Two basic features of actinide solution chemistry create essential and unavoidable complications in the discussion of the chemistry of these ele­ments in the nuclear fuel cycle.

First, all are radioactive, though the specific activities vary over a wide range. The important consequence of this reality is that the chemistry of these species in both aqueous and organic solutions is significantly impacted by the effects of ionizing radiation on the surroundings. In aqueous media, this implies that an overriding consideration will be the effect of hydrogen peroxide (H2O2) on the chemistry of these systems. Both oxidizing and reducing radicals are created during the radiolysis of water, hence the redox state of the light actinides is not always reliably predicted by thermody­namic factors alone. In the environment, radiolysis is a very localized phe­nomenon, of comparatively low importance in actinide solution chemistry, but it cannot be neglected entirely. Regarding used fuel processing, radioly­sis is severe with many contributing isotopes. This feature represents a dynamic contribution that, in the end, substantially impacts the accuracy of any predictions based on thermodynamic parameters.

The second complication regards the important need to separate trivalent actinides from fission product lanthanides. The actinides interact more strongly with ligand donor atoms “softer” than oxygen due to a slight enhancement in the covalency of the bonding of the actinides. This feature is exploited in every successful aqueous scheme for the separation of Am3+ and Cm3+ from lanthanides. This observation was first made by Diamond et al. in chloride-based cation exchange separations of the groups. [8]