Characterization of the surface of the HLW glass R7T7 reacted in Salt Brines

Borosilicate glasses are proposed as waste form for the final disposal of High Level Waste in salt formations by the Federal Republic of Germany. To check the safety of this waste form the corrosion of the non-radioactive borosilicate glass R7T7 in salt brines has been studied in collaboration with the Hahn-Meitner-Institut, Berlin. Temperatures up to 190 degree C and S/V ratios (surface area to solution volume ratio) between 3.3 and 1000m Exp-1 were applied. S/V was varied by the addition of glass powder. The results presented here concern the characterization of the surface composition of the corroded glass (corroded at 190 degree C in a brine containing high amounts of MgCl2, called Q brine in this paper after removing the reaction product layer. The corrosion conditions were chosen to obtain samples typical of long term (silica saturation) corrosion. The surface composition was analyzed quantitatively by X-ray photoelectron spectroscopy by using externalstandard glasses with a comp osition similar to R7T7. Additionally scanning electron microscopy was employed.