Tritium could affect VY cleanup costs
BRATTLEBORO -- The possible remediation costs of contaminated groundwater at Vermont Yankee nuclear power plant in Vernon due to a leak of tritiated water is dependent on a number of conditions, said a spokesman for the Nuclear Regulatory Commission.
The tritium decay rate is just one of those factors, said Neil Sheehan. Tritium has a half-life of 12.3 years, which means it will have lost half of its radioactivity during that period of time.
Other factors include groundwater flows, whether pumping contaminated water out of the ground could actually spread the plume and calculations used to determine the maximum amount of radioactive exposure that members of the public could experience as a result of the contamination.
"Entergy is still developing that information," said Sheehan, adding the NRC will review any and all remediation plans once they are completed.
Entergy, which owns and operates the power plant, has indicated it plans to place Yankee into SAFSTOR for several decades following shutdown, whenever that occurs, he said.
SAFSTOR is an NRC-approved method of mothballing a plant until much of the radioactive contamination at a plant has decayed and to allow a decommissioning fund to grow to the level sufficient to pay for cleanup.
Entergy has applied to the Nuclear Regulatory Commission to extend the operating license of Yankee for another 20 years, from 2012 to 2032.
In 2008, Entergy told the NRC that it has estimated there is 135,000 cubic feet of contaminated soil that would have to be removed at Vermont Yankee during decommissioning, with an estimated cost of $76 per cubic foot.
The total cost for that remediation would be $10,260,000, in 2008 dollars.
The 2008 report did not specify where the contamination came from, said Sheehan.
"The cost reported for soil remediation is based upon a preliminary assessment of the potential for contamination in the soil around the plant, based upon historical evidence," stated the report. "A detailed site characterization was not performed. This allowance will be confirmed and/or modified based upon more detailed analyses to be performed in conjunction with the formulation of a license termination plan."
How the tritium leak might affect cleanup costs is not known at this point, said Sheehan.
"Because Entergy has not yet finished characterizing the extent of the contamination from the tritium leakage, it would be speculation at this point as to how much additional soil might have to be removed or what the price tag for that work might be," he said.
Under its regulations, the NRC requires remediation of residual radioactivity to a level that permits, in most cases, unrestricted release of the site, said Sheehan.
"Once contaminated plant systems and structures are removed, any residual radioactivity would have to be reduced to a level at which a member of the public living on the site 24 hours a day, 365 days a year, would receive a maximum of 25 millirems of radiation exposure," he said.
The average American is exposed to roughly 360 millirems of radiation from natural and manmade sources on an annual basis.
"Our decommissioning cost estimates are based on meeting these requirements."
Sheehan said the principle of ALARA -- As Low As Reasonably Achievable -- would also be taken into account.
"That means an effort would be made to drive those levels even lower," he said.
In addition, states can set a cleanup standard more restrictive than the NRC's, said Sheehan. In Vermont's case, that level is 20 millirems.
"State projections of decommissioning costs can also cover the price of returning the site to ‘greenfield' condition,' he said.
An example of greenfielding would be the removal of an administrative building or another structure that had nothing to do with the nuclear power production process, he said.
"That is why state decommissioning cost estimates are typically higher than those reviewed by the NRC," he said.
James Matteau, the executive director of the Windham Regional Council, cautioned that even though the half life of tritium is relatively short, it could take 50 to 100 years for it to totally dissipate from the site. Of course, he said, that's also dependent on how much of the contaminated water makes it to the Connecticut River and is washed downstream.
Matteau also said it's the regional commission's position that SAFSTOR is unacceptable. Instead, the WRC is calling for a "prompt" cleanup of the site, which would commence about five years after shutdown, which is enough time for the last of the spent fuel to cool off in the plant's spent fuel pool.
WRC is also concerned about what effect SAFSTOR would have on employment in the region.
"In SAFSTOR, the place gets mothballed, locked up and guarded for as much as 60 years," said Matteau. "That means the jobs in the region will go down to the absolute minimum for as long as 60 years."
In three generations, a whole new group of people will arrive to begin the decommissioning, he said, and that means institutional memory would be lost.
Prompt cleanup could also mean Entergy would have to include the costs of tritium remediation in its decommissioning cost estimates, said Matteau.
Bob Audette can be reached at firstname.lastname@example.org, or at 802-254-2311, ext. 273.
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