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.

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

10 thoughts on “Tracking the Source: Pilgrim’s Tritium Link”

  1. BWR plants have safety valves located in the steam lines, above the reactor. These valves will manually or automatically open to depressurize the reactor to release steam, and will fully depressurize the reactor under certain conditions (Low water level 1 alarm + low pressure injection systems available). I am talking about the steam IN the reactor steam dome, NOT the containment.

  2. The above post demonstrates the preparedness of government departments plus the fore thought place into emergency situations

  3. Since the beginning of groundwater monitoring at the Pilgrim nuclear power plant in November 2007, tritium concentrations to date have fluctuated but have shown a declining trend. The highest concentration of tritium identified so far was 25,552 picocuries per liter. That level was found in Monitoring Well 205 on July 7, 2010. To put that in perspective, the EPA limit for tritium in drinking water is 20,000 picocuries per liter. However, the groundwater at Pilgrim is not used for drinking purposes.

    Currently, all of the monitoring wells are showing low concentrations. The most recent well samples indicated concentrations that are below what is considered by the NRC to be the lower limit of detectability, which is 2,000 picocuries per liter for tritium. (Concentrations below the lower limit of detectability can be measured, but the levels are so low they are difficult to count and are not considered harmful to worker and public health and safety.) For the month of April, concentrations ranged from 354 to 1,960 picocuries per liter. As an example, Monitoring Well 205 on April 18th had a concentration of 354 picocuries per liter.

    With respect to the 4-inch underground pipe found to have a break, discharges from that line occurred from March 6 to 26, 2013. Groundwater migration rates are typically slow (perhaps as slow as 6 inches per month) and therefore efforts to determine if the line is, in fact, the source of the tritium contamination will likely take some time.

    The NRC has devoted considerable time and resources over the years on studying the best ways to prevent groundwater contamination at U.S. nuclear power plants. More information regarding those reviews, including the Commission’s open and transparent deliberations in this area, can be found on the agency’s web site at:

    Neil Sheehan
    Public Affairs Officer, Region I

  4. Looking at the 2013 results.
    The EPA limit, (which by many accounts is extremely overconservative), is 20000 pCi//L at the drinking tap. The measurements in these wells, (which is far away from the tap), is well below even the EPA limit. Even a measurement >20000 pCi/L at a well does not immediately mean drinking tap water is greater than the EPA limit, as the ground as well as water supplies that the tritiated water reaches will further dilute this.

    I agree the leaks should be identified and fixed as it is an unmonitored/uncontrolled release path, but ultimately there is no public health and safety concern with the levels that are being recorded. The NRC’s limits for public radiation exposure are far above the EPA limit. I don’t know the basis for where EPA set the limit , but the NRC looks at the general risks of radiation exposure to the public, and sets a general limit of 100 mR/year per 10CFR20. 20000 pCi/L results in a few mR/year (I’m thinking <5, there are some assumptions about the amount of water that is consumed….one would have to go to the EPA site to see that).

  5. The Massachusetts Department of Public Health’s Radiation Control department, Environmental Monitoring link has all test results and location monitors - – hope this answers your request.

  6. Please provide some detail. What is the concentration of tritium that you are finding and concerned about in this article?

  7. Pilgrim Watch response to (4) statements in press release:
    “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”
    The efforts got underway due to: (a) the rash of leaks at reactors around the country, including Pilgrim and Vermont Yankee that spurred the Governor of Massachusetts to contact NRC saying that neither reactor should be relicensed until the sources of leaks were identified and directed the Massachusetts Department of Public health to take split samples at Pilgrim and track the status of monitoring; and (b) a contention in Pilgrim’s license renewal adjudication process regarding leaks of radioactive material from buried components at Pilgrim.
    The detected levels of tritium were persistent and above the standards set by California, Colorado and Canada, for example.
    “There is still more checking to be done, but now there is a possibility a 4-inch underground pipe might be the culprit.” Yes there is more checking to be done because it is likely that other buried pipes and tanks are or are about to leak because: Pilgrim’s buried components are old (corrosion is a function of age); they are buried in a corrosive environment (corrosion results from exposure to moisture and salt); and the aging management program is insufficent.

    “It’s important to note that the tritium contamination has remained on-site.” Neither NRC nor the public knows what has or has not leaked offsite. Because until 2007, there were no monitoring wells onsite and at that time only four were installed- the number required at a typical corner service station. The number of wells at Pilgrim remains inadequate in number and there is uncertainty if all are placed according to potential sources and hydro-geological conditions at the reactor site.

    “Voluntary industry initiative:” After the leaks at Braidwood and the proliferation of leaks around the country, NRC established a Task Force. The Task Force recommendations were impressive; however NRC chose once again not to regulate but allow the industry to put into place voluntary measures that does not serve the public interest and is an abrogation of NRC’s mandate to protect public health and safety and enforce its own rules that prohibit unmonitored radiation materials to go offsite unmonitored.

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