Abstract
Disposal in deep geological layers is the main course of action envisaged in France for the management of high-level nuclear waste, the chemical immobilization of radionuclides being ensured by the use of borosilicate glass. Over time and as groundwater permeates through the waste package’s protective barriers, the glass matrix is expected to undergo chemical alteration. Simplified borosilicate glass alteration in the presence of water and self-irradiation (α, β, γ) from radionuclides has been an object of research for several decades, and it was established that energy deposition via self-irradiation increases the alteration rate and formation of an altered layer [1], [2]. The observed morphology of the altered glass layer features a structure of pores up to a few nms in diameter [2], [3], the long-term role of which is still unclear [4]. The closure of such pores under certain conditions was observed as well [5], suggesting that competing processes may be at work. Concomitantly, electron and ion irradiation of mesoporous silica such as SBA-15 and MCM41 was recently investigated, and the collapse of the pore structure was monitored using Small-Angle X-Ray Scattering (SAXS) [6], [7]. Here we propose a novel approach to the study of borosilicate glass alteration layers via the sol-gel synthesis of an appropriate mesoporous substitute, suitable for SAXS monitoring. Since the presence or absence of water is suspected to be a determining factor [5], an experimental setup is devised to provide a wet environment while irradiating the material. [1] C. Gillet, Etude des effets de synergie entre irradiation et altération par l’eau des verres nucléaires., UNIVERSITÉ DE MONTPELLIER, (2022). [2] M. Tribet et al., New Insights about the Importance of the Alteration Layer/Glass Interface, J. Phys. Chem. C, vol. 124 (2020), no 18, p. 10032. [3] S. Gin et al., A General Mechanism for Gel Layer Formation on Borosilicate Glass under Aqueous Corrosion, J. Phys. Chem. C, vol. 124 (2020), no 9, p. 5132. [4] M. Taron, Simulation à l’échelle nanoscopique du transport réactif : application à la dissolution des verres nucléaires , UNIVERSITÉ DE MONTPELLIER, (2022). [5] A. H. Mir, A. Jan, J.-M. Delaye, S. Donnelly, J. Hinks, et S. Gin, Effect of decades of corrosion on the microstructure of altered glasses and their radiation stability, Npj Mater. Degrad., vol. 4 (2020), no 1, p. 11. [6] J. Lin, Radiation-induced Alterations in Mesoporous Silicas: The Effect of Electronic Processes Involving Ions and Electrons, UNIVERSITÉ DE MONTPELLIER, (2022). [7] Y. Lou, B. Siboulet, S. Dourdain, M. R. Rafiuddin, X. Deschanels, et J.-M. Delaye, Molecular dynamics simulation of ballistic effects in mesoporous silica, J. Non-Cryst. Solids, vol. 549 (2020), p. 120346.