The Vermont Department of Health said it found detectable traces of radioactive tritium in the Connecticut River that it said came from the 510 MW Vermont Yankee nuclear power plant.

“We have been tracking the plume of tritium-contaminated groundwater as it moves slowly toward the river, and this new finding confirms that tritium has traveled from the Yankee site to the Connecticut River,” Health Commissioner Harry Chen said in a statement.

The department’s laboratory said it confirmed that samples of water taken on July 18 and July 25 from points where groundwater flows into the river measured 534 and 611 picocuries per liter, just above the lower limit of detection.

Reuters reported that plant owner Entergy Corp. (NYSE: ETR) said it tested the same river water samples and found levels below the minimum detectable limit.

The Health Department also reported that Strontium-90 was detected in edible portions of fish taken nine miles upstream of the nuclear plant in June 2010. Lab results released on August 17, 2011 confirmed the accuracy of that finding, reports said.

Vermont Governor Peter Shumlin told plant officials on August 3 to increase the number of extraction wells to prevent contamination from reaching the river or groundwater supplies. In addition, he instructed the Health Department to start taking weekly samples of river water.

Entergy and the state are locked in a dispute over Vermont Yankee’s operation. The state senate refused to grant the plant a certificate of public good to continue operating beyond March 2012. Entergy filed suit against the state in April, saying that the Nuclear Regulatory Commission has sole authority to grant an operating license for the plant. The case is expected to go to court in September and Entergy is moving ahead with a scheduled refueling outage.

The U.S. Nuclear Regulatory Commission granted Vermont Yankee a 20-year license extension in March 2011.

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