Testing of low-temperature stabilization alternatives for salt containing mixed wastes -- Approach and results to date

Through its annual process of identifying technology deficiencies associated with waste treatment, the Department of Energy`s (DOE) Mixed Waste Focus Area (MWFA) determined that the former DOE weapons complex lacks efficient mixed waste stabilization technologies for salt containing wastes. These wastes were generated as sludge and solid effluents from various primary nuclear processes involving acids and metal finishing; and well over 10,000 cubic meters exist at 6 sites. In addition, future volumes of these problematic wastes will be produced as other mixed waste treatment methods such as incineration and melting are deployed. The current method used to stabilize salt waste for compliant disposal is grouting with Portland cement. This method is inefficient since the highly soluble and reactive chloride, nitrate, and sulfate salts interfere with the hydration and setting processes associated with grouting. The inefficiency results from having to use low waste loadings to ensure a durable and leach resistant final waste form. The following five alternatives were selected for MWFA development funding in FY97 and FY98: phosphate bonded ceramics; sol-gel process; polysiloxane; polyester resin; and enhanced concrete. Comparable evaluations were planned for the stabilization development efforts. Under these evaluations each technology stabilized the same type of salt waste surrogates. Final waste form performance data such as compressive strength, waste loading, and leachability could then be equally compared. Selected preliminary test results are provided in this paper