Determination of natural radioctivity at phosphogypsum

Phosphate fertilizers are produced by the reaction of sulphuric acid with pulverized phosphate rock which contains naturally occurring radionuclides of the uranium-radium, and thorium series and radioactive potassium. Phosphogypsum are derived from the process production of phosphoric acid as a by-product or waste. The growing production of phosphogypsum has long caused on environmental and radiological problems with technological and economic effects in the phosphate industry in Turkey. These problems become inevitable to the implementation of various alternative in which phosphogypsums are utilized as a building raw materials. The aim of this study is to measure the activity concentrations of 226Ra, 232Th and 40K radionuclides in phosphogypsum samples obtained from Mersin and Bandırma fertilizer factories by using gamma spectrometric technique and to assess the radiological impacts from the utilization of phosphogypsum samples examined as a building raw material. The activity concentrations of 226Ra, 232Th and 40K measured in phosphogypsums samples and tabulated for each fertilizer factory were found as 250.8 Bq/kg, 14.6 Bq/kg and 10.1 Bq/kg for Mersin Fertilizer Factory (MFF) and 826.6 Bq/kg, 9.0 Bq/kg and 8.6 Bq/kg for Bandırma Fertilizer Factory (BFF), respectively. Radium equivalent activity (Raeq) and activity concentration index (I ? ), alpha index (I?), absorbed gamma dose rate in indoor due to the external exposure (DR) and corresponding effective dose rate (HR) were calculated to evaluate the exposure risk arising due to the use of these raw materials. For the BFF phosphogypsum samples, the mean value of Raeq is above the limit of 370 Bq/kg recommended for the safe use of construction materials, while for the MFF phosphogypsum samples, the mean value of Raeq is lower than the limit.