The Department of Energy is preparing to remove radioactive sludge from Hanford's K West Basin for the first time, moving a comparatively small amount of specialized, highly radioactive material out of the area near the Columbia River.
It's the latest chapter in the ongoing saga of the difficult cleanup of the radioactive sludge that accumulated in the cooling basins of the K East and K West reactors as irradiated fuel was stored there for decades.
The fuel corroded after it was stranded in the pools after fuel processing at Hanford to remove plutonium for defense use was halted in the 1980s. It combined with dirt and bits of concrete from the pools to form a highly radioactive sludge.
The last of the 2,300 tons of fuel was removed from the basins in 2004. Since then workers have been dealing with the radioactive sludge that remains, getting it vacuumed up and consolidated in underwater containers in the sturdier K West Basin in early 2008.
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Now DOE and contractor CH2M Hill Plateau Remediation Co. plan to start in May or June moving the first batch of sludge, a small amount called the knockout pot sludge, out of the basin.
"It's a good step in the right direction," said Rod Lobos, engineer for the Environmental Protection Agency, the regulator on the project.
But the real proof of the project's success will be when the knockout pot material is out of the basin and the rest of the sludge, too, he said.
"In the scheme of sludge, this is the first step," he said.
The goal is to get sludge out of the K West Basin so the basin can be removed and the K West Reactor put in storage. It's near the Columbia River and DOE's goal is to have most environmental cleanup along the Columbia River completed by 2015. It faces a legally binding deadline to have the K West Basin removed by fall 2019.
Engineered underwater containers in the K West Basin hold about 37 cubic yards of sludge. The knockout pots have held less than half a cubic yard of sludge. They filtered out the heaviest particles removed when fuel left in the basin was washed underwater before the fuel was removed for dry storage.
To prepare to remove the knockout pot material, that sludge has been processed twice, washing and straining it to remove smaller particles and sending it through a system of cups to allow the heavier items to drop out.
"The goal was to separate the uranium and nonuranium materials from each other," said Tom Teynor, DOE project director.
The knockout pot sludge includes uranium metal fragments and uranium oxides plus lighter aluminum wires and gasket material from the fuel canisters. Plutonium, cesium and strontium also are present in much smaller quantities.
The processing separated out about 14 gallons of dense material with irradiated uranium that can be processed much as the nuclear fuel in the K Basins was. It weighs about 1,400 pounds. The material is highly radioactive, with contact radiation levels on the storage canisters ranging from 220 to 520 rad per hour.
The material will go through a final size separation and density verification and then will be packed into as many as six multi-canister overpacks before it is removed from the basin. Removal is to be completed by September.
It will be dried at Hanford's Cold Vacuuming Drying Facility and then moved for temporary storage to Hanford's Canister Storage Building, where irradiated fuel from the K Basins is being stored.
The waste eventually is expected to be sent to a national repository for spent nuclear fuel, such as the repository that was being developed at Yucca Mountain, Nev.
The water in the basin shields workers from radiation and workers must stand on grating above the basin and use long-handled tools to work with the sludge inthe 21-foot deep basin.
Workers have been training at a mockup of the K Basin in the 28,000-square-foot Maintenance and Storage Facility, which once was planned to support the Fast Flux Test Facility. They have helped develop the tools and procedures that will be used to remove the dense knockout pot sludge, Teynor said.
Work to prepare to remove the bulk of the K Basin sludge is ongoing. DOE's report on how to treat the rest of the sludge is due to EPA at the end of the month, Lobos said. Most of the sludge will be treated for shipment to the Waste Isolation Pilot Plant in New Mexico, the nation's repository for transuranic waste, such as plutonium.
-- Annette Cary: 582-1533; firstname.lastname@example.org