The formation and chemical fractionation of the noble metal phase particles (also known as five-metal or “epsilon” phase particles) from nuclear fuel under irradiation is a process that is not well understood. These particles have been linked to many important phenomena over the life cycle of nuclear fuel, from in-reactor operations to long-term spent fuel disposition. In order to elucidate the physical and chemical mechanisms that govern the formation of these inclusions, we have studied these particles under various conditions. We have made the first direct observations of noble metal phase fission product agglomerates and gaseous xenon within the Fuel Cladding Interaction (FCI) zone of a high-burnup UO<sub>2</sub> fuel. We report elemental and isotopic analysis for the phase. Combining these results with microscopy, we have discovered a significant sixth component of these materials as well as observing two separate phases within the particles. In addition to in-situ microscopy analysis and a full isotopic analysis, we performed fresh micro-scale irradiations. These provided insight into the initial production of the noble metal phase particles at extremely low burnup levels.

New insights into the formation and transport mechanisms of noble metal particles in irradiated oxide fuel

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.