The dissolution of uranium oxides: Thermodynamic and kinetic investigations

• This work investigates the dissolution of various uranium oxides in nitric acid medium;
• The most predominant occurring reaction was determined on the basis of the thermodynamic and kinetic study;
• Six uranium oxides were dissolved and studied;
• The Gibbs free energies of all the reactions ΔrG°(T) were analyzed by the Ulich model;
• Three reaction order rate models were applied on the predominant reaction reported above.

This work investigates the dissolution of various uranium oxides in nitric acid medium and the most predominant occurring reaction was determined on the basis of the thermodynamic and kinetic studies. Six uranium oxides were dissolved and studied. The Gibbs free energies of all the reactions ΔrG°(T) were analyzed by Ulich model (Ulich, 1930) and the predominant dissolution reaction was found to be:3U3O8(s) + 20HNO3(aq) → 9 UO2 (NO3)2(aq) + 2NO(g) + 10H2OThree reaction order rate models namely the first, the second and the third order were applied on the predominant reaction reported above. According to the kinetics results, our reaction best fits the second order equation rate.

Variation of the free energies of dissolution of uranium oxides.Figure optionsDownload as PowerPoint slide