Mechanism of the rapid dissolution of Pu02 under oxidizing conditions and applications

Until the recent years, plutonium dioxide was known to be among the metallic oxides the most difficult to dissolve. From thermodynamic calculations it can be predicted that PuO2 will dissolve under oxidizing conditions. This can be achieved using Ag(II) species possibly regenerated by electrochemical means. The mechanism of such a process has been elucidated using carbon paste electrochemistry and 18O labelling. These studies demonstrate that the chemical reaction limiting the overall proces is located on the surface of the solid PuO2, and that the first step consists in the oxidation of the plutonium into Pu(V) species. Applications of the dissolution process of PuO2 by electrogenerated Ag(II) were growing in the recent years in FRANCE. These applications developed often in collaboration with SGN and COGEMA, concern the treatment of: out of specifications PuO2, incineration ashes, wastes produced during MOX fuel fabrication, and during the dismantling of old nuclear facilities. A general overview of these different applications is given