Physical properties of U3Si2 with non-magnetic, ferromagnetic, and anti-ferromagnetic structures are predicted using DFT + U with Hubbard-U values from 0 to 4 eV. The stability of U3Si2 is compared with its neighboring phases, U3Si and USi. The results emphasize the importance of magnetism. For nonmagnetic U3Si2 a very large Hubbard-U value is required to accurately reproduce the physical constants. However, from the electronic structure of the studied magnetic states with different Hubbard-U values, it is clear that it is incorrect to use a non-magnetic model for paramagnetic U3Si2 because of the resulting nearly zero occupation of f-electrons.

Uranium silicide, U3Si2, is considered as an advanced nuclear fuel for commercial light water reactors with improved accident tolerance as well as competitive economics. Nd is employed as a local burnup indicator for conventional oxide fuels due, among other reasons, to its low mobility in the UO2 fuel matrix and its high fission product yield. As part of the studies necessary to determine whether Nd can be considered as a candidate burnup indicator in the U3Si2 concept fuel, we investigate the mobility of Nd in U3Si2. In this work, density functional theory (DFT) calculations are performed to predict the most stable accommodation sites of Nd in U3Si2, found to be within the uranium sublattice. Based on DFT calculations of binding energies and migration activation energies, we investigate Nd diffusion by computing the transport coefficients within the framework of the self-consistent mean-field method. Our calculations predict that the diffusion ratio of Nd to U is smaller in U3Si2 than in UO2. Moreover, at the individual maximum centerline temperature of the fuel, the diffusion of Nd in U3Si2 is much slower than in UO2. From this perspective, Nd represents a good candidate burnup indicator, in similarity to that in UO2.

In this study, the process involved in the fabrication of a potential accident tolerant fuel is described. Homogeneous uranium nitride microspheres doped with different thorium content were successfully manufactured using an internal gelation process followed by carbothermic reduction, and nitridation. Elemental analysis of the materials showed low carbon and oxygen content, the two major impurities found in the products of carbothermic reduction. Uranium nitride microspheres were pressed and sintered using spark plasma sintering (SPS) to produce pellets with variable density. Final density can be tailored by choosing the sintering temperature, pressure and time. Density values of 77–98% of theoretical density (%TD) were found. As expected, higher temperatures and pressures resulted in a denser material. Furthermore, a direct correlation between the onset sintering temperature and thorium content in the materials was observed. The change of onset temperature has been related to an increment in the activation energy for self-diffusion due to the substitution of uranium atoms by thorium in the crystal structure.

The present work studied the inter- and transgranular fracture properties in UO₂ based on density functional theory(DFT) calculations. An excess energy assessment approach was employed to calculate the traction-separation curves. The results show that the lattice has higher toughness than GBs in UO₂, consistent with the experimental observations. The impact of fission products (FPs) Xe and Mo on the fracture of UO 2 were also studied in the same methodology. The accommodation of FPs weakens both lattice and grain boundaries, and Xe has a more profound effect than Mo.