Natural Radioactivity in Granites Used as Countertops in the New Buildings of King Abdulaziz University

Forty two samples of different granite slabs that used extensively as countertops in the new buildings of King Abdulaziz University were collected randomly and analyzed by γ-spectrometry for natural radioactivity in a purpose of radiation protection. For comparison, twenty two samples of other building materials were collected and analyzed. Among the analyzed samples the granite stones had activity concentration, ranging from 27 to 190, 21 to 352 and 529 to 1352 Bq/kg for 238U, 232Th and 40K, respectively. Among the granite samples, the highest activity concentration was found in the brown granite of the old buildings. The lowest activity concentrations were found in mica and the concrete mix, ranging from 10 to 18, 6 to 15 and 225 to 419 Bq/kg for 238U, 232Th and 40K, respectively. The average activity concentrations of both 238U and 232Th in the analyzed building materials follow the sequence in descending order: granites pottery mica ≈ concrete mix. The radiation hazard indices were calculated and compared to the international accepted limits. Except values of the brown granite of the old buildings, all other values were compiled with the international limits. The obtained results have been discussed in detail.