How does borosilicate glass, the material used to lock away high-level radioactive waste, hold up after not just months, but decades in water? Our new study, led by the University of Montpellier and the French Alternative Energies and Atomic Energy Commission (CEA, Marcoule) tracks a simplified glass (CJ2) from 7 days to 27 years and shows how a thin, self-forming “gel layer” on the surface gradually matures and slows further glass alteration.
“A simplified description of the different diffusive processes in the gel layer” from Narayanasamy, S., et al., npj Materials Degradation 9, 118 (2025). https://doi.org/10.1038/s41529-025-00664-w. Licensed under CC BY-NC-ND 4.0 (no modifications; non-commercial reuse).
What we found
As the glass meets water, it forms a porous, silica-rich gel. Over time, the gel’s pores coarsen and become less connected, which makes it harder for water and dissolved species, especially boron, to move. That reduced transport is the key reason the glass alteration rate keeps dropping with age. Techniques like cryo-TEM, SAXS, ToF-SIMS, and stable-isotope tracing (¹⁸O and ¹⁰B) let us watch this evolution and quantify the slow-down.
Who did what
The majority of the work was carried out by colleagues at Montpellier University and CEA (France), who led the long-duration experiments and advanced characterisations. To probe how the gel interacts with water, the water vapour adsorption measurements were performed at ZHAW (Switzerland) using the IGAsorp dynamic vapour adsorption equipment. These IGAsorp results reinforced the picture from microscopy and scattering: older gels have smoother, larger pores with lower connectivity, consistent with reduced diffusion through the layer.
Why it matters
By establishing the link between the long-term decay in alteration rate to measurable changes in gel transport properties, this work strengthens confidence in vitrification as a safe, durable strategy for immobilising nuclear waste over geological timescales, and gives modellers concrete handles (pore size, connectivity, diffusion) to predict performance further into the future.
Relevance to Aerospace: Water vapour adsorption
We quantified water uptake and transport using an IGASorp, a Dynamic Vapour Sorption (DVS) analyser, which measures isotherms and kinetics under tightly controlled humidity and temperature conditions. The same adsorption–diffusion toolkit applies directly to aerospace: moisture uptake in polymers and fibre-reinforced composites, validation of humidity sensors for low-RH cabins, and ECS (environmental control system) studies where cruise-cabin humidity is typically very low. These methods help quantify how materials and devices behave at the single-percent to 10% RH levels often seen in flight.
Reference
Please see our article referenced below and published in npj Materials Degradation:
Narayanasamy, S., Bell, J. G., Tiwari, S., Charpentier, T., Delaye, J.-M., Cournède, É., Thill, A., Taché, O., Lai-Kee-Him, J., Ancelin, A., Cabié, M., & Gin, S. (2025). Insights into gel maturation from alteration of borosilicate glass from 7 days to 27 years. npj Materials Degradation, 9, 118. https://doi.org/10.1038/s41529-025-00664-w