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.

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The activity concentrations of some radionuclides ( 238 U, 234 U, 230 Th, 226 Ra, 232 Th, 40 K and 235 U) were measured by γ-ray spectrometry in order to study their behavior and the relation between them in Carboniferous rock samples collected from Gabal (mountain) Um-Hamd, southwestern Sinai, Egypt. The whole samples are located in the two limbs and trough of a synclinal form structure to identify the radionuclides migration processes which have occurred in these rock samples. The average activity concentrations of 238 U

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Specific activities (Bq/kg and ppm) of naturally occurring radionuclides were measured for about 57 samples from some household kits. The maximum specific activity values were 76.12, 118.37 and 3340.6 Bq/kg for U-238, Th-232 and K-40, respectively. The external exposure rate (µR/h) and dose rate (nG/h) were calculated. The maximum mean annual effective dose due to U-238 from Chinese ceramic dishes was 59.24 µSv/y, while the maximum mean annual effective doses due to Th-232 and K-40 were 126.31 and 63.81 µSv/y, respectively. The maximum total mean annual effective dose was 248.19 µSv/y for Portuguese dishes. The surface area concentration (Bq/m2) was calculated to estimate the annual equivalent dose to all organs and the effective dose due to contaminated ground. To estimate the annual effective dose, a value of 0.7 Sv/Gy was used for the conversion coefficient from the absorbed dose in air to the effective dose received by workers. The mean annual effective dose to workers due to U-238, Th-232 and K-40 is given using two methods: the first one is according to the International Atomic Energy Agency (IAEA) (2003) recommendations and the second one is a Monte Carlo technique for the dose calculations, which ranged from 0.0036 to 0.248 mSv/y for the first method and 0.0039 to 0.214 mSv/y for the second method. The total annual dose from U, Th and K for each organ shows that the lowest dose was received by the oesophagus, while the skin received the highest dose.