VERNON — After a long deliberation, federal regulators have approved a proposal to ship 200,000 gallons of contaminated water from Vermont Yankee to a disposal site in Idaho.
The water is from plant operations and contains “low concentrations” of radioactivity, officials said.
But the federal Nuclear Regulatory Commission had taken time to mull over several questions, including the extent to which truck drivers would be exposed to radioactivity as they hauled the water cross-country.
“In the end, we were provided with satisfactory answers,” NRC spokesman Neil Sheehan said.
Vermont Yankee administrators are dealing with two kinds of contaminated liquid - “intrusion water” is groundwater that has been seeping into the plant's turbine building, while “process” water is leftover from plant operations.
Intrusion water has been getting the most attention, as Entergy has been working to plug leaks while also sending tanker trucks of the wastewater to a disposal site in Tennessee.
Joe Lynch, senior government affairs manager for plant owner Entergy, told a recent meeting of the Vermont Nuclear Decommissioning Citizens Advisory Panel that administrators are “still looking at opportunities to seal leakages in the lower part of the turbine building.”
Lynch said about 650 to 675 gallons of water are entering the building daily. That's an improvement from rates that reached a few thousand gallons a day early last year, when the problem was at its worst.
“It's showing that the efforts that we've made over the past year or so have [resulted in] a significant reduction in the intrusion rate,” Lynch said.
The Idaho proposal, on the other hand, has to do with process water that's stored in a large reservoir called the torus. That tank includes water that has been drained from the plant's reactor pressure vessel.
The torus is large - it can hold up to 1.1 million gallons - and Entergy saw US Ecology's facility near Grand View, Idaho, as an important backup disposal option for Vermont Yankee water.
That plan required federal action on two fronts. Entergy needed permission to pursue an “alternate disposal” plan, while US Ecology needed a regulatory exemption since it doesn't have an NRC license.
The NRC granted both of those requests in letters issued to each company on June 20.
Federal regulators, who last year asked Entergy for more information on the water's radioactivity, now have determined that expected radiation doses to truck drivers and US Ecology workers won't add up to more than “a few millirem per year.”
The millirem, equal to one-thousandth of a rem, is a unit used to calculate radiation doses. For context, Sheehan said, “the average American is exposed to about 620 millirems of radiation each year from natural and manmade sources.”
The NRC also found that Entergy “has provided an adequate description of the waste to be disposed of and the proposed manner and conditions of waste disposal.” The water would be “solidified with clay” before disposal at US Ecology, documents show.
Furthermore, Entergy has “committed to performing a representative sample prior to each shipment of water” to confirm levels of radioactivity, the NRC says.
Entergy and US Ecology submitted their regulatory requests in January 2016. It took until this spring for the NRC to issue an environmental determination on the matter, and more than 17 months passed before the commission OK'd the proposal.
But Sheehan said that isn't necessarily an unusual schedule.
“Our evaluations for license amendment requests typically take about a year,” he said. “This request also had some unique elements to it, including the [US Ecology] waiver issue and the need for calculations on the dose levels the truck drivers hauling the material to Idaho would receive.”