2 reactor at Millstone Power Station is repowering after a brief shutdown.
The reactor was at 18-percent power this morning and is expected to be at full power in another day or so, said Ken Holt, a spokesman for Millstone owner Dominion.
Operators were returning the reactor to power earlier this week after repairing an oil leak when one of two main feedwater pumps lost suction and shut down.
A preliminary look into the cause found that one pump lost suction and shut off as workers were bringing the other pump into service, Holt said. That reduction of suction may have been caused by a variety of procedural changes made over the years to improve the efficiency of the feedwater system, Holt said.
The feedwater pumps are used to pump water from the plant's condensate system to the steam generators. The water is "fed" into the steam generators, converted to steam, and the steam is piped to the turbine, which it spins to generate electricity. The steam is then condensed back into water, which is filtered and heated, and sent back to the pumps, where the cycle begins again.
“We’re looking at procedures and making changes where we need to,” Holt said. “We’re also conducting operator training to raise awareness of similar situations so (operators) can respond efficiently.”
A more thorough “root cause” investigation starts Monday, he said.