Editor's note: The name of the Nuclear Energy Advisory Council has been corrected from a previous version.

Waterford — A pump considered one of the critical pieces of safety equipment at Millstone Power Station is being monitored closely after failing to operate correctly during one of three tests thus far in 2016. 

The turbine-driven auxiliary feedwater pump at Unit 3, which malfunctioned several times in 2013 and 2014, has been repaired since it failed during a test in February, Millstone spokesman Ken Holt said.

Repeated problems with the pump in 2013 and 2014 resulted in the plant receiving a “white” finding for a safety violation of “low to moderate” significance from the Nuclear Regulatory Commission.

After that, the plant was subjected to several special inspections and tested the pump frequently throughout 2015.

The NRC closed out the “white” safety finding in July, after determining that Millstone owner Dominion Resources had corrected the problems with the pump.

On Tuesday, however, the Nuclear Energy Advisory Council learned from NRC officials that the same pump failed again this year.

Council member Jeff Semancik, director of the Radiation Division at the state Department of Energy and Environmental Protection, said he was troubled to learn about continuing problems with the pump, and that additional attention is warranted.

“I’m concerned if they have any failures with that pump,” he said Wednesday. “I would have hoped the steps they took would have prevented this for a while. We do want to make sure this piece of equipment works reliably."

Louis McKown, NRC resident inspector at Millstone, told the council — a citizen panel that monitors the plant — that the pump passed all tests in 2015, but failed one of three times it has been tested this year.

Michael Scott, the NRC’s director of reactor projects, added that the agency will continue to focus on the pump to ensure that it is operating reliably.

The pump is “one of the top two most important safety systems” at the plant that would be needed if an accident were to occur, on par with the plant's emergency diesel generator, said David Lochbaum, director of the Nuclear Safety Project for the Union of Concerned Scientists.

The pump is essential to keeping the reactor cool if there is a loss of power, Lochbaum said. Unit 3 has three auxiliary pumps, two of which are motor-driven and need electricity to run.

The turbine-driven pump, however, can operate even after a loss of power, according to Holt, the plant spokesman. It can supply water to generators that make steam, drawing heat away from the reactor to keep it cool and prevent a meltdown.

“It’s an important piece of safety equipment,” he said. “We’re keeping an eye on it.”

After the problems in 2013 and 2014, he said, Millstone staff “took a very exhaustive look at the piece of equipment” and determined the problems were caused by a mislabeled replacement bearing.

The pump was rebuilt when Millstone 3 was shut down for routine refueling about 18 months ago, he added.

After the pump failure in February, Holt said, it was tested twice and operated correctly both times. He said a “root cause investigation” of the reason for the failure in February is nearly complete.

“Whenever it doesn’t perform correctly, we take it seriously,” he said.

Neil Sheehan, spokesman for the NRC, said the problems in February were attributed to “a binding in a bearing.”

To fix the problem, Millstone crews replaced the bearing, lubricated the replacement and made changes to a protective shield that may have caused the old bearing to stick, Sheehan said.

“As for the NRC, we are still evaluating the issue,” he said. “We expect to document the results of our assessment in an inspection report due out in May."

He noted that the pump worked successfully for about eight hours in January, when it ran during a reactor shutdown.

j.benson@theday.com