Richard T. Hallen

Thermochemical nitrate destruction

A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200° C. to about 600° C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

Filtration, Washing, and Caustic Leaching of Hanford Tank AZ-101 Sludge

Abstract: Approximately 4.3 kg of slurry from Hanford Tank AZ-101 were evaluated by the pretreatment processes of cross-flow filtration, washing, caustic leaching, and rinsing. The filterability was measured with a 0.1-μm sintered metal filter using a single-element, cross-flow filtration system. During testing, the permeate flux and slurry axial velocity, pressure, and temperature were monitored every 10min. The slurry temperature was maintained at 25°C ± 5°C, except during the elevated-teniperature leaching step. The test results show that cross-flow filtration provides excellent separation of solids and liquids, as evidenced by the permeate flux and the measured activity of nearly insoluble 241Am. The average permeate flux measured was higher than the Waste Treatment Plant target of 0.014 gpm/ft2, and the average decontamination factor for 241Am was 985,000 during testing.

Sizing and Desizing Polyester / Cotton Blend Yarns Using Liquid Carbon Dioxide:

We report a preliminary investigation of nonaqueous sizing and desizing where liquid carbon dioxide is the solvent. New size formulations are required for this process because traditional size materials are not directly soluble in liquid carbon dioxide. Candidate size compounds are first tested for solubility, and those found to be soluble are then applied to polyester/cotton yarns using two methods: immersing the yarn in a size-saturated carbon dioxide solution and drawing the yarn through a hot melt of the compound. The tensile strength and elastic modulus of the sized yarns are deter mined. Complete removal of the size compounds from the treated yarns by means of liquid carbon dioxide extraction is demonstrated.

Assessment of the Mechanisms for Sr-90 and Tru Removal from Complexant-Containing Tank Wastes at Hanford

Abstract: Small-scale tests (˜20mL) were conducted with samples from Hanford underground storage tanks AN-102 and AN-107 to assess the mechanisms for removing Sr-90 and transuranics (TRU) from the liquid (supernatant) portion of the waste. The Sr-90 and TRU must be removed (decontaminated), in addition to Cs-137 and the entrained solids, before the supernatant can be disposed of as low-activity waste. Experiments were conducted with various reagents and modified Sr/TRU removal process conditions to more fully understand the reaction mechanisms. The optimized treatment conditions—no added hydroxide, addition of Sr (0.02 M target concentration) followed by sodium permanganate (0.02 M target concentration) with mixing at ambient temperature—were used as a reference for comparison. The waste was initially two orders of magnitude undersaturated with Sr; the addition of nonradioactive Sr(NO3)2 saturated the supernatant, resulting in isotopic dilution and precipitation of Sr-90 as SrCO3. The reaction chemistry of Mn species relevant to the mechanism of TRU removal by permanganate treatment was evaluated, along with the importance of various mechanisms for decontamination, such as precipitation, absorption, ligand exchange, and oxidation of organic complexants. For TRU removal, permanganate addition generally gave the highest DF. The addition of Mn of lower oxidation states (II, IV, and VI) also resulted in good TRU removal, as did complexant oxidation with periodate and addition of Zr(IV) for ligand exchange. These results suggest that permanganate treatment leads to TRU removal by multiple routes.