A monitoring well located on the ocean side of the Pilgrim Nuclear Station in Plymouth has registered elevated levels of the radioactive isotope tritium.
The tritium detected was still well below the Environmental Protection Agency's maximum allowable level in drinking water, and does not pose a risk to human health or safety, according to the Nuclear Regulatory Commission.
Pilgrim spokesman David Tarantino said that a multidisciplinary team of environmental engineers, chemists, maintenance and operations specialists, and others are now trying to pinpoint the source of the tritium.
"It's in an area where there's lots of underground systems that carry radioactive water, but we can't even say for certain that it's a leaking system yet," Tarantino said. Another source of tritium contamination occurs during "washout," he said, when tritium leaves the plant in water vapor and returns to the ground in rain.
Pilgrim has 12 monitoring wells as part of a groundwater protection initiative that the nuclear industry started after several high-profile cases of tritium leakage at the Indian Point nuclear plant in New York and the Braidwood nuclear power plant in Illinois. Earlier this year, a leak was discovered at Vermont Yankee in Vernon, Vt.
Neil Sheehan, a spokesman for the NRC, said that the problem at Vermont Yankee was more significant than the one at Pilgrim appears to be.
"These are fairly low levels here," Sheehan said. "The concern for us is whenever they see evidence for tritium above these low threshold limits, they imediately begin a process of trying to identify the source."
Tarantino said that water samples were also being provided to the state Department of Public Health, and careful monitoring was ongoing of the wells on-site, as well as in off-site places, such as the ocean, to ensure that contaminated water was not leaving the property.
Mary Lampert, director of Pilgrim Watch, expressed concern that there are not enough monitoring wells, and that the EPA standard for allowable tritium are outdated.
Pilgrim is in the midst of seeking a 20-year license renewal. Sheehan said that it was possible, but not likely, that the discovery of elevated tritium levels would play a role in whether the plant receives approval.
Ralph Andersen, senior director of radiation, safety, and environmental protection at the Nuclear Energy Institute, a trade organization for the nuclear industry, said that the detection of the tritium was evidence the system was working.
"Finding things at those low levels allows them to find where it's coming from, before it becomes a significant problem," Andersen said.
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