We have prepared a range of Advanced Gas-cooled Reactor (AGR) SIMFUELs at a range of simulated burn-ups and, using Raman spectroscopy, have studied the effect of the SIMFUEL dopants on the UO2 crystal structure. We have also studied the effect of exposure to hydrogen peroxide solutions on the SIMFUEL surface. The intensity of the fundamental U-O stretch (445 cm-1) decreases as the amount of dopant increases in each SIMFUEL burn-up composition. A simultaneous increase in the lattice damage (500 – 700 cm-1) peak is observed as the UO2 cubic fluorite lattice structure becomes more distressed and moves towards a tetragonal structure. Exposure to 100 µmol dm-3 H2O2 further decreases the fundamental U-O stretch and increases the lattice damage peak, suggesting that additional point defects are established as the concentration of interstitial oxygen is increased in the lattice via the H2O2-induced corrosion of the SIMFUEL.