On the Change in Physical Properities of Radiation Shielding Window Glass by Gamma Ray Irradiation

Abstract

As to the window glass for shielding the hot cave, its density, index and transmittance should not be affected by radiation. Tests are made with pieces of window glass: the density by a picnometer, the index by a spectrometer and the transmittance by a Beckman's automatic recording spectrophotometer. The total doses of γ radiation given to these test pieces are varied: 10⁶r, 3×10⁶r, 10⁷r, 3×10⁷r and 1.16×10⁸r with the dose rate of 4.0×10⁵r/hr at 17.5cm from a source of 10 kc Co⁶⁰. The result shows that the density and the index are not appreciably affected. As for the transmittance, medium density glass-non-brawing glass-undergoes a very slight change at a room temperature of 18°C with equally slight coloration. But high density glass is different: the transmittance is reduced great deal by coloration. The color, although fades in time, conspicuously at first, when the glass is left free from radiation effect, remains even after thirty days bringing in a serious problem concerning the quality of glass for shielding radiation. The cause of coloration and subsequent fading is discussed.