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In this study, the effect of light on the kinetics and speciation of plutonium at its interaction with particles of TiO2 under different light conditions is shown for the first time. It was found that sorption was followed by reduction of the plutonium to Pu(IV). In this, the reduction reaction and sorption in conditions of the presence of light proceed significantly more rapidly due to the photocatalytic activity of titanium dioxide, providing a source of electrons for the reaction. Spectral methods (XAFS and TEM) showed that plutonium forms nanoclusters with the structure of PuO2, which decorate the surface of the solid phase. [ABSTRACT FROM AUTHOR]

Plutonium partitioning and speciation was studied under the conditions of a liquid nuclear waste repository site. The dominating effect of corrosion products (Fe and Cr) oxides on plutonium partitioning was established in batch sorption tests at 150 ℃ and by using sequential extraction. Various techniques including Mössbauer spectrometry, XRD and TEM were used to characterize Fe/Cr oxide phases that form both precipitates and surface coatings which sorb plutonium. The sorption and speciation of plutonium was modeled thermodynamically using Pourbaix diagram that takes into account both surface complexation reaction and precipitation of insoluble PuO2. [ABSTRACT FROM AUTHOR]