Photon attenuation, natural radioactivity content and radon exhalation rate of building materials

High concentrations of natural radionuclides in building materials can result in high dose rates indoors, from both internal and external exposure. In dose calculations, the main radionuclides of interest are Ra-226, Th-232 and K-40. Usually much attention is paid to Ra-226 due to Rn-222 exhalation and the subsequent internal exposure. Other radionuclides of the uranium series such as U-238 and Pb-210, emitting low energy photons are not usually determined and an assumption of radioactive equilibrium is made. The above assumption is seldom checked mainly because of the difficulties in the gamma-spectroscopic analysis of low energy photons. For the determination of radionuclides emitting low-energy photons, in samples like building materials where intense self-absorption of the photons exists, a method for self-absorption correction has been developed. The method needs as input the linear attenuation coefficient mu for the material under analysis. This paper presents: 1. Correlations in the form mu=f(rho,E) developed for the estimation of the linear attenuation coefficient mu (cm(-1)), as a function of the material packing density rho (g cm(-3)) and the photon energy E (keV), for building materials as well as other materials of environmental importance. 2. Gamma-spectroscopic analysis techniques used for the determination of U-238, Ra-226, Pb-210, Th-232 and K-40 in environmental samples, together with the results obtained from the analysis of building materials used in Greece, and industrial by-products used for the production of building materials. Among the techniques used, one is based on the direct determination of Ra-226 and U-235 from the analysis of the multiplet photopeak at similar to186 keV. 3. Results from radon exhalation measurements of building materials such as cement and fly-ash and building structures conducted in the radon chambers in our Laboratory. Based on the above results, dosimetric calculations are also reported. (C) 2002 Elsevier Science Ltd. All rights reserved.