A nuclear error: Tritium, Maine Yankee, and Vermont

Posted Wednesday, June 22, 2011 in Investigation

A nuclear error: Tritium, Maine Yankee, and Vermont

Spent nuclear casks at Maine Yankee, photo by Raye Tibbitts

by Gina Hamilton

According to recent investigative reporting by the Associated Press and published by the Bangor Daily News (among other newspapers), 75 percent of all nuclear power plants in the United States have released radioactive tritium at some point.

Tritium is an isotope of hydrogen that contains a proton and two neutrons (normal hydrogen contains a proton and no neutrons). It is very rare in nature – virtually all tritium arises due to nuclear processes of some sort, and tritium was (and is) the trigger for nuclear weapons. 

Tritium decays rather quickly into helium, but it poses a threat to human health before it decays, especially if the tritium is in drinking water. And most of the known leaks, according to the AP report, have involved tritium in water supplies of one sort or another.

Tritium has leaked from at least 48 of 65 sites, according to U.S. Nuclear Regulatory Commission records reviewed as part of the yearlong examination of safety issues at aging nuclear power plants. Leaks from at least 37 of those facilities contained concentrations exceeding the federal drinking water standard – sometimes at hundreds of times the limit.

Although none of the leaks is known to have contaminated public water supplies, several private wells have been impacted in Illinois and in Minnesota ... and, as we now know, near Maine Yankee. In New Jersey, tritium has entered the water system of the Barnegat Bay and has entered the Atlantic Ocean.

In 2009, Patrick Dostie, state nuclear safety inspector for the state of Maine, did testing of wells at Maine Yankee. This is part of what he wrote in his May report:

On May 12th the State received Maine Yankee's results from the September 2008 and March 2009 sampling events. Maine Yankee's results for September 2008 identified three wells with positive indications of Tritium, a natural radioactive form of Hydrogen (H-3)4. Two of three wells had background Tritium levels ranging from 410 to 450 pCi/L5 with the highest well at 38,720 pCi/L. In comparison Maine Yankee's Tritium results for March 2009 were comparable to those in September with the same three wells having positive indications. Two wells were found to have low levels of Tritium ranging from 370 to 440 pCi/L. The high Tritium well had a concentration of 36,480 pCi/L.

Any exposure can cause cancer. The U.S. Environmental Protection Agency says tritium should measure no more than 20,000 picocuries per liter in drinking water. The agency estimates seven of 200,000 people who drink such water for decades would develop cancer. The "high Tritium well" at Maine Yankee, two years ago, had a rate of tritium nearly twice the EPA limit.

Now, the well is not being used for drinking water, and there is no evidence that the contamination has extended beyond Maine Yankee's borders, but tritium leaks caused severe heartburn for Vermont Yankee's owner, Entergy, when that state voted to shut down the Windham County plant.

In 2010, the Vermont Senate, seriously concerned about the tritium leaks there (at more than 100 times the EPA drinking-water standard), voted to block relicensing of the aging facility at the end of its current license in March of 2012. The state Legislature has the power to block nuclear power licensing in Vermont.

However, over the state's objections, the Nuclear Regulatory Commission gave Vermont Yankee a 20-year license extension. Entergy sued Vermont in federal court, challenging the state's right to shut it down.

Vermont Yankee has been troubled by inadequate maintenance for years. In 2007, part of a cooling tower collapsed there, and for two years, the plant operated at 50 percent capacity. The collapse triggered an investigation of the plant's reliability and safety.

Entergy didn't help its cause by "miscommunicating" facts about the corrosion of pipes that were found to contain water laced with tritium during those years. In January 2010, tritium was found in test wells at rates 37 times the allowable amount; the next month, the amounts were 125 times the drinking-water limit.

The source of the leak is not yet known, but in the search, other contaminants were found. Levels of cesium-137 were found to be three to 10 times higher than background levels. Silt in a pipe tunnel contained 2,600 picocuries/kg, but contamination outside the pipe tunnel was limited to a small volume, about 150 cubic feet (4.2 m3) of soil. No one is sure of the cesium origin, either. It could represent a nuclear fuel leak, or it might have originated from problems with fuel rods before 2001. The amount of cesium detected is small and in these quantities is thought to be harmless, but that they were undetected for such an extensive period of time concerns the Vermont radiological health chief, Bill Irwin.

Entergy has the plant up for sale, but in the uncertain legal climate, it is unlikely to find a buyer.

Although the NRC has granted a conditional 20-year extension, that will depend on Vermont Yankee prevailing in its lawsuit against the state. If it loses in court, Vermont Yankee will close in March of 2012.

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