Vermont Yankee nuclear plant continues monitoring groundwater for tritium
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The Vermont Yankee nuclear power plant continues to monitor groundwater for tritium after the radioactive isotope was discovered in high amounts in a test well on its property near the Connecticut River last year.
The leak was followed by a series of other positive readings for tritium and other radioactive substances on the plant's grounds. The most recent tritium leak was reported in a test well in January and its source is not definitely known, though the plant took a discharge line out of service as a result.
"They haven't fully been able to demonstrate cause and effect," said Neil Sheehan, a spokesman for the U.S. Nuclear Regulatory Commission.
Representatives at the plant in Vernon, Vt., say they suspect the tritium found in January is from a plume linked to tritium discovered a year earlier in groundwater at the plant, but they can't say for sure. The tritium readings at this well are now non-detectable, according to the NRC.
"We think it might just have been groundwater flowing from the first leak," Larry Smith, spokesman for Vermont Yankee, said Monday.
Plant officials and federal regulators say the underground tritium so far poses no threat to public health, but it prompted an investigation by the NRC and backlash from Vermont lawmakers, who last year sought to thwart the 20-year license renewal that plant owner Entergy was seeking.
The Vermont Senate was so troubled by tritium leaks - as high as 2.5 million picocuries per liter at the reactor, or 125 times the EPA drinking-water standard - that it voted to block relicensing. The Senate vote also followed admissions by the plant that it misled Vermont regulators and lawmakers about whether the plant had the kind of underground piping that carries radioactive material.
In March, the NRC granted the plant its 20-year license extension, despite state opposition. Weeks ago, Entergy sued Vermont in federal court, challenging its authority to force the plant to close. The plant's permit expires in March 2012.
Tritium is a radioactive isotope of hydrogen and a product of nuclear fission. It is a carcinogen when ingested, inhaled or absorbed in large amounts.
Monitoring work
The discovery last year of tritium prompted the nuclear plant to monitor drinking water wells on and off site and the Connecticut River. Workers dug 32 monitoring wells around the plant, and the company continues to take regular readings, which are reported to Vermont state agencies and the NRC.
In October 2010, tritium that had leaked from the plant turned up for the first time in a former drinking-water well tied to a deep underground aquifer. A month later, the plant shut down after workers detected radioactive material leaking from a pipe, which federal regulators said would have contained low levels of radioactive material such as tritium and other isotopes. The NRC oversaw the temporary shutdown.
In December 2010, more radioactive tritium was found in two test wells at the plant, including one near a former drinking-water well. Plant officials said the radioactive material was within the plume of tritium discovered earlier in the year.
Within the past year, Smith said, the nuclear plant has pumped and removed 325,000 gallons of tritium-contaminated water from the ground. As part of its remediation work, it also has recently completed a conceptual groundwater flow model to be turned over to state and federal regulators.
"It's something we had to do as part of the investigation," Smith said. "It helped to understand the hydrology of where the groundwater at Vermont Yankee is flowing, the quantities and makeup of the soils."
Dan Crowley can be reached at dcrowley@gazettenet.com. Material from the Associated Press was included in this story.
