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High entropy alloys (HEAs) are promising materials for various applications including nuclear reactor environments. Thus, understanding their behavior under irradiation and exposure to different environments is important. Here, two sets of near-equiatomic CoCrCuFeNi thin films grown on either SiO2/Si or Si substrates were irradiated at room temperature with 11.5 MeV Au ions, providing similar behavior to exposure to inert versus corrosion environments. The film grown on SiO2 had relatively minimal change up to peak damage levels above 500 dpa, while the film grown on Si began intermixing at the substrate–film interface at peak doses of 0.1 dpa before transforming into a multi-silicide film at higher doses, all at room temperature with minimal thermal diffusion. The primary mechanism is radiation-enhanced diffusion via the inverse Kirkendall and solute drag effects. The results highlight how composition and environmental exposure affect the stability of HEAs under radiation and give insights into controlling these behaviors.

Characterizing oxide nuclear fuels is difficult due to complex fission products, which result from time-evolving system chemistry and extreme operating environments. Here, we report a machine learning-enhanced approach that accelerates the characterization of spent nuclear fuels and improves the accuracy of identifying nanophase fission products and bubbles. We apply this approach to commercial, high-burnup, irradiated light-water reactor fuels, demonstrating relationships between fission product precipitates and gases. We also gain understanding of the fission versus decay pathways of precipitates across the radius of a fuel pellet. An algorithm is provided for quantifying the chemical segregation of the fission products with respect to the high-burnup structure, which enhances our ability to process large amounts of microscopy data, including approaching the atomistic-scale. This may provide a faster route for achieving physics-based fuel performance modeling.

Pacific Northwest National Laboratory (PNNL) has leveraged focused ion beam capability at their Category II Nuclear Facility to facilitate nuclear materials analysis and experimentation at the micron scale. For this particular study, micron-size specimens of un-irradiated UO2 fuel pellets of various enrichments were prepared and irradiated to a burnup equivalent of 8–3700 MWd/MTU. This represents first of its kind study of used fuel investigations outside of a hot cell facility, dramatically minimizing resource requirements through reduction in scale. Results of this study provide insight into the initial production of noble metal phase particles in used nuclear fuel at extremely low burnup levels.

Cu90Ag10 alloys were subjected to severe plastic deformation at temperatures ranging from 25 to 400 °C and strain rates ranging from 0.1 to 6.25 s−1 using high-pressure torsion. The deformed samples were characterized by x-ray diffraction, transmission electron microscopy, and atom-probe tomography. A dynamic competition between shear-induced mixing and thermally activated decomposition led to the self-organization of the Cu–Ag system at length scales varying from a few atomic distances at room temperature to ≈50 nm at 400 °C. Steady-state microstructural length scales were minimally affected by varying the strain rate, although at 400 °C, the grain morphology did depend on strain-rate. Our results show that diffusion below 300 °C is dominated by nonequilibrium vacancies, and by comparison with previous Kinetic Monte Carlo simulations [D. Schwen et al., J. Mater. Res. 28, 2687–2693 (2013)], their concentration could be obtained.