HANFORD — Workers have removed the radioactive sludge from the settler tubes in Hanford's K West Basin.
It's another step that will allow the radioactive sludge stored underwater at the K West Basin eventually to be moved farther from the Columbia River and treated for disposal.
Earlier Hanford workers consolidated all of the radioactive sludge in the K East and K West reactor basins in the K West Basin, which is sturdier.
Most of the approximately 37 cubic yards of sludge is held in five underwater containers. They hold sludge that was vacuumed from the floors of the K East Basin, which has since been drained and demolished, and the K West Basin, where all the sludge has been consolidated.
But the K West Basin also holds sludge in equipment that was used to wash fuel stored underwater at the K West Basin before the fuel was removed for dry storage. That includes about 4.6 cubic yards of sludge that were in settler tubes, which were part of the fuel washing system.
After the Cold War ended and Hanford stopped processing fuel to remove plutonium, 2,300 tons of irradiated fuel were left stranded at the K Basins, 400 yards from the Columbia River. The fuel corroded and contributed to the radioactive sludge that collected in the pools from dirt, sand and concrete that sloughed off the walls of the basin.
The last of the fuel was removed from the basins in 2004, and since then, Hanford workers have been dealing with the radioactive sludge that remains.
"Capturing the sludge from the settler tubes ... will pave the way for complete removal and supports DOE's vision of completing cleanup along the Columbia River by 2015," said Matt McCormick, manager of the Department of Energy Hanford Richland Operations Office, in a statement.
CH2M Hill Plateau Remediation Co. was able to empty the settler tubes of more than99 percent of the sludge they held, said Michael Johnson, CH2M Hill director of the sludge treatment project. It used a vacuum system combined with a high pressure spray that periodically knocked sludge loose.
Now the settler tube sludge is held in a sixth underwater container in the K West Basin. The water is needed to shield workers from radiation.
Engineers and technicians spent more than two years designing and testing tools for the retrieval. A mock-up of a settler tube at the Maintenance and Storage Facility near the Fast Flux Test Facility was used for workers to practice with long-handled tools.
For the work at the K West Basin, operators and radiological control technicians, dressed in layers of radiation-protection clothing and respiratory equipment, used 22- to 25-foot long tools to reach to the bottom of the basin to the settler tubes.
Workers took about six months to empty the 10 horizontal settler tubes, each 16 feet long.
"Retrieval of this waste allows us the opportunity to complete sampling and determine the best method for treatment and removal of the sludge," said John Lehew, CH2M Hill president.
Small portions of the settler tube sludge will be sent in lead-lined containers to Pacific Northwest National Laboratory for analysis of its chemical and physical properties.
The settler tube sludge has been troubling because so little is known about it, Johnson said. Held inside the tubes, it could not been seen or handled.
The sludge particles are very abrasive and CH2M Hill wants more information on what affect the sludge could have on pumps and components as it designs equipment to retrieve the sludge from its underwater container and pump it from the basin.
It also wants information on how quickly the sludge settles and measurements of radiation and the types of isotopes it contains.
The analysis will not only provide information to help pump the sludge out of its new container and the basin, but Lehew said it also will "provide a higher level of confidence when we treat the sludge."
CH2M Hill has been sampling the sludge vacuumed from the floors of the basins since last summer.
Sampling of the settler tube sludge should being in a few weeks and all sampling is expected to be completed this year.
* Annette Cary: 509-582-1533; email@example.com; More Hanford news at hanfordnews.com.