Measurement of the activity concentration of radionuclides (238U, 232Th, 226Ra, 222Rn ve 40K) naturally occurring in building materials used in kastamonu and radon mass exhalation rates of these building materials

Abstract: The natural radionuclides contained in building materials originating from earth's crust are radioactive sources that cause internal and external irradiation of individuals. Gamma radiation emitted from these radionuclides causes external irradiation and radon (222Rn) gas and its short half-life decay products are released from these materials and taken by the respiratory tract cause internal irradiation. Therefore, the knowledge of the level of natural radioactivity in building materials is very important for evaluating the external and internal radiation exposure to individuals. In this study, the activity concentrations of uranium (238U), thorium (232Th), radium (226Ra) and potassium (40K) in some building materials collected from Kastamonu province were determined by using gamma-ray spectrometry with a high purity germanium detector (HPGe). The minimum and maximum value of the activity concentrations of 238U, 232Th, 226Ra and 40K were found as 6.7±0.4 (plaster)-128.6±3.7 (brick), 2.6±0.8 (gypsum)-172.2±7.6 (granite), 5.2±0.6 (satin plaster)-187.0±2.4 (granite), and 12.3±17.0 (sand)-1958.0±83.4 Bq/kg (brick), respectively. Building materials are also a secondary source of radon in indoor environments such as homes, school and work places. Long-term exposure to radon and its short-lived decay products increase the risk of the lung cancer. Therefore, it is important to know of the radon concentration and radon exhalation rates (surface and mass) from building materials from point of the view of the understanding the individual contribution of each material to the total indoor radon exposure. In the study, the radon activity concentration, radon surface and mass exhalation rates from some building materials from Kastamonu were measured by the active method using a continuous active radon monitoring system (AlphaGUARD PQ2000 PRO) and compared with data in the literature. Radon surface and mass exhalation rates were found in the range of 2.9 (marble)-2734.6 mBq/m2.h (granite) and 0.033 (marble)-53.866 mBq/kg.h (granite), respectively. Radium equivalent activity index, activity concentration index, alpha index, indoor absorbed gamma-ray dose rate and the corresponding annual effective radiation dose, lifetime cancer risk were estimated to evaluate the radiation dose to individuals and usage of building materials from a radiological point of view and the results were compared with criteria or limit values. The results indicated that the examined samples used as building materials would not cause any significant radiological risk. Key Words: Building materials, radioactivity, gamma-ray spectrometer, radon, radon exhalation rate, annual effective radiation dose, lifetime cancer risk