Behavior of helium release from simulated radioactive waste glasses

Rates of He release from two kinds of simulated high-level radioactive waste glasses were measured in the temperature range from 573 to 753K by a mass spectrometric method. Diffusion coefficients of He in the glasses were determined from the fractional release data. The diffusion coefficients were given as a function of temperature by the equations: D/(m²·s^-1) = 2.3 × 10^-6 exp (-71.1±2.1 kJ/RT) for P0798 glass =9.8 × 10^-7 exp (-60.2±2.1 kJ/RT) for P0504 glass. In addition, solubilities of He in the glasses were determined from the measurement of the total amount of released He and found to be S/(atoms/m³) = 2.0 × 10²² for P0798 glass = 2.2 × 10²² for P0504 glass. at 693 K and 1.7 × 10⁵ Pa He. The diffusivities and solubilities of He in the glasses were, respectively, several and an order of magnitude lower than silica, alkali silicate and Pyrex glasses, which properties are notable for the radioactive waste glasses.