Hanford begins waste retrieval
By Annette Cary, Herald staff writer
HANFORD — Hanford workers began retrieving radioactive and hazardous chemical waste from Tank C-110 this week.
They’re hoping it marks the first sustained effort to retrieve solid waste from leak-prone underground tanks since late July 2007 when a spill of waste stopped operations.
It also ends CH2M Hill Hanford Group’s efforts at the tank farms on a positive note. New contractor Washington River Protection Solutions takes over operations of Hanford’s tank farms Oct. 1 under a $7.1 billion contract.
CH2M Hill has completed removing waste from seven Hanford tanks and has done some work to retrieve solid wastes from four more, including Tank C-110. It also removed pumpable liquid from all 149 of Hanford’s leak-prone single shell tanks.
Waste left from the past production of plutonium for the nation’s nuclear weapons programs is being pumped from single-shell tanks into 28 sturdier double shell tanks to await treatment and disposal.
“Removing the waste from these single shell tanks is a priority for (the Department of Energy), a necessary step to protect the nearby Columbia River and prepare for future operations at Hanford’s vitrification plant,” said Stacy Charboneau, DOE assistant manager for tank farms, in a statement. The vitrification plant will turn much of the tank waste into a stable glass form for disposal.
The past year has been difficult for CH2M Hill after a spill in July 2007 stopped waste retrieval until early this summer.
Then retrieval resumed on Tank C-109, but had to stop after several weeks because of a mechanical problem with a promising new type of robot.
However, CH2M Hill Hanford Group believes it can use proven technology to retrieve waste from Tank C-110.
While Tank C-109 had a hard heel of waste left in its bottom that was difficult to break up, Tank C-110 has sludge in its bottom that should be less difficult to maneuver and pump out.
It is using modified sluicing, a technology that uses a nozzle to spray the waste inside the enclosed, underground tank with liquid to break it up and move it toward a pump for removal from the tank.
The tank, built in 1946, has 177,000 gallons of sludge and other waste materials at its bottom. Earlier, pumpable liquids were removed from the 530,000-gallon tank.
It is on the list of tanks suspected of having leaked in the past, and modified sluicing typically isn’t the preferred option for those tanks because it adds more liquid to the tank. But at Tank C-110 there are doubts that it really has leaked in the past, and if it did, the leak likely occurred in a portion of the tank above the current waste level.
Rather than using clean water for the sluicing, liquid waste will be used as a spray to reduce the amount of new waste produced in the retrieval operation.
Workers spent three months preparing to start retrieval of Tank C-110, making improvements based on lessons learned from last year’s spill at Tank S-102.
CH2M Hill has installed improved methods to detect any leaks in the 900-foot transfer line between the single-shell and double-shell tanks. The waste is transferred in a temporary above-ground line that includes a hose encased in another hose.
Five new cameras for remote monitoring have been installed. They’re equipped with a high quality zoom, a pan and tilt system and a high intensity spotlight that can be operated by workers at a safe distance to check for visual evidence of potential leaks.
In addition, radiation monitors have been set up at 10 locations along the transfer route. The radiation monitors sound an alarm if abnormal radiation levels are detected, limiting the need for workers to enter areas regularly that could pose a risk.
“Everything we do is focused on worker safety and protection of the environment and this job is no exception,” said Ryan Dodd, CH2M Hill vice president for retrieval and closure operations, in a statement.
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