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

The activity concentrations of Ra-226, Th-232 and K-40 have been measured by gamma spectroscopy (sodium iodide Nal(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 Ra-226, Th-212 and K-40 (Bqkg(-1)) in phosphate rocks were 665.8 +/- 3.4, 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 gamma-radiation dose received by the workers of the phosphate mine are 538 and 418 mu Sv/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. (c) 2005 Elsevier Ltd. All rights reserved.