Topical report on solid analyses performed on altered glass samples from tests described in RS SCK-15-HLW-03

This report presents in detail the results of Scanning Electron Microscopy–Energy Dispersive X-Ray spectroscopy (SEM-EDX) and X-Ray Diffraction (XRD) analyses that were carried out on altered glasses SON68, ISG and SM513 from tests described in the Research Specification SCK-15-HLW-03, Leaching tests (continuation of leach tests from program 2009-2014). The solution analyses of these tests were previously described in report SCK•CEN-ER-286. The analyses showed that the tendency to form alteration layers increases with pH, which is related to the cement water composition (Old Cement Water (OCW) <Evolved Cement Water (ECW) <Young Cement water with Ca (YCWCa)) and with temperature (30 °C <70 °C). In OCW, no significant layer formation was observed. In ECW, the glass powders showed an alteration layer, but the glass monoliths did not. In YCWCa, all samples formed layers, except the SON68 monolith altered at 30 °C. The differences between monoliths and powders may be due to the loss of layers for the monoliths, or differences in local alteration conditions. In YCWCa, layer thicknesses ranging from 2 to 30 μm were observed. The alteration layers were characterized either as alkali-silica gels or Calcium Silicate Hydrates. In YCWCa at 70 °C, the XRD analyses suggest formation of crystalline phases such as phillipsite, zeolite P1, calcite and silicon oxide.