HELIUM AND DEUTERIUM MIGRATION IN ALKALI SILICATE-GLASSES

The permeability, diffusivity and solubility of helium and deuterium h ave been measured for all five alkali silicate binary systems. The hel ium permeabilities of potassium, rubidium and caesium silicate glasses are essentially identical for glasses having identical molar composit ions. The deuterium permeability at 200-degrees-C of these glasses is a factor of approximately 50 less than that of helium. This behaviour is very different from that found for alkali borate and germanate glas ses. The effect of phase separation on the helium permeability of lith ium silicate glasses is reported in greater detail than in previous wo rk.