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 localand foreign locations were collected from different factories in Riyadh Region. Thesamples were crushed, dried in controlled furnace for around twenty four hours, andthen stored for four weeks in ½ l plastic Marinelli beakers. The gamma radiation of thesamples was measured, employing high resolution ã- ray spectroscopy with anaccumulating time for about 80000 sec. each. From the measured ã-ray spectra, activityconcentrations 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 forgranite 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 indicesand absorbed dose rate for all samples were estimated.