|published Wednesday, July 06, 2011 ||776 Views :: 0 Comments |
July 05, 2011
By Annette Cary
From the Tri-City Herald
The federalgovernment is asking for the public's opinion as it decides how muchof the soil contaminated by plutonium and other radionuclides andchemicals in the heart of Hanford should be dug up.
TheDepartment of Energy with the Environmental Protection Agency ispreparing to make one of the first decisions about environmentalcleanup in the approximately 10 square miles of central Hanford,where permanent disposal of radioactive waste is planned.
Unlikethe remainder of Hanford, the 10 square miles called the CentralPlateau Inner Area is being cleaned up only to industrial standardswith the plan that no one will ever live there.
The areaincludes massive lined landfills for low-level radioactive andchemical waste, and also for low activity waste that will be turnedinto a stable glass form at the vitrification plant.
Itincludes U Canyon, a processing plant longer than the space needle istall, where rubble will be covered with a massive cap. It's also hometo the 177 tanks used to store 56 million gallons of radioactivewaste.
DOE is expected to grout in those tanks and leave themin the ground when as much as possible of the waste is removed.
Nowthe federal government is deciding how much of the contaminated soilnear those sites should be dug up and disposed of either in a nearbylandfill or a national repository. The soil was contaminated whenwater tainted with plutonium, plus other radionuclides and chemicals,was discharged into the ground there.
Initially, DOE wasconsidering leaving the four contaminated soil sites and coveringthem with an earthen cap that would be engineered to keepprecipitation from driving contamination deeper toward the groundwater. That would be supplemented with a current vapor extractionsystem to clean up carbon tetrachloride in the soil and a system topump up and treat contaminated ground water.
But that wasbefore hearing from the Hanford Advisory Board, state of Oregon andthe tribes during initial discussions in 2008.
Concerns wereraised about leaving plutonium in particular in place because of itslong half life, a measure of how long it takes for half theradioactivity to decay. Plutonium 239 has a half life of 24,000years.
"We looked at it and saw benefits to removal,"said Nick Ceto, DOE record of decision program manager until hisretirement last week.
"The question is how much to digup," said Emerald Laija, Environmental Protection Agencyscientist.
Plutonium typically clings to the soil rather thaneasily spreading deeper. But some of the plutonium is mixed withnitric acid that can cause it to travel deep into the soil, possibly100 feet underground.
Some of the excavated soil likely wouldbe contaminated enough to be sent to the Waste Isolation Pilot Plantin New Mexico, the nation's repository for transuranic waste,including waste contaminated with plutonium. Other waste could beclassified as low level radioactive and chemical waste and disposedof at the Environmental Restoration Disposal Facility, or ERDF,nearby.
That includes soil contaminated from cooling water andsteam condensate from the Plutonium Finishing Plant complex, whereplutonium was shaped into metal buttons the size of hockey pucks forthe nation's nuclear weapons program.
The cooling water wassent through a series of shallow open ditches from 1944-95 to a pond.When one ditch would become too contaminated, another one would bedug alongside it. The trenches were about four to six feet deep,although the system includes a deeper tile field.
DOE isproposing the contaminated soil be dug up and likely sent to ERDF.Cost is estimated at $58 million.
The remaining three soilwaste sites were all used for disposing of processing waste water,including from the Plutonium and Uranium Extraction facility, orPUREX, which was used to extract plutonium from irradiated fuelrods.
For the plutonium contamination there not mixed withnitric acid, DOE is proposing digging down as much as 33 feet toremove a significant portion of the contamination. It likely would betaken to New Mexico. An earthen cap to prevent infiltration of waterwould be constructed over the top. Cost would be $81 million.
Forareas with plutonium mixed with nitric acid, DOE is proposing diggingdown deep enough to get to the disposal structures and then coveringthe excavated site with about 22 feet of clean soil and a cap. Costwould be about $107 million.
An area with primarily cesium137, which has a half life of 30 years, would not be dug up, but soilwould be added to make sure contamination is covered by at least 15feet of clean soil. Cost would be $11 million.
In addition,some settling tanks would have sludge and liquid containing plutoniumand americium removed and sent to the national repository. The tankswould be grouted in place for a project cost of $40 million. Anadditional $5 million would be spent to excavate pipelines.
Afinal decision about cleanup is expected by Sept. 30.
Publiccomment will be heard at a meeting from 6:30 to 8:30 p.m. July 19 atthe Richland Public Library Gallery, 955 Northgate Drive, Richland.An open house will be held starting at 5:30 p.m. Public meetings alsoare planned in Seattle, Portland and Hood River, Oregon.
Theproposed plan is posted at www.hanford.govunder the public calendar on each day through Aug. 5, the end of thepublic comment period.
Public comment also can be sent toPW136PP@rl.gov orto Paula Call, DOE Richland Operations Office, P.O. Box 550, A7-75,Richland, WA 99352.
IF YOU GO
Publicmeeting on central Hanford waste sites
WHEN: 6:30 to 8:30 p.m.July 19, with an open house at 5:30 p.m.
WHERE: RichlandPublic Library Gallery, 955 Northgate Drive.
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