Use of ozone for dissolving high-level plutonium dioxide in nitric acid in the presence of Am(V,VI) ions

Abstract

Plutonium dioxide recovered in the course of reprocessing of SNF from WWER reactors (so-called high-level PuO2) was subjected to dissolution in 0.6–3.0 M HNO3 in the presence of Am(III) ions under ozonation with an ozone-oxygen mixture containing 30–180 mg l−1 O3. Measurements of the rate of the PuO2 dissolution in 3 M HNO3 in the temperature interval from 30 to 80°C showed that, with an increase in the ozone concentration in the ozone-oxygen mixture from 30 to 180 mg l−1, the dissolution rate increases by a factor of 4–5. The acceleration of the PuO2 dissolution is attributed to the formation of Am(V,VI) by homogeneous oxidation of Am(III) ions with ozone dissolved in HNO3. The Am dioxocations formed act as PuO2 oxidants and are continuously regenerated by the oxidation of Am(III) with ozone. This assumption is confirmed by an additional increase in the dissolution rate, observed on introducing Am(III) into the initial electrolyte for the PuO2 dissolution.