AMEC Tests Prove Successful For Radioactive Waste Remediation
Two full-scale GeoMelt® tests by AMEC have proved promising for the future remediation of radioactive waste at the world's largest environmental cleanup project - the Hanford Site in Washington state.
AMEC's GeoMeltâ process uses electrodes to melt contaminated waste and soil at temperatures that can reach 3,600 degrees Fahrenheit (2,000 degrees Celsius). When the melt hardens, hazardous inorganic and radioactive contaminants are permanently trapped in a glassy, solid mass that is 10 times stronger than concrete.
One of AMEC's tests focused on the future underground treatment of buried vertical shafts containing nuclear waste. The other test is part of an on-going demonstration program supporting the eventual retrieval and treatment of millions of gallons of radioactive waste stored in underground tanks. The test associated with the vertical shafts was performed under a contract with the U.S. Department of Energy. The test supporting the tank waste program was performed under contract for the Department of Energy's Office of River Protection and its prime contractor at the Hanford site, CH2M-HILL Hanford Group, Inc.
"We obviously are very pleased with the results, which will allow both processes to move forward for further testing," said Don Fraser, director of worldwide GeoMelt® operations.
For the vertical shaft test, a mock-up of the more than 140 underground waste-storage shafts at Hanford was developed. The mock-up - like the actual Hanford shafts - consisted of five bottomless and topless 55-gallon drums that were welded end-to-end and buried. The mock-up was filled with simulated waste including steel, wood, concrete and soil and chemical simulants. It is anticipated that the actual Hanford shafts contain plutonium, uranium, cesium and other highly active waste, making excavation before treatment unsafe due to high dose rates and the possibility of spontaneous chemical reactions.
The vertical shaft test successfully melted the entire shaft in just seven days, resulting in a monolith that matched its predicted size.
The second test also used simulated waste and concerned the above-ground treatment of low activity radioactive tank waste in special refractory-lined containers. GeoMelt® is under consideration for the treatment of between 30 and 70 percent of Hanford's estimated 42 million gallons of low-activity tank waste.
In this test, called bulk vitrification, the container and its liner system performed to expectations and a 42-metric-ton glass monolith was produced in eight days.
The test results will allow both procedures to advance for further testing. The next test for the vertical shaft process will be on an actual shaft at either Hanford or the Los Alamos National Laboratory site in New Mexico. Further testing of the bulk vitrification process will include the treatment of up to 300,000 gallons of actual tank wastes at the Hanford site as part of a demonstration program.
AMEC's GeoMelt® process already has been used in project on three continents to successfully treat a wide range of contaminants, including polychlorinated biphenyls (PCBs), dioxins, pesticides, herbicides, mixed radioactive wastes and a variety of heavy metals. All classes of contaminants can be treated and virtually all types of debris can be accommodated, including drums, scrap metal, concrete, boulders, asphalt, wood, tires and plastic.
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