In January, Rust Federal Services of Anderson, South Carolina signed a Cooperative Research and Development Agreement with Westinghouse Savannah River Company, the U.S. Department of Energy's managing and operating contractor at its Savannah River site near Aiken, South Carolina. The cooperative agreement is sponsored by DOE's Office of Technology Development for developing and demonstrating pilot-scale vitrification processes to be used on actual Department of Energy low-level mixed waste.
Work under the CRADA will bridge crucible-scale "proof-of-priniciple" demonstrations to the eventual field tests of a transportable vitrification unit. Successful crucible-scale tests took place at DOE's Oak Ridge site with one of its mixed hazardous waste streams. The CRADA will provide the next step in the process by supporting pilot-scale demonstrations at Rust's Clemson Technical Center in Anderson, South Carolina. The demonstration will lead to a field-scale test of a transportable vitrification unit for stabilizing mixed waste at Oak Ridge.
Vitrification, a process whereby mixed waste is transformed into safe, disposal glass, is a promising alternative to incineration or cementation. A low-level mixture of hazardous and radioactive waste is placed in a melter and heated with electrodes to a molten state. As it cools, the waste solidifies into a stable, leach-resistant glass. Economic and environmental benefits deriving from vitrification are waste volume reduction and final waste-form stability. The smaller volume reduces disposal costs. The long-term durability and leach resistance of the waste glass could lead to it being delisted, or removed, from the Environmental Protection Agency's list of hazardous wastes. Delisting would save costs for barriers to contain the glass and for monitoring the stored waste.
For this CRADA, a vitrification process known as Reactive Additive Stabilization Process will be demonstrated using an EnVitCo pilot-scale melter to produce 12 pounds of glass product per hour. RASP promotes enhanced solubility of hazardous and heavy metals in the materials vitrified. Vitrification using RASP has been shown to extend the glass forming region in a soda-lime-silica glass forming system and to minimize melter refractory corrosion.
The pilot-scale demonstrations are planned for October at Rust's Clemson Technical Center using an EnVitCo melter supplied by Westinghouse and low-level mixed waste from DOE's Oak Ridge site. A continuous run of a particular waste stream is expected to last from four to eight days. Along with feed preparation, decontamination of the melter after the run, and report writing; a single demonstration could last up to two months. The two-year CRADA will include several runs using various waste streams. Rust will be responsible for instrumentation and engineering control, waste pretreatment, and materials handling. Westinghouse personnel will contribute glass formulation, process modeling, melter operations expertise, and off-gas treatment.
