Evaluation of the terrestrial radionuclides and the occupational effective doses at a phosphate mills

Phosphate rocks are the raw materials for fertilizer production. This study aims to evaluate the occupational radiological hazards associated with phosphate rock processing. The average activity concentrations were 825 ± 41, 166 ± 8.3, 12 ± 0.6, and 1333 ± 67 (Bq/kg) for U-238, Ra-226, Th-232, and K-40 respectively. All these concentrations are typical for phosphate rocks. The average absorbed dose rate is 139 ± 7 (nGy/h), which is higher than the worldwide average, reflecting the relative high concentrations of U-238, Ra-226, and K-40. The average total annual effective dose is 0.53 ± 0.03 (mSv/y). All the radiological parameters are lower than the recommended limits.