Iowa’s only nuclear power plant was shut down early Sunday morning. Maureen Brown is a spokesperson for the company that manages the Duane Arnold Energy Center in Palo, Iowa northwest of Cedar Rapids. She says operators shut the plant down when a valve that regulates water flow malfunctioned. Brown says the valve should be replaced soon, but she declined to be specific on the time frame.Brown says she’s prohibited about talking about power plants, and the power grid, because of a number of “power market sensitivities.” Brown also said she was hesitant to characterize the problem as major or minor, she simply says plant operators took appropriate action in responding to the problem. The plant is owned by Alliant Energy, but is managed by the Nuclear Management Company of Hudson, Wisconsin.