Natural radioactivity and dose assessment for phosphate rocks from Wadi El-Mashash and El-Mahamid Mines, Egypt

The activity concentrations of 226Ra, 232Th and 40K have been measured by gamma spectroscopy (sodium iodide NaI(Tl) detector) in phosphate rock samples, collected from the Wadi El-Mashash, a site located in the central eastern desert, and El-Mahamid in the Nile valley, Egypt. The average activity concentrations of 226Ra, 232Th and 40K (Bq kg−1) in phosphate rocks were 665.8 ± 33.4, 329.4 ± 17 and 587.6 ± 29.4 for Wadi El-Mashash and 566.8 ± 28.6, 217.3 ± 11.8 and 560.1 ± 28 for El-Mahamid, respectively. The corresponding values for shale rocks were 85.2 ± 5.7, 93.3 ± 5.6 and 303.1 ± 15.2 Bq kg−1, respectively. As a measure of radiation hazard to the occupational workers and public, the Ra equivalent activities, representative level index and dose rates due to natural radionuclides at 1 m above the ground surface were estimated. The calculated external γ-radiation dose received by the workers of the phosphate mine are 538 and 418 μSv/y, which is far below the permitted dose of 20 mSv/y recommended by the International Commission of Radiation Protection [ICRP-60, 1990. Radiation Protection: 1990 Recommendation of the International Commission on Radiological Protection, Oxford, Pergamon Preis.] for workers.