Structural understanding of the α auto-irradiation effects in glasses, coupling between spectroscopic studies and atomistic modelling

In order to understand the aging under irradiation of nuclear glasses, the alterations (at the atomic scale) induced by an internal irradiation (244Cm) or an external irradiation (Au, Si, He or Kr) of simplified glasses (SiO2, B2O3, Na2O, ZrO2, CaO) similar to the industrial glass R7T7 have been observed. In this study, three ways are developed: 1)by internal irradiation: use of actinides with short periods to reach in little time alpha decay doses equivalent to the doses received by the storage glasses in several ten thousands years; 2)by external irradiation: irradiation by heavy or light ions in order to simulate the different components of the α decay (α particles, recoil nucleus); 3)by molecular dynamics method: accumulation of displacements cascades to reproduce the effects of the doses induced specifically by the recoil nucleus. Structural analyses (X diffusion, Raman, 17O, 29Si, 23Na, 11B NMR, EXAFS, XANES) of macroscopic properties (density, hardness, elastic constants) on glasses irradiated and modelled will be carried out and will allow to describe the evolution of the structure under irradiation (structure factors, local entities (reedmergnerite, danburite...), coordination number of the species, size of the rings...) and to propose an explaining at the atomic scale of the effects macroscopically detected. First experimental results are given. (O.M.)