The thermal expansion, density and molar volume of some binary borate glasses were measured before and after exposure to a
gamma-ray dose of 103 kGy. The expansion curves for all glasses, which were measured from room temperature to above the softening temperature,
displayed similar characteristics. Increase of the lead oxide content decreased the thermal coefficient of expansion, but
the effects of different alkali metal cations were shown to depend on their ionic radii. The various proposed mechanisms of
thermal expansion are dealt with. The experimental results could be explained by considering the bond strengths, the polarizing
powers of the different cations and the damage produced by radiation. The possible compaction of the structure due to irradiation
is also discussed.