Counter-current extraction of uranium and lanthanides from simulated high-level waste using N,N,N′,N′-tetraoctyl diglycolamide

A mixture of N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N-dihexyl octanamide (DHOA) dissolved in NPH has been evaluated for actinide partitioning from simulated high-level waste by cold tests in mixer–settler runs. The feed solution was a synthetic purex raffinate of pressurized heavy water reactor (PHWR) origin where lanthanides were taken as stand-in for trivalent actinides. Quantitative extraction (forward and backward) of trivalent lanthanides was observed in four stages each. Elements such as Fe, Mn, Ni, Ba and Cs were practically un-extracted. However, Cr and Mo were partially co-extracted. Reusability of the organic phase in five successive cycles suggested excellent hydrolytic stability of the reagent. Though the solvent system was susceptible to radiolytic degradation, negligible effects on the extraction as well as on the stripping of lanthanides were observed with solvent irradiated to 100 KGy radiation dose.