Mixed Waste Encapsulation in Polyester Resins. Treatment for Mixed Wastes Containing Salts. Mixed Waste Focus Area. OST Reference #1685
Throughout the Department of Energy (DOE) complex there are large inventories of homogeneous solid mixed wastes, such as treatment residues, fly ashes, and sludges that contain relatively high concentrations (greater than 15% by weight) of salts. The inherent solubility of nitrate, sulfate, and chloride salts makes traditional cement stabilization of these waste streams difficult, expensive, and challenging. Salts can effect the setting rate of cements and can react with cement hydration products to form expansive and cement damaging compounds. Many of these salt wastes are in a dry granular form and are the by-product of treating spent acidic and metal solutions used to recover and reformulate nuclear weapons materials over the past 50 years. At the Idaho National Engineering and Environmental Laboratory (INEEL) alone, there is approximately 8,000 cubic meters of nitrate salts (potassium and sodium nitrate) stored above ground with an earthen cover. Current estimates indicate that over 200 million kg of contaminated salt wastes exist at various DOE sites. Continued primary treatment of waste water coupled with the use of mixed waste incinerators may generate an additional 5 million kg of salt-containing, mixed waste residues each year. One of the obvious treatment solutions for these salt-containing wastes is to immobilize the hazardous components to meet Environmental Protection Agency/Resource Conservation and Recovery Act (EPA/RCRA) Land Disposal Restrictions (LDR), thus rendering the mixed waste to a radioactive waste only classification. One proposed solution is to use thermal treatment via vitrification to immobilize the hazardous component and thereby substantially reduce the volume, as well as provide exceptional durability. However, these melter systems involve expensive capital apparatus with complicated off-gas systems. In addition, the vitrification of high salt waste may cause foaming and usually requires extensive development to specify glass formulation recipes. As an alternative to thermal treatments, low-temperature stabilization of these materials in basic cementitious grouts has also been widely employed. However, salts interfere with the basic hydration reactions of Portland cement, leading to an inadequate set or deterioration of the waste form over time. Sufficient and compliant stabilization in cement can be achieved by lowering waste loadings, but this involves a large and costly increase in the volume of material requiring handling, transporting, and disposal.
- Research Organization:
- USDOE Office of Environmental Management (EM), Washington, DC (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- OSTI ID:
- 1248048
- Report Number(s):
- DOE/EM-0480
- Country of Publication:
- United States
- Language:
- English
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