As the lightest metal structural materials, magnesium (Mg) alloys offer extensive application potential. Gadolinium (Gd), as the primary alloying element in Mg alloys and recognized for its notable thermal neutron capture cross-section, is considered one of the most efficient neutron absorbers. Thus, the Mg–Gd alloy is highly expected to emerge as a material with remarkable neutron absorption capacity. Hence, in this study, the thermal neutron-shielding capabilities of Mg–Gd alloys were comprehensively examined by fabricating four as-cast Mg– x Gd alloys with varying compositions ( x = 0, 5, 10, and 15 wt%). The obtained results were further corroborated by sophisticated modeling and calculations using SuperMC. The results revealed a direct correlation between the thermal neutron absorption capacity of the Mg–Gd alloys and the increase in Gd content, with a noteworthy neutron attenuation factor of 22.33. Moreover, in an Au ion irradiation experiment conducted at 200°C, the Mg–15Gd alloy exhibited exceptional radiation resistance, with a displacement per atom (dpa) of 10. The matrix and second-phase regions were devoid of any cavity formation. Instead, a finite number of dislocation rings were observed, forming both leaf-like and granular Gd-rich nanoscale precipitates. This study underscores the versatility of Mg–Gd alloys as efficient neutron shielding materials and structural materials tailored for applications demanding radiation resistance in diverse environments.

U₃Si₂ is a potential accident-tolerant fuel (ATF) due to its high thermal conductivity and uranium density relative to UO₂. The grain size and distribution play an essential role in the service performance of U₃Si₂. However, the grain evolution is quite complicated and remains unclear, which limits further application of U₃Si₂ in the ATF assembly. In the present work, a phase-field model is employed to investigate the nucleation and growth of grains in U₃Si_2. Our results show that the number of grains rises rapidly at the nucleation stage until they occupy the whole system. After that, the grain radius and area continue to grow, and the grain number decays. The grain area increases in time according to the linear law, while the mean grain radius increases with time in a power law form with the scaling growth exponent z = 0.42, which is quite close to the theoretically predicted value. Finally, we performed statistical analysis and found that the grain size evolution of U₃Si₂ obeys Rayleigh distribution. Our simulation not only elucidates the nucleation and evolution of grains in U₃Si₂ during the thermal treatment process unambiguously but also provides a fundamental study on the investigation of grain growth, subdivision, and even amorphization in the irradiated condition, which is very important for U₃Si₂ used as ATF in the light water reactor.

Due to the superior thermal conductivity and high uranium density, U₃Si₂ is an excellent candidate for conventional UO₂ nuclear fuel and shows great potential application in accident-tolerant fuel (ATF) assembly of light water reactors (LWRs). Currently, the behavior of Xe bubbles with internal or applied stress is rarely investigated, restricting further understanding of swelling in U₃Si₂. The mesoscopic phase-field method has been developed in this work to study the spatial and temporal Xe bubble evolution in U₃Si₂. The results show that the bubble density and its average size increase as the fission rate increases. Applied stress accelerates the nucleation and growth of gas bubbles, reshaping the bubbles’ morphology from spherical in a stress-free state into elongated along the applied direction in a stressed state. The gas bubbles in a local dislocation stress field nucleate preferentially at stress-concentrated sites and spread over the whole system in succession, and the bubble coarsening is controlled by the stress overlap of the dislocation pair. The results show a practical phase-field method for Xe bubble evolution study in U₃Si_2, which can be expanded into swelling behavior investigation in other fuels and lay a solid foundation for the development of ATF assembly.

The microstructure evolutions of cascade annealing in α-Zr crystals at $T=300\mathrm{K}$, 400 K, and 500 K for energy of 2, 6 and 10 keV with initially driving directions $⟨0001⟩$ and $⟨01\overline{1}0⟩$ of the primary knocked atoms are investigated by using molecular dynamics simulations. The results show that the relaxation time (τ_r) of cascades can play the role of an effective parameter for describing radiation damages during molecular dynamics simulations. τ_r of cascade with the larger surface area but with the same volume is much smaller, which promotes faster recombination of defects during cascade annealing. Energy is a crucial factor in the formation of cascade displacements of atoms and appearing of defects compared with temperature and direction of movement for initially knocking atoms.