Apparent permeation rate of tritium through borosilicate glass

Abstract

Apparent permeation rates of tritium through borosilicate glasses were estimated from the volume of residual gases in ampules kept at room temperature for over 20 and 40 years. The permeation rates were 1.5 × 10⁻¹⁷ mol/m s Pa for 20-year-old borosilicate ampules and 7.0 × 10⁻¹⁸ mol/m s Pa for 40-year-old Pyrex glass ampules. These values are 1,500 times larger than the extrapolated value of H₂ permeation through fused silica. The typical decrease rate for a 30 cc ampule was 7 × 10⁻⁹ s⁻¹, which was 4 times higher than the decay rate of tritium (1.787 × 10⁻⁹ s⁻¹). The apparent permeation in this report includes permeation through the ample wall and the formation of OT in the ample wall.