Use of a mixture of trpo and tbp for the partitioning of actinides from high-level waste solutions of purex origin and its comparison with cmpo and other phosphorus-based extractants

摘要

The partitioning of long-lived alpha-emitting actinides, present in high-Ievel radioactive waste (HLW) solutions from PUREX reprocessing of spent nuclear fuels, has been carried out us- ing a commercially available, reasonably inexpensive, trialkylphos- phine oxide (TRPO), Cyanex-923 alone or its mixture with tri-n- butylphosphate (TBP) in dodecane. The studies have been carried out from nitric acid as well as from three types of synthetic HLW solutions. With 30% TRPO alone, third-phase formation was ob- served when HLW in 3.0 M HNO_3 was taken as such. With the mix- ture ofTRPO and TBP, it has been shown that the HLW need not be diluted 10 times, but only the acidity has to be reduced from approx 3 to approx 1 M (without substantial dilution) to achieve an efficient separa- tion of the minor actinides. The results thus obtained using TRPO has been compared with those already reported while using dihexyl- N ,N -diethylcarbamoylmethyl phosphonate, diisodecyl phosphoric acid, and octyl(phenyl)N ,N -diisobutylcarbamoylmethylphosphine oxide (CMPO). The mixture of 0.2 M CMPO and 1.2 M TBP in dodecane (TRUEX solvent) seems to be a superior extractant for the partitioning of minor actinides from HLW solutions.