Test results from a drinking water well at Vermont Yankee show samples are clean and the nuclear power plant’s response to the discovery in January 2010 of a leak is officially over, said a Yankee spokesman.
“As far as we are concerned, this is the end,” said Jim Sinclair, manager of communications.
On Sept. 17, Yankee technicians sampled a decommissioned drinking water well connected to the plant’s construction office building (COB). Samples ended up analyzed by the Vermont Department of Health (DOH) and a laboratory contracted by Yankee.
“Test results from both the Health Department Laboratory and its contract laboratory report that neither tritium nor gamma-emitting radioactive materials were detected in the COB well samples,” said a release from the DOH. “Tritium results … were all less than the detection limit for all three samples.”
The detection limits reported were between 511-530 picocuries per liter for tritium.
DOH is in the process of testing for hard-to-detect radionuclides such as iron-55, nickel-63 and strontium-90.
“We should get those in the next few weeks,” said Bill Irwin, radiological health chief for DOH.
On Jan. 7, 2010, Yankee representatives notified DOH that a sample taken from a ground water monitoring well contained tritium. The finding signaled an unintended release of radioactive material.
Officials found the source of the leak a little more than a month later, but not before samples revealed contamination at more than 500,000 picocuries per liter.
The EPA standard for drinking water is no more than 20,000 picocuries. Officials never found tritium in drinking water wells either on or offsite.
Entergy, which owns and operates Yankee, mitigated the leak by withdrawing contaminated water from the ground and cleaning it up before putting it back into the plant’s cooling system. Some of the contaminants ended up shipped off site to a disposal facility.
In October 2010, researchers found tritium contamination in the COB water well, a little more than 1,000 picocuries at 200 feet deep. At 300 feet there was no tritium above detectable level. Plant officials took the well out of service in March 2010.
In August 2011, tritium levels just above the lowest limits of detection were in the Connecticut River, which was consistent with hydrogeological modeling that showed the contaminated plume flowing toward the river.
In April 2011, the state and Entergy started talking about whether the COB well should undergo testing once more.
“We’ve always wanted to get these sample results because we hoped it would be verification that well water in the bedrock was protected,” Irwin said.
“Vermont Yankee attempted to sample the well in September 2010 during a procedure called packer testing, but stopped when tritium was found in the well. They tried again in February 2011, but stopped when pumping appeared likely to draw water down from the tritium-contaminated groundwater above the bedrock,” stated an update posted on DOH’s website in April 2011. “Yankee officials have concluded that sampling the COB well cannot be done without risking contamination.”
Entergy relented after receiving pressure from both the state and the Nuclear Regulatory Commission (NRC).
“We urged the company to check the COB well — as did the state — to check for any contamination at this lower elevation, and the company ultimately agreed to do so,” said Neil Sheehan, spokesman for the NRC.
The most recent results are what Entergy expected, Sinclair said.