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The Vermont Department of Health announced Wednesday evening that detectable levels of the radioactive isotope tritium had been found in samples taken from the Connecticut River near the Vermont Yankee nuclear power station.

The department confirmed that samples of water from July 18 and July 25 contained very low levels of tritium. The samples measured 534 picocuries per liter and 611 picocuries per liter, just above the lower limit of detection. The water was taken from the river at the point where contaminated groundwater flows from the shoreline.

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Dr. Harry Chen, commissioner of the Health Department, said the state has been monitoring river water at the same location on a weekly basis for months.

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

Leaks of tritiated water, or water contaminated with radioactive hydrogen, were discovered in January 2010. The revelation was made about seven months after Entergy Corp. officials told the state that Vermont Yankee did not have any underground pipes on the facility compound. The piping system is original to the nuclear reactor, which was built in 1972.

Entergy officials scrambled to find the source of the leak, and pinpointed pipes located underground in concrete tunnels under the soil. They removed the soil around the site and installed four pumps to remove water from the ground around the contaminated area to prevent the radioactive material from moving toward the river. Entergy had planned to shut off the pumps, but after a standoff with Gov. Peter Shumlin, company officials agreed to keep two running through the winter. Those pumps are still operating, though they have removed very little additional liquid from the site.

Two weeks ago, the department announced that nine fish tested for radioactive contamination had detectable levels of strontium-90 in their bones. One of the fish, a bass, had trace amounts of SR-90, a highly radioactive substance, in its flesh.

Entergy has released a statement challenging the water sample results the department issued on Wednesday. Officials say the river water samples tested by the company’s lab did not contain the isotope. Entergy and the department “split” samples and send them to different laboratories for testing.

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Larry Smith, communications director for the plant, said Entergy, which tests river water samples on a weekly basis, has offered to send state and company samples to an “independent third party laboratory for an additional round of testing.”

Although the tritium levels were low, Dr. William Irwin, Department of Health radiological health chief, said the water samples were “above the limited level of detection, so we consider them [the test results] real.”

Irwin said the department has “always described” the contaminated ground water at Vermont Yankee from the tritium leak — tests first revealed in November 2009 — as “moving slowly to the river.”

The tritium has not been found in any sources of drinking water off-site, said Irwin.

In January 2010, Vermont Yankee confirmed that tritiated water had leaked from underground pipes near the Advanced Off-Gas (AOG) Building. Later lab tests also identified radioactive isotopes strontium-90, cesium-137, and cobalt-60 in the soils surrounding the leak.

The Connecticut River test samples represent the first instance of tritium reaching the river. These results could substantiate the theory that the leak at VY started in 2007, said Irwin.

The timeframe fits, explained Irwin, based on the distance from the first monitoring well showing tritiated water in 2009 to the leak’s source.

According to Irwin, the Health Department’s tests showed levels slightly above the lower level of the lab instruments’ detection ability of 500 picocuries per liter. The first sample collected July 18 measured 611 pCi/L, and the second collected July 25 measured 534 pCi/L.

The federal Environmental Protection Agency’s acceptable limit for drinking water is 20,000 pCi/L, said Irwin.

The hydrogeology of the VY site, like most nuclear plants near water, drains toward the river, said Irwin. The groundwater closest to the Connecticut “communicates” by rising and falling to similar levels as it flows from the soil to the river.

According to Irwin, the department collected the tritiated samples from a hose in the river located about four-feet under the water. That, Irwin said, is an “ideal” location for “capturing the tritium as it moves” into the Connecticut.

For the past 18 months, this “sample port” has monitored the groundwater flowing into the river. The department collects samples from this port weekly, he said.

When asked if the tritium posed a danger to the public, Irwin answered: “No. Absolutely not.”

As it enters the Connecticut, the tritiated groundwater “rapidly mixes” with the river water and dilutes, he said.

Tritium levels at the DOH’s approximately six sampling sites upstream and downstream of VY remain “undetectable,” said Irwin.

According to Irwin, the DOH is considering sampling the water around VY more frequently to gather additional data.

“The more samples you get, the better conclusions you can draw,” he said adding the department will continue testing other areas of the environment for radioactive contamination like air and soil.

Entergy issued a statement through VY spokesperson Larry Smith disputing the DOH’s findings. “Results from our laboratory testing of those same samples, however, show levels that are below that same extreme lower limit, otherwise known as below ‘minimum detectable,” Smith wrote.

“While it is important to note that the levels detected are extremely low, and there is no risk to the environment or public health and safety, we are very interested in working with the State to understand the discrepancy in the test results,” Smith said. “As such, we have proposed to the State that we send both our samples and theirs to an independent third party laboratory for an additional round of testing.”

According to the statement, the company has expedited three weeks of test results from its laboratory and continues to pump groundwater from around the AOG leak.

To date, VY has extracted 334,900 gallons of contaminated groundwater, said Smith. The company pumped 300,000 gallons of liquid from the ground in December.

What groundwater VY did not extract from the soils surrounding the leak site “was going to end up in the river,” Irwin said.

So far, the tritium levels in the plant’s 31 monitoring wells have followed a pattern of peaking, then declining, said Irwin.

The July river levels will likely follow the same pattern as the tritium “makes its final exit from the land within the next year or so,” he said.

Neil Sheehan, communications director for Region 1 of the Nuclear Regulatory Commission, said even if all of the tritium in the groundwater now on the site leached through soil into the river, the river contamination would be far below dangerous levels of exposure for children.

Sheehan said the total amount of release would be approximately 2.79 curies, he said.

“A tritium exit sign has up to 25 curies of tritium,” Sheehan said.

The maximum exposure from the release would be about 0.00026 milirems in one year for an individual child. The annual average exposure to manmade and natural sources of radiation is about 620 millirems, he said.

Sheehan attributed the detectable tritium readings to low river levels this time of year.

“Even if it does turn out to be true, the center line of the plume is the most intense release point,” Sheehan said. He suggested that if the sample had been taken away from the shore, tritium would not be detected.

Gov. Peter Shumlin, who is named in Entergy’s lawsuit against the state and has been a vociferous critic of the company’s management of the plant, did not elaborate on the most recent findings at his press conference on Thursday. In a statement he said: “I am very concerned about the latest findings from the Vermont Health Department. Confirmation that tritium has reached the shoreline of the Connecticut River is further evidence of the immediate need for more extraction wells and increased monitoring of the situation.”

The governor wrote plant officials on Aug. 3 calling for an increase in the number of extraction wells to prevent contamination from the nuclear facility from reaching the river or groundwater supplies. He also instructed the DOH to obtain weekly water samples from the Connecticut River at the shoreline and other locations in the river.

Earlier this month, the DOH reported finding the radioactive isotope strontium-90 in “edible portions” (the flesh) of fish captured on June 9 nine miles upstream of VY. Chen said the DOH had received laboratory results “confirming the accuracy of that finding” on Aug. 17.

Editor’s note: Anne Galloway contributed to this report.

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