Uranium recovery from simulated molybdenum-99 production residue using non-dispersive membrane based solvent extraction

Abstract

Commercial alkaline dissolution molybdenum-99 (99Mo) producers are currently not recovering enriched uranium (U) from 99Mo production waste which has a unique actinide and fission product composition. During the development of a process to recover U from 99Mo production residue, the suitability of non-dispersive membrane based solvent extraction (MBSX) for this process was investigated. The residue was dissolved in nitric acid (HNO3) and extracted using tributyl phosphate (TBP). Acetohydroxamic acid (AHA) was added to the feed to prevent co-extraction of plutonium (Pu). Complete U extraction with MBSX was achieved at low U(VI) concentrations in the feed while more than one MBSX contacting step was required for high U(VI) concentrations. Ammonium carbonate ((NH4)2CO3) was investigated as an alternative stripping solution to traditionally used dilute HNO3. Almost complete U(VI) stripping (99%) from 7500mgL−1U(VI) in the organic phase was obtained in a single contacting step with 0.5M (NH4)2CO3. Practically none of the characteristic fission products present in the 99Mo production residue were extracted with AHA and also neither influencing U(VI) nor fission product extraction. The study has shown that MBSX was suitable for selective extraction (with AHA added) and stripping (0.5M (NH4)2CO3) of U(VI) from a simulated 99Mo production residue.