Evaluation of Naturally Occurring Radioactive Materials (NORMs) in Inorganic and Organic Oilfield Scales from the Middle East

摘要

The distribution of natural nuclide gamma-ray activities and their respective annual effective dose rates, produced by potassium-40 (40K), uranium-238 (238U), thorium-232 (232Th), and radium-226 (226Ra), were determined for 14 oilfield scale samples from the Middle East. Accumulated radioactive materials concentrate in tubing and surface equipment, and workers at equipment-cleaning facilities and naturally occurring radioactive materials (NORMs) disposal facilities are the population most at risk for exposure to NORM radiation. Gamma-spectra analysis indicated that photo-gamma lines represent the parents of 10 radioactive nuclides: 234Th, plutonium-239, actinium-228, 226Ra, lead-212 (212Pb), 214Pb, thallium-238 (208Tl), bismuth-212 (212Bi), 214Bi, and 40K. These nuclides represent the daughters of the natural radioactive series 238U and 232Th with 40K as well. The mean activity concentration of 238U, 232Th, and 40K were found to be 25.8 ± 11.6, 18.3 ± 8.1, and 4487.2 ± 2.5% Bq kg−1 (average values for 14 samples), respectively. The annual effective dose rates and the absorbed doses in air, both indoor and outdoor, for the samples were obtained as well. The results can be used to assess the respective hazard on workers in the field and represent a basis for revisiting current engineering practices.