The hydration alteration of a commercial nuclear waste glass

Abstract The alteration of the commercial nuclear waste glass, PNL 76-68 , in a saturated water-vapor atmosphere at 260°C was investigated. The alteration products were identified using Raman microprobe spectroscopy, X-ray diffraction and scanning electron microscopy with associated energy-dispersive spectroscopy, and include a pyroxene of composition (Na 0.7 Ca 0.3 )(Fe 0.6 Zn 0.2 Ti 0.1 Al 0.1 )Si 2 O 6 , a zeolite belonging to the analcime-polucite series, an unidentified mineral, or two-phase intergroup, containing Ca, P and Si, and an amorphous surface depleted in Na, Ca, Al and Si. This alteration process is dependent on the glass composition, both regarding the alteration products that form and the rate at which they form. The ramifications to nuclear waste management are, that under conditions that could exist in a waste repository, PNL 76-68 glass alters to a more stable form, and this alteration could affect eventual nuclide release.