A dispute between the state of Vermont and a Louisiana-based power company moved to a federal appeals court Monday, when a panel of judges questioned lawyers but did not signal who they'll side with in the tussle over the future of Vermont's only nuclear plant.

David C. Frederick, a lawyer for Vermont officials, urged the 2nd U.S. Circuit Court of Appeals to overturn a lower-court judge who said last year that the Vermont Yankee nuclear plant can continue to operate after the Nuclear Regulatory Commission gave it a 20-year extension to operate. The judge, J. Garvan Murtha in Brattleboro, Vt., had ruled that the federal government controlled the plant's fate as it relates to safety issues. Vermont so far has refused to license the plant after a state permit expired last March.

Frederick insisted that the state had important non-safety reasons for seeking a fresh evaluation of the plant, including the "substantial costs" that would be incurred by taxpayers if the plant was decommissioned. Murtha had cited comments about safety that were made by legislators to show the state was primarily concerned with plant safety issues, which he found are solely the responsibility of federal regulators.