238Pu-doped UO2 was characterised periodically to investigate the long-term effects of α-self-irradiation on spent nuclear fuel. Samples of two compositions (1.25 and 5% wt 238Pu), were studied by means of X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The cumulated dose received by the samples was measured in displacements per atom (dpa) to allow comparison between the two samples and to the literature values. XRD characterization showed that the lattice swelling approached saturation at 0.3% of the lattice parameter of the cubic cell at 0.4 dpa damage accumulation. Microstrain decreased for the whole duration of the study, as a result of point defect recombination into dislocation loops that were observed by TEM for dpa as low as 0.072. Raman highlighted the broadening of the T2g band and the increase and broadening of the defect triplet band. Both batches of samples followed the same trend if plotted against dpa, proving that for these dopant concentrations the self-irradiation effects do not depend on the rate of radiation damage creation in the matrix.