VERNON—The Vermont Department of Health announced on Aug. 17 that laboratory tests revealed low levels of the radioactive isotope tritium on the Connecticut River’s shoreline adjacent to the Vermont Yankee nuclear power station.
“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,” said Health Commissioner Harry Chen, M.D.
Although less than one-third the safety threshold set by the Environmental Protection Agency, the samples were “above the limited level of detection so we consider [the test results] real,” said Dr. William Irwin, DOH radiological health chief and deputy director for planning.
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.
Entergy has released a statement challenging the DOH’s results, saying that the plant’s independent testing of the same river water samples did not show detectable levels of the isotope.
Irwin said the DOH has “always described” the ground water at VY contaminated with the tritium leak as “moving slowly to the river.”
The tritium, a radioactive form of hydrogen that emerged in a sample taken from a VY test well in November 2009, has not shown up in any sources of drinking water off-site, said Irwin.
In January 2010, VY confirmed that tritiated water had leaked from underground pipes near the Advanced Off-Gas (AOG) Building. Later lab tests also revealed 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. Theses results could substantiate the theory that the leak at VY started in 2007, said Irwin.
The timeframe fits projections based on the distance from the first monitoring well showing tritiated water in 2009 to the leak’s source, said Irwin.
The department collected the river water from a testing point near the shoreline next to the plant in Vernon, an “ideal” location for “capturing the tritium as it moves” into the Connecticut, Irwin said.
The sample was split, with half taken by the health department for testing and the other half sent to a lab used by VY’s owner, Entergy.
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.
For the past 18 months this “sample port” has monitored the groundwater flowing into the river. The DOH collects samples from this port weekly, he said.
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.
Entergy issued a statement through VY spokesperson Larry Smith refuting 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,’” read the statement.
“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,” wrote Entergy.
“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,” the company wrote.
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 groundwater, said Smith.
Vermont Gov. Peter Shumlin issued a statement saying, “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.”
According to Shumlin’s statement, 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.
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, such as air and soil.
Earlier this month, the DOH reported finding the radioactive isotope strontium-90 in “edible portions” (the flesh) of fish captured nine miles upstream of VY [The Commons, Aug. 10].
Chen said the DOH had received laboratory results “confirming the accuracy of that finding” on Aug. 17.