The mixed alkali modified borosilicate base glass used in the vitrification of high level radioactive waste (HLW) has been mixed with various trivalent oxides to give a range of glass transition temperatures (Tg). The ultrasonic wave velocities in these samples have been measured from room temperature to 20 deg C above Tg using non-contact, laser based ultrasound. A pulsed Nd: YAG was used to generate ultrasound in the samples and ultrasonic detection was performed using a wide band Michelson interferometer. A sharp decrease in velocity is observed at temperatures in the region of the onset of glass transition as indicated by differential thermal analysis and dilatometry. This technique should allow the remote determination of the elastic properties of the glass and supercooled liquid at temperatures up to and above the liquidus.
