Mechanisms of Leaching and Dissolution of UO2Fuel

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Abstract
An integrated experimental approach to mechanistic studies of the leaching and dissolution of irradiated UO2fuel is described. The program includes an investigation of the solubility of the UO2 matrix under thermodynamically well-defined conditions, detailed measurements of the leaching and dissolution of irradiated fuel under simulated disposal conditions, and electrochemical measurements with a novel UO2 electrode to elucidate dissolution mechanisms. Initial experiments show that the solubility of UO2 under alkaline reducing conditions is relatively insensitive to temperature changes, that the leach rates of irradiated fuel are also not strongly temperature dependent, and that surface films on the UO2 fuel may play an important role in the dissolution process. Several aspects of the UO2 matrix dissolution process are now understood, and the approach taken has indicated where future work is needed.