Specific activity and hazards of granite samples collected from the Eastern Desert of Egypt

Fifty granitic rock samples were collected from different plutons in the central part of the Eastern Desert of Egypt and were analyzed for specific concentrations of U-238, Th-232 and K-40 radionuclei. The measurements were carried out using a high performance and stability Nomad Plus spectroscopy system attached to a 1.7 keV (FWHM) HPGe detector. The spectra were analyzed using the direct gamma counting comparison method as well as the traditional absolute efficiency curve method. The highest average value of U-238 concentration (1184 Bq kg(-1)) was observed at El Misikat region whereas the highest average values of 40K and Th-232 concentration (2301.8 and 162.5 Bq kg(-1) respectively), were detected at Gabal Homret Waggat area. The radium equivalent activity (Raq), the absorbed dose rate (D), the external hazard index (H-ex) and the annual gonadal dose equivalent were also calculated and compared to the international recommended values. Radon exhalation rate from the rock samples were measured using the activated charcoal canister method. The average value of radon exhalation varies from 0.052 to 0.69 Bq m(-2) h(-1) and depends on the specific concentration of uranium. (C) 2004 Elsevier Ltd. All rights reserved.