MEASUREMENTS OF NATURAL RADIOACTIVITY IN GREEK BUILDING MATERIALS

Building materials and paints may release radon or cause direct radiation exposure because of their content of radium, thorium and potassium. Concrete, brick and granite-stone walls may produce significant external dose rates nGy/hr and -furthermore- give rise to radon exhalation rates of up to 50 Bq/m². A wide research project to investigate the radioactive behaviour of Greek building materials and structural modules has been set-up and is still in progress. In the framework of this project ample specimens of commonly used building materials have been collected randomly over the country. The specimens were dried under ambient temperature and then pulverised to less than 90 ?m; finally, the water content of all specimens was determined before being hermetically sealed in 0.282 L cylindrical plastic boxes, covered with a film of epoxy resin to limit - as far as possible - escape of radon. Each box was analysed after secular equilibrium of Ra-226 and Th-232 with their decay products was obtained, using high resolution Ge-detectors setups; activity concentrations were averaged from photopeaks at several energies. The results obtained show that the natural radioactivity content of the various Greek building materials examined is very low. Only a few specimens of cement and clay bricks present a rather high Ra-226 concentration up to 144 and 48 Bq/kg respectively. However, these values are within the range of similar materials used in other European countries.