Structural evolutions of a borosilicate glass induced by heavy ions

High-level nuclear waste containment glass is subjected to irradiation-induced stresses whose consequences must be assessed to guarantee the material behavior over time. Alpha decay from the minor actinides confined in the glass structure is responsible for most of the atom displacements. Radiation studies of nuclear glasses have shown some slight evolutions of some macroscopic properties (density, mechanical properties). The understanding of the structural origin of these modifications is important for the modeling of the long term behavior of such materials. A powder of simplified borosilicate glass composition was irradiated by multi energies gold ions to simulate the effect of alpha decay. The irradiation conditions were defined to induce a constant nuclear interaction in the grains of diameter around 2µm. For these irradiations conditions, the hardness of the glass decreased by 35%. Structural characterizations of the pristine and irradiated powders were made by multinuclear (11B, 23Na, 27Al, 29Si) Magic Angle Spinning Nuclear magnetic Resonance (NMR) and RPE to try to identify the structural origins of the macroscopic modification observed. It is observed that the local environment of boron and sodium are highly influenced by the irradiation with an important increase of boron tri-coordinated and a significant modification of the sodium cations organization. The NMR silicon spectra show fewer evolutions but a slight shift is observed that may indicate a less polymerized silicate networ