Tracking the Source: Pilgrim’s Tritium Link

Neil Sheehan
Public Affairs Officer, Region I

pilgIt may not be as daunting as searching for the proverbial needle in a haystack, but the process of trying to track down the source of tritium contamination at the Pilgrim nuclear power plant has been long and painstaking.

Since mid-2010, efforts have been under way to determine why certain groundwater monitoring wells at the Plymouth, Mass., site have detected very low levels of tritium, a naturally occurring radioactive form of hydrogen that is also a byproduct of nuclear power plant electricity production.

While tritium emits a weak form of radiation, does not travel very far in air and cannot penetrate the skin, the release of the radioactive material via an uncontrolled pathway is unacceptable to the NRC.

There is still more checking to be done, but now there is a possibility a 4-inch underground pipe might be the culprit.

The NRC, from the time the contamination was identified, has continued to press the plant’s owner, Entergy, to hunt for the point of origin so that further leakage could be prevented. Work done to find the source included extensive visual inspections of tanks, and piping and dye tests to track groundwater flows at the facility.

Until recently, those efforts did not bear fruit.

However, water leakage into the reactor building that occurred in mid-April helped plant personnel focus on the pipe in question. This pipe is used infrequently during any given year, to allow for the discharge of water containing small amounts of radioactivity, which limited the opportunities to detect this break. Still, this pipe was due to be checked as part of a voluntary nuclear industry initiative to inspect underground pipes and tanks that has been under way for several years and that all plants have undertaken.

The NRC will independently verify whether the pipe is, in fact, to blame for the contamination. In the meantime, the pipe has been removed from service to prevent any additional leakage. An NRC inspection of the plant’s implementation of the voluntary industry initiative is scheduled for September.

It’s important to note that the tritium contamination has remained on-site. Since the groundwater there is not used for drinking-water purposes, there is believed to be no risk to plant employees or the public as a result of the contamination.