Also see "Activists consider tank waste cleanup tradeoffs,"
 http://www.hanfordwatch.org/archive/activists_consider_tank_waste_cleanup_tradeoffs.htm
Tri-City Herald
April 1, 2005
http://www.tri-cityherald.com/tch/local/story/6331913p-6208400c.html
By Annette Cary, Herald staff writer
Hanford has emptied the nuclear waste from a second underground tank,
state and federal officials said Thursday.
It's an accomplishment not only because it means another of Hanford's
177 massive tanks is ready to be closed, but also because of the
amount of waste contractor CH2M Hill Hanford Group was able to
remove.
"They retrieved more than 99 percent, which is incredibly
impressive," said Sheryl Hutchison, spokeswoman for the Washington
State Department of Ecology.
As the United States raced to build an atomic bomb during World War
II, it built single-shell tanks intended for temporary storage of
radioactive and chemical waste left from the separation of plutonium
from irradiated fuel.
But 62 years after those first tanks were built, all but two still
hold waste. Of Hanford's 149 single-shell tanks, 67 may have leaked a
total of about 1 million gallons of radioactive waste into the
ground.
The newly emptied tank, Tank C-203, is listed as a potential leaker
because of an unexplained four-inch drop in its contents. The
radioactive waste it held had begun accumulating shortly after World
War II.
That's one of the reasons it was picked to demonstrate a retrieval
method that looked promising for tanks that Hanford officials fear
might leak if more liquid is added.
Last year, the last of the liquid contents were emptied from all the
single-shell tanks, but the tough job of removing sludge or hardened
salt cake at their bottoms remained.
On the first tank to be emptied of solids, Tank C-106, Hanford
workers used a sluicing method that involved adding acid to dissolve
sludge and then using water to wash away the waste.
For Tank C-203, workers used a vacuum with a hose inserted within the
closed tank to suck up a sludge that contained cesium and strontium.
A high-pressure spray of water was used sparingly to break up
stubborn clumps of waste that couldn't be sucked up otherwise.
The earlier removal of liquid waste had emptied the 55,000-gallon
tank of all but 3,075 gallons of waste, said Zack Smith, acting
assistant manager for the tank farms project for DOE's Office of
River Protection.
The Tri-Party Agreement, which regulates Hanford, required that no
more than about 240 gallons of waste could remain at the bottom of
the huge tank.
Workers were able to vacuum up all but 35 gallons on the bottom of
the tank and an estimated 50 gallons that clings to its walls, said
Roy Schepens, manager of DOE's Office of River Protection.
"This certainly meets and exceeds the TPA," or Tri-Party Agreement,
Hutchison said.
Contents were pumped into newer double shelled tanks to wait for
processing for permanent disposal. Much of the 53 million gallons of
tank waste is expected to be turned into a stable glass form at the
$5.8 billion vitrification plant under construction.
Fourteen months have passed since workers finished emptying the first
single shell tank.
Work at Tank C-203 was delayed in recent months because of equipment
failures. Work also has proceeded somewhat more slowly as CH2M Hill
instituted new procedures to protect workers from chemical vapors
that vent into the air from the single-shell tanks.
After demonstrating that vacuuming works well on some tank waste,
CH2M Hill is ready to use the technique again. It expects to start
vacuuming the remaining waste from the three other smaller tanks at
the C Tank Farm. They all were built with a 55,000-gallon capacity,
although some single-shell tanks could hold up to 1 million gallons.
Work also is progressing to empty two other tanks. Work to empty Tank
S-112 using a sluicing method is 95 percent complete, Smith said. All
that remains is a crust at the bottom the consistency of concrete.
Work at Tank S-102 has proved more difficult and is about 10 percent
complete.
The two empty tanks still need to be permanently closed. But that
work will wait until a policy decision is made with public input.
Among options that have been discussed is grouting the residual waste
in place and then filling the rest of the tank with grout to keep it
from collapsing.
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