BASIC STUDIES ON THE KINETICS AND MECHANISM OF THE RAPID DISSOLUTION REACTION OF PLUTONIUM DIOXIDE UNDER REDUCING CONDITIONS IN ACIDIC MEDIA

Dissolution of PuO2 in aqueous solutions is a notoriously difficult task. Until the 1980s few dissolution processes existed except those based on the use of highly corrosive solutions consisting of nitric and hydrofluoric acids at boiling temperature. Thermodynamics calculations suggest that PuO2 dissolution can be achieved under strong oxidizing or reducing conditions, however. Basic results dealing with the reductive dissolution reaction of PuO2 with Cr-II in sulphuric acid media are presented herein. Simple heterogeneous kinetics modelling is proposed and satisfactorily accounts for the reaction rates observed under various physicochemical conditions. The electron transfer mechanism was investigated by applying O-18-labelling techniques, which provided striking evidence of the pure heterogeneous nature of the electron transfer reaction.