Natural radioactivity in building materials in Iran

This work presents a comprehensive study of natural radioactivity in building materials used in Iran. For this purpose, 177 samples of five types of building material, i.e. cement, gypsum, cement blocks, gravel and brick, were gathered from different regions of the country and analyzed by gamma spectroscopy to quantify radioactivity concentrations using a high purity germanium (HPGe) detector and a spectroscopy system. According to the results of this investigation, cement samples had maximum values of the mean Ra-226 and Th-232 concentrations, 39.6 and 28.9 Bq/kg, respectively, while the lowest value for mean concentration of these two radionuclides were found in gypsum samples 8.1 and 2.2 Bq/kg, respectively. The highest (851.4 Bq/kg) and lowest (116.2 Bq/kg) value of K-40 mean concentration were found in brick and gypsum samples, respectively. The absorbed dose rate and the annual effective dose were also calculated from the radioactivity content of the radionuclides. The results show that the maximum values of dose rate and annual effective dose equivalent were 53.72 nGy/h and 0.37 mSv/y in brick samples. The radium equivalent activities Req calculated were below the permissible level of 370 Bq/kg for all building materials. The values of hazard indexes were below the recommended levels, therefore, it is concluded that the buildings constructed from such materials are safe for the inhabitants. The results of this study are consistent with the results of other investigations in different parts of the world. (authors)