MEASUREMENTS OF NATURAL RADIOACTIVITY IN SOME KINDS OF MARBLE AND GRANITE USED IN RIYADH REGION

Thirty seven samples of marble and twenty samples of granite from both local and foreign locations were collected from different factories in Riyadh Region. The samples were crushed, dried in controlled furnace for around twenty four hours, and then stored for four weeks in l plastic Marinelli beakers. The gamma radiation of the samples was measured, employing high resolution γ- ray spectroscopy with an accumulating time for about 80000 sec. each. From the measured γ-ray spectra, activity concentrations were determined for marble samples 238U (0.71- 44.1Bq/kg), 232Th (0.10-32.0 Bq/kg), 226Ra (0.36-32.4 Bq/kg) and 40K (0.68-897.1 Bq/kg) while for granite 238U (0.03-314.4 Bq/kg), 232Th (0.02-186.4 Bq/kg), 226Ra (0.03-147.0 Bq/kg) and 40K (0.28 – 1531.7 Bq/kg). The radium equivalent activity, radiation hazard indices and absorbed dose rate for all samples were estimated