Abstract The structural modifications induced by external β-irradiation have been investigated to simulate the ageing processes of nuclear glasses under irradiation. Six glasses in the CaO–Al 2O 3–SiO 2 system, from 10 to 68 mol% of SiO 2 content, were irradiated with electrons generated by a Van de Graaf accelerator. The structure of these glasses was studied using Raman and X-ray absorption spectroscopies at the Al K-edge. We observe that a band appears at 1557 cm −1 in the Raman spectra of irradiated glasses, which is assigned to molecular O 2, and that the average Si–O–Si bond angle decreases. An increase of the polymerization of the network is also detected in the Raman spectra of irradiated samples, which corresponds to a shift of the 1100 cm −1 band towards higher frequencies. This change in network polymerization is confirmed by an increase in the intensity of the main resonance at 1565 eV in the X-ray absorption spectra at the Al K-edge.