Actinides recovered from nitric acid

Actinide retention increases with increasing nitric acid concentration. Tetravalent actinides are more strongly retained than trivalent actinides. Chloro complexes of tetravalent and hexavalent actinides, but not trivalent actinides, are retained from hydrochloric acid solutions (see Figure 9.12). Actinides retained on TRU-Resin columns from nitric acid load solutions can be recovered, individually or in groups, using different acid solutions and/or complexants as eluents. In addition, on-column redox chemistry can be used to shift the valence state of Pu through multistep separation processes so that Pu can be isolated individually. 

Molten salt extraction residues are processed to recover plutonium by an aqueous precipitation process. The residues are dissolved in dilute HC1, the actinides are precipitated with potassium carbonate, and the precipitate redissolved in nitric acid (7M) to convert from a chloride to a nitrate system. The plutonium is then recovered from the 7M HNO3 by anion exchange and the effluent sent to waste or americium recovery. We are studying actinide (III) carbonate chemistry and looking at new... 

Reactive solvent extraction can then be used to recover the actinides from such scrub solutions, not by extracting the actinides but rather by extracting the degradation products [22] into an alcohol solvent layer. Acidihcation of carbonate scrub washes with nitric acid destroys the carbonate and forms an interfacial crud that floats to the top of the aqueous phase. This crud is similar in behavior to that formed by acidihed lignin. 

During the decontamination steps, acid streams containing small amounts of actinides and fission products are produced. These streams are evaporated to concentrate the metal ions and recycle them. Nitric acid is recovered from the condensates and recycled. Excess HNO3 may be destroyed by formaldehyde. Fission product concentrates are routed to the aqueous raffinate of the first extractor of the partitioning cycle which contains > 99% of the FP. This constitutes the high level liquid waste (HLLW, or alternatively called HAW, high active waste). All other liquid wastes can be subdivided into intermediate level waste... 

Pu, Am, Cm 5 X 10 M) in the presence of several fission product contaminants in a synthetic waste of PUREX origin. A solution of 0.5 M formic acid and 0.1 M sulfuric acid was utilized as the receiving phase (22,25). Some of the experimental parameters which characterized the process are listed in Table 3. With a series of 20 modules, 99.9 % of Am was recovered from 2 X 10" L of feed solution in 24 hours. In subsequent experiments, a second SLM containing 1 M Primene JM-T in decalin was connected in series to the first SLM to overcome the reduction in strippant effectiveness caused by nitric acid transport into the strippant (29,30), The second helper SLM extracted only nitric acid from the first stripping solution which was 1 M formic acid (plus 0.05 M hydroxylammonium formate in the case of Pu(IV) transport). The stripping solution for the second SLM was 4 M sodium hydroxide. Results of these laboratory-scale studies demonstrate that actinides can be efficiently removed from such effluents to the point that the resulting solution can be considered a non-transuranic waste (<100 nCi/g of disposed form). 

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