Contribution of zeolite-seeded experiments to the understanding of glass resumption of alteration

M. Fournier (1) , S. Gin (1) , P. Frugier (1) , S. Depierre (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

Understanding the origin and the consequences of glass alteration regimes is necessary for the prediction of nuclear glass durability. The so-called “stage 3” or “resumption of alteration regime” of glasses used to sequester nuclear waste by vitrification, is characterized by a sudden acceleration of glass alteration rate arising from the precipitation of secondary minerals, mainly zeolites. To study this process, a promising approach is developed, based on seeding by synthesized zeolite seeds. This study quantitatively links the alteration of a six-oxide reference borosilicate glass (ISG) and the precipitation of zeolites that affects concentrations of key species—in particular aluminum—and thus the glass dissolution rate. The characterization of stage 3—easier at alkaline pH—can now be extended to pH conditions more representative of those found in a geological repository thanks to seeding that reduces, or even eliminates, the latency period preceding a resumption of glass alteration. The resumption occurrence and glass dissolution rate are related with temperature and pH. This study shows that the detrimental effect of zeolite precipitation decreases with decreasing pH and temperature, until it is no longer detectable at a pH around 9 imposed by the dissolution of the ISG glass. Even for both high temperature and high pH, the resumption rate is lower than the initial alteration rate, which remains the fastest kinetic regime

Mots clés: nuclear glass; long term behavior; ISG glass; resumption of alteration; stage 3; zeolites; seeding

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

M. Fournier, S. Gin, P. Frugier, S. Depierre. Contribution of zeolite-seeded experiments to the understanding of glass resumption of alteration. npj Materials Degradation, 2017, 1, pp.17. ⟨10.1038/s41529-017-0018-x⟩. ⟨cea-02418695⟩