The Brattleboro Reformer reported this afternoon:
Vermont Yankee nuclear power plant in Vernon is on its way back up to full power after it powered down for a control rod adjustment on Monday.
A rod adjustment is performed every three months to keep the reactor operating at optimal power production.
During the power down, the plant’s turbine stop valves were tested and one of the valves malfunctioned.
“When we power down for a rod pattern adjustment there is required surveillance to be done, including surveillance on the four turbine stop valves,” said Larry Smith, Yankee’s manager of communications. “We were testing one of the valves and it closed as it supposed to but it did not reopen. We still had three operational valves.”
One expert on nuclear operations said that the event would have been more serious if the valve had malfunctioned while the plant was operating at full power:
“The sudden stop of the steam train sends a pressure pulse back to the reactor,” said David Lochbaum, the director of the Union of Concerned Scientists’ Reactor Safety Project. “There’s an automatic reactor scram signal if the turbine trips at power levels above the capacity of the turbine bypass valves.”
Such a malfunction did close Vermont Yankee on a previous occasion:
In 2007, a failure in the turbine stop valves caused an emergency shutdown of the reactor. The problem was attributed to the lack of preventative maintenance on a valve bell crank mechanism.
The single unit at Vermont Yankee is a General Electric boiling water reactor with the same containment structure as Fukushima Daiichi. Vermont Yankee came on line in 1972, and has been at the center of a bitter license extension process.
Here’s a link: http://www.reformer.com/ci_19877673?source=most_viewed