RICHLAND — One of the most contaminated buildings at Hanford, the 209 East Critical Mass Laboratory, has been demolished.
The 8,979-square-foot building was used for more than two decades for research on plutonium and uranium solutions to identify controls for uncontrolled nuclear reactions called criticalities.
After research stopped in the central Hanford lab in 1983, most of the radioactive materials were removed and the tanks and pipelines were flushed. But work to clean out the building to prepare for demolition still took almost two years of work by CH2M Hill Plateau Remediation Co.
It is one of the most contaminated of the 118 buildings CH2M Hill has removed since its contract for central Hanford cleanup began in 2008, requiring extensive characterization of contamination and the development and testing of techniques for the building's complex contaminated structures.
Built in 1960 during the height of the Cold War, the lab was one of three buildings of its type in the nationwide DOE complex. Battelle used the lab at Hanford for experiments to test the criticality limits of radioactive solutions.
The building included an administration section and control area where experiments could be remotely monitored and controlled, plus a contaminated mixing room and a contaminated criticality assembly room.
The lab had highly radioactive tanks, including two underground storage tanks beneath 2.5 feet of concrete.
Two long, narrow tanks -- 20 feet long by 2 inches wide and 4 feet high -- that were above ground in the lab were used to control solutions to prevent criticalities, said Mike Swartz, deputy project manager.
Workers developed a "cutting shroud" to allow those tanks to be cut up and removed in pieces. The long tanks were slid into the stainless steel shroud and then 2-foot sections were cut off and bagged to protect workers. Workers first practiced with the cutting shroud in a nonradioactive environment to test the tools and get techniques down pat before the tank work was done this summer.
In addition, glove boxes contaminated with plutonium and piping insulation containing asbestos also had to be removed.
"Due to the history of the facility and the contamination of the remaining structure, additional controls were put in place to protect the environment and the workforce, such as enhanced dust suppression, continuous perimeter air sampling and fixative applications," Kurt Kehler, CHPRC vice president of decommissioning and demolition, said in a statement.
Despite the significant radioactive contamination in the laboratory, the work was done with no spread of contamination outside control zones, Swartz said. Some of the waste removed from the lab had plutonium contamination at high enough levels to require it to be packaged for shipment to the Waste Islolation Pilot Plant, a national repository in New Mexico.
The robust construction of the building added to the time needed to demolish the building with heavy equipment. The criticality assembly room had 5-foot-thick walls and a 3-foot thick vault door made of steel and reinforced concrete also had to be removed.
The building debris was taken to the Environmental Restoration Disposal Facility in central Hanford.
Crews also have faced bad weather with cold days of heavy fog and frost this winter.
"The Department of Energy's goal is to remove any buildings that are no longer of service on the site," Al Farabee, DOE project director, said in a statement.
Tearing down the lab is part of DOE's strategy to reduce long-term surveillance and maintenance costs and shrink the contaminated footprint of Hanford to 75 square miles or less by 2015.
Hanford was used during World War II and the Cold War to produce plutonium for the nation's nuclear weapons program.