Hanford workers have finished clearing the deck of U Plant's canyon, preparing it to be the first of Hanford's huge processing canyons to be demolished.
The deck above the canyon was littered with 120 pieces of large equipment, including compressors and pumps, contaminated with radioactive material. Those and many smaller items, such as pieces of piping, have been lowered and fitted like puzzle pieces into the 40 former processing cells below the deck.
"U Canyon will be a model for the demolition of other canyons on the Hanford Site," said Al Farabee, Department of Energy project director, in a statement.
U Plant was one of five processing plants at the Hanford nuclear reservation built to chemically separate plutonium from fuel rods irradiated in Hanford reactors for the nation's nuclear weapons program. Never needed to process plutonium, it was used to recover uranium from waste material.
The uranium processing was done in the 810-foot-long canyon, which has high ceilings and a narrow interior that is longer than the Space Needle is tall.
CH2M Hill Plateau Remediation Co. next will fill the cells in the canyon's lower level with grout. About 20,000 cubic yards of it will be needed to fill the cells and their supporting galleries, rooms, tunnels and piping. The processing cells extend about 30 feet below the deck.
A subcontract for that work is close to being awarded and it should start in October.
That will prepare the upper section of the canyon to be demolished. An earthen cap then will be built over what remains of the canyon to prevent water from infiltrating.
CH2M Hill is preparing the canyon for demolition using $35 million in federal economic recovery funds, plus $17 million from Hanford's annual budget. Demolition could begin in 2012. DOE approved the demolition plan in 2005 but did not have money to proceed until Hanford received $1.96 billion in federal economic stimulus money.
"One of the challenges crews faced to complete this major step included using the same crane that was used back in the '50s to lift the cover blocks and place excess equipment and materials into the concrete cells beneath the canyon deck," Kurt Kehler, CH2M Hill decommissioning and demolition vice president, explained in a statement.
Getting the crane operating again and certified saved money and speeded up work, he said.
U Plant was built during World War II, but T Plant and B Plant were able to keep up with processing irradiated fuel without bringing U Plant online. It initially was used to train operators for the other two plants. In 1952, it was converted to recover uranium from waste generated by other plants and was operated for five years.
From 1957-64, it was used to decontaminate, store and maintain equipment from other processing sites. Other than some minor decontamination work, it virtually has been deserted since then until work to prepare it for demolition began. U Plant was picked as the first canyon to demolish because it never was used to process fuel to extract plutonium and is believed to be the least contaminated.