Measurement of the natural radioactivity in building materials used in Ankara andassessment of external doses

Abstract

A total of 183 samples of 20 different commonly used structural and covering buildingmaterials were collected from housing and other building construction sites and fromsuppliers in Ankara to measure the natural radioactivity due to the presence of226Ra,232Th and 40K. The measurements were carried out using gamma-ray spectrometry with two HPGedetectors. The specific activities of the different building materials studied varied from0.5 ± 0.1 to144.9 ± 4.9 Bq kg−1,0.6 ± 0.2 to169.9 ± 6.6 Bq kg−1 and 2.0 ± 0.1 to 1792.3 ± 60.8 Bq kg−1 for 226Ra, 232Th and 40K, respectively. The results show that the lowest mean values of the specific activity of226Ra, 232Th and 40K are 0.8 ± 0.5, 0.9 ± 0.4 and 4.1 ± 1.4 Bq kg−1, respectively, measured in travertine tile while the highest meanvalues of the specific activity of the same radionuclides are78.5 ± 18.1 (ceramic walltile), 77.4 ± 53.0 (granitetile) and 923.4 ± 161.0 (white brick), respectively. The radium equivalent activity(Raeq), the gamma-index, the indoor absorbed dose rate and the corresponding annual effectivedose were evaluated to assess the potential radiological hazard associated with thesebuilding materials. The mean values of the gamma-index and the estimated annual effectivedose due to external gamma radiation inside the room for structural building materialsranged from 0.15 to 0.89 and 0.2 to 1.1 mSv, respectively. Applying criteria recentlyrecommended for building materials in the literature, four materials meet theexemption annual dose criterion of 0.3 mSv, five materials meet the annual dose limitof 1 mSv and only one material slightly exceeds this limit. The mean values ofthe gamma-index for all building materials were lower than the upper limit of1.