Conversion of Idaho National Engineering and Environmental Laboratory radioactive sodium-bearing waste into a single solid waste form by evaporation was demonstrated in both flask-scale and pilot-scale agitated thin film evaporator tests. A sodium-bearing waste simulant was adjusted to represent an evaporator feed in which the acid from the distillate is concentrated, neutralized, and recycled back through the evaporator. The advantage to this flowsheet is that a single remote-handled transuranic waste form is produced in the evaporator bottoms without the generation of any low-level mixed secondary waste. However, use of a recycle flowsheet in sodium-bearing waste evaporation results in a 50% increase in remote-handled transuranic volume in comparison to a non-recycle flowsheet. iv SUMMARYConversion of surrogate Idaho National Engineering and Environmental Laboratory (INEEL) sodium-bearing waste (SBW) into a single solid waste form by evaporation was demonstrated in flask-scale and pilot-scale agitated thin film evaporator (ATFE) tests. The advantage to this flowsheet is that a single remote-handled transuranic (RH-TRU) waste form is produced without the generation of a secondary waste stream from the condensation of evaporator overheads (i.e., distillate).Producing a single waste form in this manner requires that acid in the evaporator overheads be concentrated, neutralized, and recycled. This report presents results from the flask-scale and pilot-scale ATFE tests that were run to evaluate an "SBW with overhead recycle evaporation flowsheet." Three different surrogate waste feeds were tested at the flask-scale including simulated waste feed compositions that would result from neutralizing the overheads with sodium, aluminum, or magnesium and blending this recycle stream with simulated SBW. The flask-scale tests were completed to identify appropriate mass reduction ratios for each of the three recycle flowsheets. Solid evaporator bottoms product characteristics, such as pourability, solidification capability, and product toughness (e.g. hardness, non-friable/monolithic), were evaluated for acceptability. This included an evaluation of the effects of overhead recycle on bottoms product characteristics. The SBW with aluminum and magnesium recycle flowsheets yielded bottom waste form products with acceptable characteristics. However, the SBW with sodium recycle flowsheet feed formed crystals in the evaporation flask and had to be concentrated more than the others to produce a solid bottoms waste form upon cooling. Based on the results of the flask-scale tests, only the aluminum and magnesium recycle feeds were tested in the pilot-scale ATFE.ATFE pilot-scale tests yielded bottoms product with desirable characteristics for both of the simulated waste feeds tested. However, neutralizing with magnesium oxide would be the preferred choice for producing a single waste form with overhead recycle. The original concept of direct evaporation was based on the ability of aluminum nitrate to chemically bond with nine m...

The Idaho Nuclear Technology and Engineering Center (INTEC) is considering vitrification to process liquid sodium-bearing waste. Preliminary studies were completed to evaluate the potential secondary wastes from the melter off-gas clean up systems. Projected secondary wastes comprise acidic and caustic scrubber solutions, HEPA filters, activated carbon, and ion exchange media. Possible treatment methods, waste forms, and disposal sites are evaluated from radiological and mercury contamination estimates.iv v SUMMARYThe High-Level Waste Program is considering vitrification of the liquid sodium-bearing waste stored at the Idaho Nuclear Technology and Engineering Center which is part of the Idaho National Engineering and Environmental Laboratory. Several secondary wastes are anticipated from the melter off-gas clean up system, such as acidic and caustic scrubber solutions, HEPA filters, activated carbon, and ion exchange media. These wastes are expected to be designated as mixed low-level wastes. Initial scoping studies were completed to evaluate possible disposal paths for these wastes. The radiological and land disposal regulations as well as the individual site waste acceptance criteria were considered to anticipate treatment methods, waste forms, and disposal sites for each waste stream.

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This research and engineering assessment examined a microbial phosphate solubilization process as a method of recovering phosphate from phosphorus containing ore compared to the existing wet acid and electric arc methods. This activity was initiated in 1987 as an element of the Office of Conservation and Renewable Energy's Energy Conservation and Utilization Technology Program and has been supported by the public sector for its duration. A total of 860 microbial isolates, collected from a range of natural environments were tested for their ability to solubilize phosphate from rock phosphate. Based on this screening of microorganisms, a bacterium (Pseudomonas cepacia) was selected for extensive characterization and evaluation of the mechanism of phosphate solubilization and of process engineering parameters necessary to recover phosphate from rock phosphate. These studies found that concentration of hydrogen ion and production of organic acids arising from oxidation of the carbon source facilitated microbial solubilization of both pure chemical insoluble phosphate compounds and phosphate rock. Genetic studies found that phosphate solubilization was linked to an enzyme system (glucose dehydrogenase). Process-related studies found that a critical solids .density of 1% by weight (ore to liquid) was necessary" for optimal solubilization. An engineering analysis evaluated the cost and energy requirements for a 2 million ton per year sized plant, whose size was selected to be comparable to existing wet acid plants. The water handling and holding requirements made the conceptual bioprocess plant uneconomical. An optimized process was postulated based on increasing soluble phosphate concentration from 200 mg/L to 20,000 mg/L. The optimized process was shown to be feasible and comparable in energy consumption to that of the wet acid process, lt was considerably less energy intensive when compared to the oxidation method. Based on the findings of this study, a research plan was developed for future phosphate solubilization research.