Morphological evolution of alteration layers formed during nuclear glass alteration: new evidence of a gel as a diffusive barrier

• Published in: Journal of nuclear materials 2004-03, Vol.326 (1), p.9-18
• Main Authors: Rebiscoul, Diane, Van der Lee, Arie, Rieutord, Francois, Né, Frédéric, Spalla, Olivier, El-Mansouri, Abdeslam, Frugier, Pierre, Ayral, André, Gin, Stéphane
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical Sciences; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Installations for energy generation and conversion: thermal and electrical energy
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2003.10.015

This paper presents X-ray reflectometry and nitrogen adsorption results on alteration films formed at the surface of the French high level radioactive waste reference glass: SON68 glass (R7T7-type). For the first time, in situ (underwater) X-ray reflectometry has been used to investigate the alteration of this nuclear glass. A morphological evolution of alteration films is proposed and related to different steps of alteration kinetics. Initially a de-alkalinized glass layer is obtained, followed by the formation of a gel having an open porosity. Subsequently the gel densifies as the glass alteration rate decreases and finally the pore size increases upon formation of a dense and thin zone within the film. The latter dense zone within the gel could constitute a diffusive barrier. This hypothesis is also discussed for simplified glass gels.