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 health or safety, said the Nuclear Regulatory Commission.

David Tarantino, Pilgrim spokesman, said that a 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,’’ he 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 ground water 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 immediately 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 that careful monitoring was ongoing of the wells onsite, as well as in offsite places, such as the ocean, to ensure that contaminated water is not leaving the property.

Pilgrim is seeking a 20-year license renewal. Sheehan said 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.

Carolyn Y. Johnson can be reached at cjohnson@globe.com.

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