Determining the Release of Radionuclides from Tank 18F Waste Residual Solids [electronic resource] : FY2016 Report
- Washington, D.C. : United States. Department of Energy. Office of Environmental Restoration and Waste Management, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Physical Description:
- 57 pages : digital, PDF file
- Additional Creators:
- Savannah River National Laboratory (U.S.)
United States. Department of Energy. Office of Environmental Restoration and Waste Management
United States. Department of Energy. Office of Scientific and Technical Information
- Pore water leaching studies were conducted on actual Savannah River Site (SRS) Tank 18F residual waste solids to support Liquid Waste tank closure efforts. A test methodology was developed during previous simulant testing to produce slurries of tank residual solids and grout-representative solids in grout pore water solutions (based on SRS groundwater compositions) with pH and E<sub>h</sub> values expected during the aging of the closed waste tank. The target conditions are provided below where the initial pore water has a reducing potential and a relatively high pH (Reducing Region II). The pore water is expected to become increasingly oxidizing with time (Oxidizing Region II) and during the latter stages of aging (Oxidizing Region III) the pH is expected to decrease. For the reducing case, tests were conducted with both unwashed and washed Tank 18F residual solids. For the oxidizing cases (Oxidizing Regions II and III), all samples were washed with simulated grout pore water solutions prior to testing, since it is expected that these conditions will occur after considerable pore water solution has passed through the system. For the reducing case, separate tests were conducted with representative ground grout solids and with calcium carbonate reagent, which is the grout phase believed to be controlling the pH. Ferrous sulfide (FeS) solids were also added to the reducing samples to lower the slurry E<sub>h</sub> value. Calcium carbonate solids were used as the grout-representative solid phase for each of the oxidizing cases. Air purge-gas with and without CO<sub>2</sub> removed was transferred through the oxidizing test samples and nitrogen purge-gas was transferred through the reducing test samples during leach testing. The target pH values were achieved to within 0.5 pH units for all samples. Leaching studies were conducted over an E<sub>h</sub> range of approximately 0.7 V. However, the highest and lowest E<sub>h</sub> values achieved of ~+0.5 V and ~-0.2 V were significantly less positive and less negative, respectively, than the target values. Achievement of more positive and more negative E<sub>h</sub> values is believed to require the addition of non-representative oxidants and reductants, respectively.
- Published through SciTech Connect.
William D. King; David T. Hobbs.
- Funding Information:
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