Estimating natural radiation exposure from building materials used in Sri Lanka

In this work, the natural radioactivity levels of several building materials used in Sri Lanka, were determined in terms of Bq kg(-1), and to calculate the radiological effects caused by this radioactivity. Activity concentrations of Ra-226, Th-232 and K-40 in eighteen samples of manufactured building materials were measured using gamma spectroscopy based on high purity germanium detector with an efficiency of 48% at 1332.5 keV. The measurement of the activity concentration in building materials is required to estimate the excess dose to public dwelling in such buildings. BEGe detector is a well-chosen equipment for this purpose. The activity concentrations for Ra-226, Th-232 and K-40 from the selected building materials ranged from (5.0 +/- 0.5 to 45.2 +/- 2.9 Bq kg(-1)), (7.1 +/- 0.6 to 68 +/- 5.9 Bq kg(-1)) and (42.8 +/- 3.8 to 1773 +/- 54 Bq kg(-1)) respectively. Radium equivalent activities, absorbed dose rate, the value of external hazard indexes and alpha indexes were calculated for the measured samples to assess the radiation hazards arising from using those materials in the construction of dwellings. The average value of indoor annual effective doses of Sri Lankan building materials was 0.22 mSv. Also the average value of outdoor annual effective doses of Sri Lankan building material was 0.05 mSv. It has been noted that the values of annual effective dose of Sri Lankan building materials were below the world average value of terrestrial annual radiation exposure which was 0.48 mSv. Therefore, the types used in the current study are quite safe to be used as building materials.