(Host) The Vermont Yankee nuclear plant shut down unexpectedly this afternoon and officials are investigating the cause.
The shutdown occurred during testing of a steam valve. A Yankee spokesman said the plant is safe and stable.
Meanwhile, federal regulators are expanding their review of last week’s collapse of a cooling tower at Vermont’s only nuclear plant.
VPR’s John Dillon is following the story.
(Dillon) A nuclear plant is designed to shutdown automatically when the equipment detects something wrong.
That’s what happened at 3:12 Thursday afternoon. The plant control systems kicked in and brought the reactor to a halt.
Diane Screnci is a spokeswoman for the Nuclear Regulatory System.
(Screnci) "The plant responded as expected so all of the safety systems worked once the plant shut itself down."
(Dillon) Screnci said the NRC has inspectors on site who will help determine why the shutdown occurred.
The state Department of Public Service, which represents consumers, is also in close contact with plant officials.
Public Service Commissioner David O’Brien said the automatic shutdown happened at the same time as plant operators were testing a steam valve.
(O’Brien) "The two occurrences ran together. That doesn’t necessarily mean one caused the other. It’s possible, but we just don’t know that."
(Dillon) This has been a troubled two weeks for Vermont Yankee. A cooling tower partially collapsed last week, forcing the plant to throttle back its power production.
And federal regulators told the plant this week that they want to know more about the tower failure.
NRC spokesman Neil Sheehan said the questions concern the plant’s attempt to extend its operating license.
(Sheehan) "We are now asking the company to provide us with more information about why all of the cooling towers that were in the bank of towers that had that partial collapse were not part of the license renewal application."
(Dillon) Entergy, the company that owns Vermont Yankee, wants to run the reactor for another 20 years beyond 2012.
And Entergy told federal regulators before the accident that they don’t need to look at most of the cooling towers as part of the extensive license renewal process.
But after the tower collapsed last week, the NRC began asking more questions.
Sheehan said that initially Yankee said that only two of the 11 cooling tower cells should be part of the license review.
The NRC now wants to know if that assumption is still valid.
(Sheehan) "We want to ensure that if this plant is going to operate for an additional 20 years that those systems, structures and components are capable of doing so safely for that additional period of time."
(Dillon) Yankee has 30 days to respond to the NRC.
For VPR News, I’m John Dillon in Montpelier.