During reactor irradiation, fuel pellets undergo a partial evolution of their microstructure. At high levels of burnup, a subdivision of grains into smaller grains in the peripheral areas of the fuel pellets - called high burn-up structure (HBS) - is observed. Similar changes also occur in the central regions of the pellets at elevated temperatures. These evolutions result from the combination of several factors, including the loss of energy from fission products. The effect of this damage could vary depending on the crystal orientation and grain size.
The main objective is therefore to understand how crystal orientation and grain size influence the damage caused by irradiation. Ion irradiation experiments will be conducted on single- and poly-crystalline UO2 samples at the JANNUS Saclay facility. In situ and ex situ characterizations using Raman and Rutherford backscattering (RBS-C) spectroscopy, transmission and scanning electron microscopy with Electron backscatter diffraction (EBSD) will be carried out.