Jason Schulthess, a doctoral candidate in materials science and engineering, will defend their dissertation titled “Fabrication and Diffusion Bonding Performance in U-Mo Nuclear Fuel Plates.” Their advisor, Dr. Joesph Newkirk is a professor in nuclear engineering and radiation science. The dissertation abstract is provided below.

This work investigates the fabrication science, interfacial chemistry, microstructural evolution, and mechanical performance of AA6061 clad monolithic U Mo nuclear fuel plate assemblies, integrating thermodynamic modeling, advanced microscopy, mechanical testing across multiple length scales, historical process review, and machine learning. The research first establishes the mechanisms governing oxide disruption and metallic bond formation during hot isostatic pressing (HIP), showing that Mg in AA6061 reduces Al₂O₃ to MgO and participates in Mg₂Si precipitation, with cooling rate and bonding temperature strongly influencing precipitate coarsening and interfacial morphology. Experimental HIP campaigns confirm that MgO and Mg₂Si dominate interfacial chemistry, while precipitate size affects tensile elongation and anisotropic behavior relative to bond orientation. Micro tensile testing of irradiated Al/Zr and Zr/U Mo interfaces demonstrates that diffusion bonds remain mechanically robust—even stronger than bulk material—at intermediate irradiation doses, with failures occurring away from bond regions. A comprehensive review of decades of monolithic U Mo fuel fabrication reveals that fuel swelling is governed primarily by fission density rather than subtle process variations, though homogenization and Zr diffusion barriers remain essential for microstructural stability. Machine learning models, trained on multiscale mechanical datasets with enriched precipitate level features, successfully capture trends in strength and elongation, illustrating the predictive value of data driven approaches for complex joined systems.