Dose assessment for natural radioactivity resulting from tiling granite rocks

The gamma radiation in samples of a variety of natural tiling granite rocks from different quarries located in South Sinai, Egypt used in the building industry is measured, using high-resolution g-ray spectroscopy. The samples pulverized, sealed in plastic Marinelli beakers, are analyzed in the laboratory with an accumulating time between 18 and 24 h each. Activity concentrations are determined for 238 U (from 18 to 361 Bq/kg), 232 Th (range from 20 to 316 Bq/kg) and 40 K (from 499 to 3089 Bq/kg). The total absorbed dose rates in air ranged from 42 to 440 nGy/h. The external hazard index ranged (from 0.23 to 2.49), the internal hazard index ranged (from 0.28 to 3.38), and the activity utilization index ranged (from 0.69 to 5.90). Applying dose criteria recently recommended by the European Union for superficial materials, 25 of the samples meet the exemption dose limit of 0.3 mSv/year, two of them meet the upper dose limit of 1 mSv/year and only one clearly exceeds this limit.