Abstract
For the handling of high level nuclear waste (HLW), new glass formulations with a high waste capacity and an enhanced thermal stability, chemical durability, and processability are under consideration. This study focuses on the durability of peraluminous glasses in the SiO2–Al2O3–B2O3–Na2O–CaO–La2O3 system, defined by an excess of Al3+ ions compared with the network-modifying cations Na+ and Ca2+. To qualify the behavior of such a peraluminous glass in a geological storage situation, its chemical durability was studied in various environments (pure water, groundwater, and alkaline solutions related to a cement environment) and glass alteration regimes (initial rate, residual rate, and resumption of alteration). The alteration solution was characterized by inductively coupled plasma, and the altered glass by scanning electron microscopy, X-ray diffraction and secondary ion mass spectrometry. A comparative study of the chemical durability of these and reference glasses (ISG and SON68) over all timescales highlights the remarkable properties of the former. While their initial dissolution rate is of the same order as the reference glasses, the gel formed under silica saturation conditions is more passivating, making its dissolution rate at least one order of magnitude lower, while its low alkalinity makes it less susceptible to clayey groundwater and highly alkaline solutions.
Highlights
In France, high level nuclear waste is currently immobilized inR7T7 borosilicate glass
Glass dissolution kinetics in contact with water begins by a release of alkaline elements, a process that is rapidly limited by the diffusion rate through the dealkalized glass layer.[21,22,23,24,25]
The dissolution rates calculated from boron release rates are given with the caveat that this element is partially retained in the altered layer
Summary
The resistance of glass to aqueous alteration is not an intrinsic property of the material, but is rather the response of glass to a range of environmental factors.[17,18,19,20] In a closed system, glass dissolution kinetics in contact with water begins by a release of alkaline elements, a process that is rapidly limited by the diffusion rate through the dealkalized glass layer.[21,22,23,24,25] At the same time, the hydrolysis of the glass network leads to the congruent release of the network-forming and -modifying elements This initial dissolution period (or Stage I), continues as long as there is no feedback effect of dissolved elements on the glass dissolution rate. Boron retention is approximately 30%, as reported previously by Molières et al.[48] for borosilicate glasses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
