NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATES OF GREEK BUILDING MATERIALS

Greek building materials were analysed for natural radioactivity (Ra-226, Th-232 and K-40) which, according to the results obtained, is low with the exception of a few specimens of cement and clay bricks with Ra-226 concentrations up to 147 and 48 Bq/kg respectively. The radon exhalation rate of the same materials has been evaluated using an air-tight 1m³ steel container. The container environment is conditioned by a heating unit and a humidifier, in order to control temperature and humidity over the range 12-45 °C and 15-99% respectively. A ±50 mbar differential pressure transducer is used for recording pressure changes inside the container, which is also equipped with an aerosol generating system. Radon progeny radiation is continuously monitored in-situ via a 2x2'' Am-doped NaI detector stabilised for spectrum shifts. Furthermore, grab sampling on high efficiency filters analysed using high-resolution gamma and alpha spectrometry is also conducted. The exhalation rate of the above Greek building materials already analysed range between 3-20 ?Bq/(kgs). Moreover, brick walls and concrete slabs constructed using these materials present exhalation rates between 2-3 mBq/(m²s).