Self-healing capacity of nuclear glass observed by NMR spectroscopy

9^th World Congress on Materials Science and Engineering

June 12-14, 2017 Rome, Italy

Thibault Charpentier

Universit�© Paris-Saclay, France

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Borosilicate glasses have been recognized as valuable materials for the conditioning of nuclear wastes. An important issue for their long-term behavior is radiation effects which may impact their performance and stability. To address these concerns, a fundamental understanding of the origin at the atomic scale of the macroscopic property evolutions must be established. To this aim, magic-angle spinning nuclear magnetic resonance (MAS NMR) has firmly established itself as one of the most powerful tool to investigate glass structure. Recently, using external heavy ions irradiation (Xe, Au and Kr) to simulate alpha decays, dramatic changes in the local network structure were evidenced: Conversion of tetrahedral BO4 units into planar trigonal BO3 units (11B), appearance of high-coordination aluminum units (AlO5, AlO6); glass depolymerization (29Si) and changes in the distribution of alkali cations (23Na). Additionally, the spectra broaden globally which supports the hypothesis of an increased topological disorder after irradiation. All these structural changes are similar to those observed with increasing the glass temperature or quenching rate and support therefore the model of ballistic disordering fast quenching events which induce a new glassy state with higher fictive temperature. Until recently, such studies were limited to externally irradiated samples (enabling the different components of irradiation to be dissociated for their precise investigation), but recently, the first MAS-NMR experiments could be performed on radioactive glasses (doped with 244Cm 0.1 % mol.) paving the way for future MAS NMR examinations of self-irradiation damages in glasses. Experiments were performed at the Joint Research Centre Institute for Transuranium Elements (JRC-ITU) where a commercial NMR spectrometer were integrated with a radioactive glovebox and a MAS commercial probe. First results will be presented. Competitive effects between the recoil nuclei and alpha decays were evidenced and the high resistance of the nuclear waste glasses corroborated.

Biography :

Email: thibault.charpentier@cea.fr