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22 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Results of The Solvent Hold Tank Disposal Sample

Multiple samples from the Solvent Hold Tank (SHT) at the Modular Caustic-Side Solvent Extraction Unit (MCU) were delivered to SRNL and composited for comprehensive analysis in support of a disposal pathway for this organic liquid. A suite of radiochemical and nonradiochemical analyses show that the solvent composition is as expected with respect to the solvent components. The radiochemical analyses confirm the assumption that very few radioactive species are associated with the solvent (other than cesium) and those that have measurable values are typically a few tens of pCi/mL in activity concentration. The solvent has a total activity of ≤1.99E- 08 Ci/g, or ≤6.27E-05 Ci/gal. The cesium in the solvent has an activity of ≤1.76E-08 Ci/g, or ≤5.55E-05 Ci/gal. For the non-radiochemical analyses, the results are as anticipated. The solvent shows no or minimal propensity to take up Resource Conservation Recovery Act (RCRA) metals, except for mercury, likely due to uptake of methyl-mercury compounds known to be in the feed stream.

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DOE OSTI2021

Density of Next-Generation Caustic-Side Solvent Extraction Solvent

This report recommends the appropriate modifier concentration to employ in the Next Generation Solvent (NGS) to be used in the Salt Waste Processing Facility (SWPF) at the Savannah River Site for removal of cesium from legacy tank waste. The Next Generation Caustic-Side Solvent Extraction (NG-CSSX) process employing the NGS is a marked improvement over the original Caustic-Side Solvent Extraction (CSSX) process, as it provides more effective removal of cesium from highly alkaline radioactive wastes and concentrates this removed cesium into an aqueous solution that is easy to vitrify for final disposal. Considerable effort has been devoted to optimizing the chemistry and process conditions of both systems, and their effectiveness has been demonstrated at the pilot scale at the Modular CSSX Unit (MCU). Due to the success of the demonstration and pilot-scale tests, the Salt Waste Processing Facility (SWPF) has been built to process larger volumes of waste with the CSSX process. To accelerate the waste-processing rate of the SWPF beyond its design throughput, plans call for the replacement of the CSSX process by the NG-CSSX process. To implement the NG-CSSX process in equipment optimized for CSSX, adjusting the density of the NGS to match the CSSX solvent density of 0.851 ± 0.0008 g/mL is considered advisable to obtain comparable hydraulic performance. Toward this objective, the density of the NGS has been measured at different temperatures and modifier concentrations to determine that a concentration of 0.650 M Cs-7SB modifier provides the best match for the desired density.

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DOE OSTI2022

Physical Properties of the Salt Waste Processing Next Generation Solvent Formulation

In 2020, a review team examined the risks associated with the implementation of a new solvent formulation, similar to what was used in Modular Caustic-Side Solvent Extraction Unit (MCU). The team identified a number of risks associated with the change and pathways to mitigate some of the risks. SRNL has been tasked with examination and testing of a Salt Waste Processing Facility (SWPF) formulation for a Next Generation Solvent (NGS) intended for use at that facility. This formulation is known as the “$NGS\tiny{OPTIMUM}$”. This formulation consists of: 50 mM MAXCalix; 3 mM TiDG•HCl; 0.65 M Modifier; Remainder Isopar-L™. SRNL examined several physical aspects of this solvent in order to confirm its suitability for use at SWPF, such as viscosity, dispersion, surface tension, and third phase formation. Results indicate no unusual properties of this solvent when compared to the current “BOBCalix” solvent in use at SWPF.

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DOE OSTI2022

Results of the Analyses of the SRNL Solvent Components

At the request of the Savannah River Mission Completion (SRMC), personnel at Savannah River Site (SRS) performed analyses on the remaining solvent components that are being stored at the Savannah River National Laboratory (SRNL). This was done to determine if the remaining stock of materials were still suitable for use for the Salt Waste processing Facility (SWPF). Two drums of Modifier, two drums BOBCalix, four drums of MAXCalix, and four jars of TiDG*HCl were analyzed. All were found to be of acceptable purity for use.

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