Influence of temperature on the corrosion of uranium dioxide nuclear fuel

The anodic dissolution Of UO2 has been studied at 60 degrees C and the results compared to previous observations at 22 degrees C. The rate of oxidation/dissolution was determined electrochemically at constant potentials in the range -500 mV to 500 mV (vs. SCE). The composition of the electrochemically oxidized surface was determined by X-Ray Photoelectron Spectroscopy (XPS). The onset of oxidation (UO2 -> UO2+x) occurred at approximately the same potential (400 mV) at both temperatures. However, the conversion of U-V to U-VI, and hence to soluble UO22+, was accelerated by temperature. This acceleration of dissolution caused the development of acidity at localized sites on the fuel surface at lower (less oxidizing) potentials (>= 100 mV) at 60 degrees C than at 22 degrees C (>= 3,50 mV).