Co-extraction of Am(VI) and the major actinides with tributyl phosphate

Sodium bismuthate was found to be an effective oxidant for Am in nitric acid solutions up to 6 M in concentration. However, in the presence of tributyl phosphate, americium was quickly reduced to the trivalent state, resulting in low distribution ratios. Pre-equilibration of the organic phase with bismuthate at the appropriate acid concentration was not effective at preventing americium reduction by tributyl phosphate. However, when a small amount of perchloric acid was added to the acidic, bismuthate-containing aqueous phase, much higher distribution ratios for americium extraction were achieved. Data comparing the extraction of americium to hexavalent uranium, neptunium and plutonium are presented. Slope analysis was used to confirm the extraction of americium in the hexavalent state. (authors)