Home / Store / Journals / Electronic Articles / Nuclear Technology / Volume 43 / Number 2 / Pages 136-145
James D. Navratil, Gary H. Thompson
Nuclear Technology / Volume 43 / Number 2 / Pages 136-145
Format:electronic copy (download)
The U.S. Department of Energy awarded Oak Ridge National Laboratory a program to develop a cost-risk-benefit analysis of partitioning long-lived nuclides from waste and transmuting them to shorter lived or stable nuclides. Two subtasks of this program were investigated at Rocky Flats. In the first subtask, methods for solubilizing actinides in incinerator ash were tested. Two methods appear to be preferable: reaction with ceric ion in nitric acid or carbonate-nitrate fusion. The cericnitric acid system solubilizes 95% of the actinides in ash; this can be increased by 2 to 4% by pretreating ash with sodium hydroxide to solubilize silica. The carbonate-nitrate fusion method solubilizes ≥98% of the actinides, but requires sodium hydroxide pretreatment. Two additional disadvantages are that it is a high-temperature process, and that it generates a lot of salt waste. The second subtask comprises removing actinides from salt wastes likely to be produced during reactor fuel fabrication and reprocessing. A preliminary feasibility study of solvent extraction methods has been completed. The use of a two-step solvent extraction system—tributyl phosphate (TBP) followed by extraction with a bidentate organophosphorous extractant (DHDECMP)—appears to be the most efficient for removing actinides from salt waste. The TBP step would remove most of the plutonium and >99.99% of the uranium. The second step using DHDECMP would remove >99.91% of the americium and the remaining plutonium (>99.98%) and other actinides from the acidified salt waste.
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