Alternatives for High-Level Waste Salt Processing at the Savannah River Site (2000) / Chapter Skim
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Crystalline Silicotitanate Ion Exchange
Crystalline Silicotitanate Ion Exchange
Pages 55-64
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From page 55... ...
The efution sequence allows the ion exchange material to be reused in multiple cycles. Although the underlying technology is well established, ion exchange for cesium removal from high-level waste at the Savannah River Site (SRS)
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From page 56... ...
A large distribution coefficient indicates high Cs selectivity. SOURCE: Anthony et al.
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From page 57... ...
would then be added to the waste to sorb strontium, plutonium, and other actinides, and the resulting slurry would be filtered to remove insoluble MST and entrained sludge from the prior step. The insoluble solids would then be washed and transferred to Defense Waste Processing Facility (DWPF)
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From page 58... ...
CST (cesium removal) | sludge | strontium- and actinide-loaded MST cesium-loaded CST · strontium · cesium O actinides DWPF Glass - ~ | Saltstone | FIGURE 5.3 Schematic flow sheet for radionuclide removal from high-level tank waste at Savannah River using CST ion exchange.
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From page 59... ...
A fourth, proprietary dopant component (Savannah River Site, 1999) is used in the commercially available material, and a five-component system is produced by cesium exchange.
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From page 60... ...
These include the interface with MST processing for strontium and actinide removal, effect of variation in waste-feed composition, column design parameters, influence of glass formulation with higher titanium loadings on waste form performance, stability of the loaded material as a function of temperature, reproducibility of the manufactured CST, and reaction of CST in alkaline solution to form new solid phases. The committee's interim report highlighted the last two concerns, specifically noting that they would need to be resolved before the CST process could be deployed.
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From page 61... ...
The Savannah River Technology Center (SRTC) also plans to "perform an evaluation of various tank wastes during the next several years," the purpose of which is to "catalogue the cesium removal efficiencies of the currently marketed CST versus the chemical compositions of F- and H-area wastes" (Savannah River Site, ~ 999~.
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From page 62... ...
SRS plans to conduct additional tests to examine cesium removal performance in the presence of gas generation, but the specific tests to be conducted have not yet been decided. Possible tests include use of hydrogen peroxide for a non-radioactive test and the use of ORNE's High Flux Isotope Reactor for a radiation exposure test, although the applicability of such reactor-based tests has not been established.
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From page 63... ...
These difficulties could readily account for the loss of capacity. It also appears that the proprietary binder has not yet been adequately evaluated for its solubility at the high pH found in SRS wastes; the reaction of commercial CST in alkaline solution to form new solid phases may be responsible for observed decreases in column performance.
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From page 64... ...
2) The column design for the CST process was based on typical parameters such as throughput and decontamination factors, but do not appear to be optimized for thermal loadings and expected radiation fields.
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