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Communications and External Relations
New waste management tool may increase efficiency and savings
OAK RIDGE, Tenn.,
Feb. 21, 1997
While working on some glass composition experiments at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL), researcher George Parker stumbled onto a waste treatment solution that is more efficient and less expensive.
During the experiments, Parker noticed that his stainless steel tools were disappearing in a solution he made. While the experiments were designed to find glasses that could oxidize certain metals, the rapid dissolution of corrosion-resistant stainless steel was surprising. He consulted researcher Ed Beahm, who supported Parker's claim through a series of calculations.
Parker, Beahm and Charles Forsberg soon realized that Parker's discovery of a solution that could quickly dissolve anything could be used to immobilize waste in glass form. This technology became part of the unique system called GMODS (Glass Material Oxidation and Dissolution System).
The GMODS one-step process converts a variety of waste forms, including metals, ceramics and amorphous solids, to high-quality waste glass using the dissolution glass, which Parker discovered. It also separates halogens from the wastes and oxidizes organics, converting their residue into glass. The process result is a high-quality waste product ready for storage and designed to meet Environmental Protection Agency criteria for chemically non-hazardous waste forms.
"Waste management systems can be split into two categories: those that treat well-defined wastes and produce a high-quality product and those that treat complex mixtures and produce an inferior waste form," researcher Charles Forsberg said. "What we don't have on the market is an economical way to turn complex mixtures into a high-quality waste form."
The researchers found that the dissolution glass enabled them to separate chlorides from the waste as sodium chloride (table salt) and oxidize any metal or organic compounds that may be present in one step. Conventional systems require that non-oxide materials - the majority of waste - be oxidized before they can be combined with the glass, which adds a step and increases the cost.
Glass is the preferred waste immobilization method internationally because it has a low leach rate in groundwater. The glass that is formed through GMODS will be contained in canisters and buried underground. Forsberg looks to the ocean for examples of good waste forms.
"The ocean beach could be considered a 4 billion-year-old leaching experiment to determine what are good waste forms," he said. "The good waste forms are the materials that make long-lasting beach sand. The poor materials, such as salts, are those that are dissolved in the ocean." A process that makes glass and separates salt from the waste is needed to make a good waste form.
Failure has daunted those trying to develop a high-quality waste product through systems similar to GMODS. Most systems have no way to remove those elements in the waste that make poor-quality glass.
"We were able to overcome this problem by converting the waste materials into storage materials through induction heating and chemical reaction, which occurs when the dissolution glass and waste combine," Parker said. "This process makes it possible to keep the temperature low and prevents the production of new and unwanted materials that must be converted for storage."
One U.S. patent for GMODS has been granted and one is still pending. A European patent is also pending.
Forsberg, Beahm and Parker began working on the project in 1991. Funding came from a program entitled "Use of Glass Sacrificial Oxides to Dissolve Spent Fuel." Today, researchers are seeking funding to continue the work. With the additional funding, ORNL researchers will build a pilot plant to develop GMODS for applications on an industrial scale.
ORNL, one of DOE's multiprogram research facilities, is managed by Lockheed Martin Energy Research Corp.