BRATTLEBORO -- Power output at Vermont Yankee nuclear power plant in Vernon was decreased to 83 percent early Tuesday due to low flow and higher temperatures in the Connecticut River. By Tuesday afternoon, power output was back up to 92.6 percent.
Because of river conditions, the plant was switched over to closed-cycle cooling utilizing the plant's cooling towers to cool the water necessary to prevent the plant's reactor from overheating.
"In this kind of hot and humid weather with low river flows, we reduce power to insure the plant's systems remain within administrative limits," said Rob Williams, spokesman for Yankee.
While the plant can operate at 100 percent while the cooling towers are in use, its output to the grid is reduced because some of the power is used to run the fans in the towers.
"Sometimes in the summer, the weather dictates how much electricity we can supply to the grid," said Williams. "That's the nature of doing business on a river with variable flow and variable temperature."
In addition, Yankee is restricted by conditions in a state discharge permit from increasing the river's water temperature when the ambient temperature reaches a certain point.
On Aug. 21, 2007, one of the cooling fan cells collapsed due to rotten wooden support members. Entergy representatives told the Nuclear Regulatory Commission that inspection and maintenance procedures needed to be updated.
Yankee has been operating for 260 days since its last refueling outage.
Bob Audette can be reached at email@example.com, or at 802-254-2311, ext. 160.