Measurements of Thorium and Uranium Concentrations in the Front Glass of CRT by the .GAMMA.-Ray Spectrometry and the Neutron Activation Analysis.

Concentrations of thorium and uranium are measured in the front glass of CRT (cathode ray tube) of television sets by the two methods of the γ-ray spectrometry and the neutron activation analysis. In the former method, measurements are made on an assumption of the radioactive equilibrium in the respective series of thorium and uranium. The concentrations obtained by the two different methods agree well within experimental uncertainties, showing the radioactive equilibrium in the present samples. It is found that the thorium and uranium concentrations in the glass can be measured by the γ-ray spectrometry as well as by the neutron activation analysis. Moreover, the concentrations of thorium are generally higher than those for uranium. This trend is consistent with that of the natural abundance for thorium and uranium in the earth's crust.