Simultaneous Measurement of Radon and Thoron Released from Building Materials Used in Japan

Common building materials used in constructing dwellings are a major source of radon and thoron gases emanation into the indoor environment.Concentrations of the radionuclides 226 Ra and 232 Th and radon/thoron exhalation rates are important parameters for characterizing radon and thoron sources in building materials and comparing the relative contribution of different materials to the total radiation dose.In the present study, concentrations of the radionuclides 226 Ra, 232 Th and 40 K in different kinds of granite used as building materials in Japan were determined by γ-ray spectroscopy, and a common hazard index, the radium equivalent index, was evaluated on the basis of those results.Exhalation rates of radon and thoron were measured by using an accumulation chamber equipped with a solid-state alpha particle detector.The influence of chamber leakage and back diffusion time decay constants on radon exhalation rate was also estimated, and the correlations between radon/thoron exhalation rates and their parent nuclide (radium/thorium) concentrations were examined.