Electrochemical study of the influence of pH and carbonate species concentration on the dissolution of depleted UO₂

In Belgium, the current reference concept for the final disposal of spent nuclear fuel is the so-called supercontainer design, in which spent nuclear fuel is placed in a watertight carbon steel container which will be surrounded by a concrete buffer. In this context, this work compares the electrochemical analysis of depleted UO₂ in alkaline and anaerobic conditions with and without carbonate species. In presence of carbonates, the open circuit potential is lower and can reach a potential where the oxidative dissolution is no more present. At pH 9.5 without carbonate species, 1/R_p is the lowest, while it increases with the increase of the carbonate concentration. However, whatever the system studied the uranium concentration in solution remains below the solubility level of U^IV. Finally, cyclic voltammetry shows a similar behaviour for all test conditions. Graphical abstract: (Figure presented.)