Irradiation effects in simplified nuclear waste glasses

The structural evolution of simplified nuclear waste glasses under β-irradiation (2.5 MeV) has been studied up to cumulated doses of the order of 109 Gy. A rapid saturation of the point defect creation is observed at a very low level (in large contrast with what is observed on pure silica). At large doses, we also observe an increase of the polymerization of the vitreous lattice, and the appearance of dissolved molecular oxygen, which however does not coalesce into bubbles. These evolutions can be linked with the diffusion of alkaline ions in the material. The effects of the glass composition (mixed alkali effect, specific role of some particular cations, which are known to block the structural evolution) have been also investigated in order to study the possibility of decreasing alkaline mobility under irradiation.