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

Authors: Lazaro H. Meza; Mohsen A. Mandour; Mahmoud H. Shalaby; Mohamed H. Hassan; Nader A. Mohamed

Addresses: Department of Nuclear & Radiation Engineering, Alexandria University, Alexandria, Egypt ' Department of Nuclear & Radiation Engineering, Alexandria University, Alexandria, Egypt ' Nuclear Material Authority, Cairo, Egypt ' Department of Nuclear & Radiation Engineering, Alexandria University, Alexandria, Egypt ' Egyptian Second Training Research Reactor, Cairo, Egypt

Abstract: 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.

Keywords: natural radioactivity; activity concentrations; absorbed dose rate; outdoor annual effective dose; radium equivalent activity; external hazard indices; uranium concentration; phosphate mines; case study; Tanzania; terrestrial radionuclides; low radiation.

DOI: 10.1504/IJLR.2015.071766

International Journal of Low Radiation, 2015 Vol.10 No.1, pp.74 - 92

Received: 06 Jun 2015
Accepted: 12 Jul 2015
Published online: 17 Sep 2015 *