The natural radioactivity in phosphate deposits from Sudan

The natural radionuclide content of phosphate deposits at Uro and Kurun in Eastern Nuba mountains in the state of Kordofan (Western Sudan) and soils was determined radiochemically and gamma spectrometrically. The analyses were performed for natural uranium and thorium, 210Po, 226Ra and 40K. The data indicate that 238U and its decay products contribute primarily to the high natural radioactivity of phosphate ores. At maximum, we found an activity concentration of 2600 Bq/kg natural 238U. From the values obtained, the dose rates over agricultural areas, resulting from the use of ground rock phosphate as fertilizers estimated under extremely conservative assumptions, result in an additional external radiation exposure for members of the population of 5.42 × 10−9 nGy/a and 1.13 × 10−9 nGy/a for Uro and Kurun rock phosphates, respectively. These results show that the natural radionuclides contained in Uro and Kurun ground rock phosphate contribute very little to the average terrestrial radiation exposure to the population.