Thermodynamic geochemical models have beenapplied to assess the relative effectiveness of a variety ofreagents added to aqueous waste streams for the removal ofradioactive elements. Two aqueous waste streams wereexamined: effluent derived from the processing of uranium oreand irradiated uranium fuel rods. Simulations of the treatmenttrain were performed to estimate the mass of reagents neededper kilogram of solution, identify pH regions corresponding tosolubility minimums, and predict the identity and quantity ofprecipitated solids. Results generated by the simulations includefigures that chart the chemical evolution of the waste stream asreagents are added and summary tables that list mass balancesfor all reagents and radioactive elements of concern. Modelresults were used to set initial reagent levels for the treatmenttrains, minimizing the number of bench-scale tests required tobring the treatment train up to full-scale operation. Additionally,presentation of modeling results at public meetings helps toestablish good faith between the federal government, industry,concerned citizens, and media groups.
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