Stuck Valve Reduces Nuke Power

Friday, February 3, 2012 @ 11:02 AM gHale

Vermont Yankee nuclear power plant reduced power for two days because of a problematic valve in a turbine in the non-nuclear side of the plant.

Vernon, VT-based Vermont Yankee was at 43 percent power, but was increasing power production, Entergy Nuclear spokesman Laurence Smith said late Wednesday. On Tuesday, the reactor was at 20 percent, and earlier Wednesday, it was at 34 percent, according to the morning report posted by the Nuclear Regulatory Commission (NRC) on its website.

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Smith said plant personnel were performing scheduled maintenance surveillance of the turbine valves when the problem occurred. He said the valve closed properly, but would not “respond as expected” and reopen.

Engineers from Vermont Yankee and General Electric performed repairs on the 640 megawatt reactor, Smith said.

He said the problem was with a pilot valve on the main valve on the B turbine.

The problem traced back to a lack of lubrication, said Neil Sheehan, a NRC spokesman.

“They identified a lack of lubrication on the pilot (control) valve for the stop valve,” Sheehan said.

Turbine stop valves are swing disc-type valves on the lines carrying steam from the reactor to the turbine, he said, and they should abruptly close when the reactor trips, or shuts down, causing the turbine to slow down and eventually stop.

Sheehan said the valve problem occurred in what the NRC considered was the “non-nuclear” side of the plant, meaning the power-generating side of the plant.

“Problems involving the turbine can force a shutdown, which can challenge plant operators,” he added.

Entergy employees used the reduced power time to clean the water box of the plant’s condenser, Sheehan said, adding the water box, at the base of the condenser, needs periodic cleaning.



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