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 ta sk. Until the 1980s few dissolution processes existed except those bas ed on the use of highly corrosive solutions consisting of nitric and h ydrofluoric acids at boiling temperature. Thermodynamics calculations suggest that PuO2 dissolution can be achieved under strong oxidizing o r reducing conditions, however. Basic results dealing with the reducti ve 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 var ious physicochemical conditions. The electron transfer mechanism was i nvestigated by applying O-18-labelling techniques, which provided stri king evidence of the pure heterogeneous nature of the electron transfe r reaction.