226~Ra, 232~Th and 40~K concentrations in igneous rocks from eastern desert, Egypt and its radiological implications

摘要

By applying high-resolution γ-ray spectroscopic system, the various radionuclides of the granite samples have been identified quantitatively based on the characteristic spectral peaks. The radionuclides 226Ra, 232Th and 40K concentrations measured as well as radiological parameters, for 49 granite samples were calculated. This subject is important in environmental radiological protection, since granites are widely used as building and ornamental stones. The variation in concentration of radionuclides for the Um Taghir area can be classified into two regions of low and high natural radioactivity. In old granite, the measured γ-ray spectra, activity concentrations were determined for 226Ra (from 2.9±1 to ), 232Th (range from 1.4±1 to ) and 40K (from 132±11 to ), in younger granite 226Ra (from 8.9±3 to ), 232Th (range from 9.8±3 to ) and 40K (from 471±22 to ). In Wadi Karim area these values were (14.0±4–227.0±15, 10.5±3–183.0±14 and 2299±48–). The highest values of 226Ra, 232Th and 40K concentration (9087±95, 3834±62 and ,respectively) were observed in anomalies samples at Um Taghir region. Radium-equivalent activities (Raeq) in addition to the internal hazard index (Hin) have also been determined. In Um Taghir samples Raeq varies between 15 and (old granite), 144– (younger granite) which exceeds the permitted value and hazard index (Hin) (0.05–1.74), (0.65–62.34) which is higher than 1, the corresponding values in Wadi Karim samples were 206– and from 0.59 to 2.46, respectively. The total absorbed dose rates in air calculated from the concentrations of the three radionuclides ranged from 8 to , and the external annual effective dose rate of the areas were determined to be between 0.04 and . This study provides a baseline map of radioactivity background levels in the Egyptian environment and will be used as reference information to assess any changes in the radioactive background level due to geological processes.