Gamma radiation measurements of naturally occurring radioactive samples from commercial Egyptian granites

Due to the widespread use of granites as building and ornamental materials, measurements of natural radioactivity for a total 27 selected samples of commercial granites used in Egypt were carried out by using a high pure germanium detector. The activity concentrations of Ra-226, Th-232 and K-40 of commercial granites ranged from 25 to 356, 5 to 161, and 100 to 1,796 (Bq kg(-1)), respectively. The concentrations of these radionuclides are compared with the international recommended values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate, the effective dose rate, and the hazard index have been calculated. The radium equivalent activity Ra-eq varied from 41 to 669 (Bq kg(-1)) which exceeds the permitted value (370 Bq kg(-1)) and the internal hazard index H (in) varied from 0.2 to 2.8 which is higher than 1. The absorbed dose rate due to the natural radioactivity in the samples under investigation ranged from 19 to 310 (nGy h(-1)). The total effective dose rates per person indoors were determined to be 0.09 to 1.5 (mSv year(-1)).