Lattice parameter evolution of single doped and co-doped UO2 systems

The sinterability of chromia and gadolinia containing fuel pellets enabled an interpretation to be made of the possible atomic structure of the system. The percent theoretical density, lattice parameter and dopant solubility of the binary systems U1-xCrxO2 and U1-xGdxO2, as well as the tertiary system U1-x-yGdxCryO2, was analyzed. The distribution of dopant across the fuel pellets was investigated by electron microprobe analysis (EPMA). The lattice parameter was acquired by X-ray powder diffraction (XRD) and calculated using the unit cell refinement method. This data allowed us to expand the lattice contraction in function of the dopant concentration. The theoretical density was calculated and compared with that of pure UO2. A scoping study of the fuel doping methodology was performed on the U1-xCexO2 system. Microstructure analysis was done using XRD and SEM-EDS, similar to the procedure above. This allowed us to determine a good doping method, which can be further elaborated in the future.