Alteration of synthetic basaltic glass in silica saturated conditions: Analogy with nuclear glass
Résumé
This study investigates the analogy between basaltic and borosilicate glasses of nuclear interest, by focusing on
mechanisms controlling glass dissolution under silica saturation conditions. These conditions are representative
of a non- or slowly renewed contacting solution, favouring the formation of a potentially passivating silica rich
gel layer and secondary phases. Laboratory batch experiments were performed with synthetic basaltic glass
altered at 90 °C, at pH 7 in a saturated 29Si-doped aqueous solution for more than 600 days. Using elemental and
isotopic solution analysis and solid characterizations by SEM, TEM and ToF-SIMS, we show that basaltic glass
corrodes at an unexpectedly high and constant dissolution rate of 4×10−3gm−2 d−1 associated with the
absence of passivating gel. Our results highlight the fact that the dissolution rate is controlled by the hydrolysis
of the glassy network, sustained by the precipitation of clay-type minerals and amorphous silica. When tested in
similar conditions, the International Simple Glass (ISG), a six oxide borosilicate glasses of nuclear interest displays
a much lower rate limited by water diffusion through a passivating layer. The different behavior of the two
glasses is explained by their ability to form secondary crystalline phases at the expense of an amorphous passivating
film.
Domaines
Chimie
Origine : Fichiers produits par l'(les) auteur(s)
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