Radiation Behavior of Vitreous Silica

Several properties of vitreous silica relevant to application as an optical element in a reactor were studied, including density, refractive index, optical path, stress relaxation, and optical absorption. The irradiations were in fields characteristic of the fuel regions of several operating reactors and at temperatures up to 370°C. The radiation-induced changes in optical path are significant, but are much smaller than those in the density and refractive index because the last two are of opposite sign. The thermal coefficient of optical path causes changes of comparable magnitude. Optical absorption is not a serious matter in the upper end of the visible region.