Glass Waste Forms for Oak Ridge Tank Wastes: Fiscal Year 1997 Report for Task Plan SR-16WT-31, Task A

Abstract

Through the Tanks Focus Area, the Office of Science and Technology has funded the Savannah River Technology Center (SRTC) and the Oak Ridge National Laboratory (ORNL) to develop formulations which can incorporate sludges from Oak Ridge (OR) Tank Farms into an immobilized waste form. SRTC has been developing a glass waste form, while ORNL has been developing a grout waste form for the tank farms sludges. The four tank farms included in this task are: Melton Valley Storage Tanks (MVST), Bethel Valley Evaporator Service Tanks (BVEST), Gunite and Associated Tanks (GAAT)and Old Hydrofracture Tanks (OHF). The first element of the SRTC task for FY97 was to develop a glass formulation to immobilize a blended sludge from the MVST and the BVEST. ORNL had previously developed a soda-lime-silicate (SLS) glass for the MVST sludge. SRTC has reproduced this work and expanded on it for the blended MVST/BVEST sludge. SRTC also performed a durability test on the resultant glasses. The normalized sodium and silicon leachate concentrations for the soda lime silica glasses readily met the Environmental Assessment glass (a borosilicate glass) benchmark limits for these two elements. Additional efforts at the SRTC included the verification of the glass formulation prior to the ORNL radioactive demonstration and technical consultations during the radioactive demonstration. However, the major emphasis for SRTC in FY97 was on the second element of this task, the overall blended average of the tank farms. The second element focused on developing a glass formulation which would immobilize a sludge with a composition obtained from averaging the contents of all four tank farms (composite composition). Although blending the contents of all four tank farms is not feasible, this average composition provides a basis from which to develop a glass formulation. Once a frit formulation was developed which produced a durable glass waste form at relatively high waste loadings, then a statistically designed approach was implemented to determine the size of the sludge compositional window which could be adequately immobilized by the frit formulation. This report summarizes the SRTC results of Task A of Task Plan SR-16WT-31 for FY97.