BUILDING MATERIALS PHOTON ATTENUATION, NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATE

High concentrations of natural radionuclides in building materials result in high dose rate indoors due to radon and thoron exhalation and the γ-rays emitted from them. Among the natural radionuclides contained in building materials, most attention has been given to 226Ra due to 222Rn exhalation and the subsequent internal exposure. In external dose calculations due to building materials it is usually assumed that there exists radioactive equilibrium among the radionuclides of both the uranium and thorium series. In the case of the radionuclides of the uranium series it is assumed that there exists radioactive equilibrium among the long lived radionuclides 238U, 226Ra and 210Pb. The above assumption is seldom checked mainly because of the difficulties in the γ-spectroscopic determination of 238U and 210Pb which is possible only by using low-energy photons, where intense self-absorption of the photons inside the sample exists. In this case the count-rate during a γ-spectroscopic analysis is highly affected by the intense self-absorption of the photons. For the determination of radionuclides emitting low-energy photons a method has been developed which needs as input among others the linear attenuation coefficient μ for the analysed material. This paper presents:

1. Correlations in the form μ=f( ρ , E ) developed for the estimation of the linear attenuation coefficient μ(cm-1 ) as a function of the material packing density ρ (grcm-3 ) and the photon energy E (keV) for several materials of environmental importance, such as building materials.
2. Gamma-spectroscopic analysis techniques used for the determination of 238U, 226Ra, 210Pb, 232Th and 40K 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 reported one is based on the direct determination of 226Ra and 235U from the analysis of the multiplet photopeak at ~186keV.
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.