Natural radioactivity of materials used in industry and construction in Serbia

Four different kinds of materials (feldspar, gypsum, clay and kaolin) commonly used in building construction and industry in Serbia were analyzed for their natural radioactivity, using gamma spectrometry. The radium equivalent activity, Ra(eq), the absorbed dose rate, D, the annual effective dose, DE, and the external hazard index, H(ex), were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The radium equivalent activities calculated in all samples are lower than the maximum admissible value 370 Bq kg(-1) set in the UNSCEAR report.([1]) The absorbed dose rate in air was found to vary from 0.02 to 0.19 mu Gy h(-1). Considering the fact that the average gamma dose rate indoors in Europe is 0.07 mu Gy h(-1[2]), gamma dose rate calculated for feldspar, clay and kaolin samples exceed this limit. The obtained results for annual effective dose exceed limits of 0.41 mSv([1]) for feldspar, clay and kaolin samples. If the H(ex) exceeds unity, we might conclude that the potential external dose(s) to exposed individual(s) will exceed the acceptable level, and some action may be required. The obtained values of H(ex) are lower than unity for all investigated samples. All samples were measured immediately after preparation, except 10 samples of feldspar, because a comparative analysis were made between 215 samples which were measured immediately after preparation and 10 samples which were measured after radioactive equilibrium was reached in order to detect differences in the obtained concentrations.