A thorough investigation of the uranium concentration in phosphate mines: a case study of Minjingu phosphate mine, Arusha, United Republic of Tanzania

Using high resolution gamma ray spectrometry, the terrestrial radionuclides from all phosphate rock samples were measured and results are presented. From the measured gamma ray spectra, activity concentrations were determined for 226Ra/238U (range from 122.5±6.9 to 8060±806 Bq kg−1), 232Th (range from 13.2±0.8 to 1201.3±77.3 Bq kg−1), 40K (range from 12.9±1.3 to 1827.6±93.9 Bq kg−1) and 137Cs (range from 0.5±0.017 to 70.58±1.25 Bq kg−1) with mean of 1832.32±00, 447.62±00, 399.46±00 and 22.98±0.43 Bq kg−1 respectively. Radium equivalent activity ranges from 219.27±00 to 9127.07±00 Bq kg−1 with mean of 2433.56±00 Bq kg−1. The total absorbed dose estimated at 1 metre above the ground varies from 102.1 to 3967.8 nGyh−1 with an average of 1055.9 nGy h−1. Investigation of uranium recorded a peak of 650±65ppm, this suggests the existing U concentration is over three times greater than economically viable and production of a cleaner fertiliser is favourable.