Michael E. Broczkowski

Corrosion of Nuclear Fuel Inside a Failed Copper Nuclear Waste Container

Canadas Nuclear Waste Management Organization has recommended to the Canadian federal government an adaptive phased management approach to the long-term management of used nuclear fuel. This approach includes isolation in a deep geologic repository. In such a repository, the fuel would be sealed inside a carbon steel-lined copper container. To assist the development of performance assessment models studies of fuel behaviour inside a failed waste container are underway. Using an iterative modeling and experimental approach, the important features and processes that determine fuel behaviour have been identified and studied. These features and processes are discussed and the results of studies to elucidate specific mechanisms and determine important parameter values summarized. (authors)

Influence of Noble Metal Particles on Redox Reactions on Uranium Dioxide Surfaces

The influence of rare-earth doping and noble metal inclusions (ε-particles) on H2O2 and O2 reduction and H2 oxidation on UO2 surfaces has been studied electrochemically. These reactions are important in determining the corrosion behaviour of nuclear fuel inside failed waste containers under permanent waste disposal conditions. Experiments were conducted on SIMFUEL electrodes doped with various amounts of non-radioactive elements in proportions appropriate to simulate the chemical effects of in-reactor irradiation. The results show that ε-particles catalyze all of these reactions. These results indicate that ε-particles can act as catalytic anodes and cathodes depending on the redox conditions prevailing within a failed container.

Influence of Temperature on the Corrosion of Uranium Dioxide Nuclear Fuel

The anodic dissolution of UO{sub 2} has been studied at 60 deg. C and the results compared to previous observations at 22 deg. 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 (UO{sub 2} {yields} UO{sub 2+x}) occurred at approximately the same potential (-400 mV) at both temperatures. However, the conversion of U{sub V} to U{sub VI}, and hence to soluble UO{sub 2}{sup 2+}, 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 deg. C than at 22 deg. C ({>=} 350 mV)