1.1 ,The vapor hydration test method can be used to study the corrosion of a waste forms such as glasses and glass ceramics2 upon exposure to water vapor at elevated temperatures. In addition, the alteration phases that form can be used as indicators of those phases that may form under repository conditions. These tests, which allow altering of glass at high surface area to solution volume ratio, provide useful information regarding the alteration phases that are formed, the disposition of radioactive and hazardous components, and the alteration kinetics under the specific test conditions. This information may be used in performance assessment (McGrail et al, 2002 (1)3 for example).