Estimation of possible radiological hazards from natural radioactivity in commercially-utilized ornamental and countertops granite tiles

The aim of this study is to estimate natural radioactivity levels of commercially-utilized ornamental or countertops granite tiles collected from major retailers in Turkey and possible radiological hazards from usage of these materials by calculating external exposure and internal index, indoor absorbed gamma dose rate and the corresponding annual effective dose. The activity concentrations of Ra-226, Th-232 and K-40 were determined for 42 kinds of different granite tiles using high-resolution gamma-ray spectrometer. The activity concentration of Ra-226 Th-232 and K-40 varied from 9.2 to 192.5 Bq kg(-1) (with a mean of 88.4 +/- 6.9 Bq kg(-1)), 7.5 to 344.6 Bq kg(-1) (with a mean of 95.3 +/- 0.0 Bq kg(-1)) and 92.1 to 4155.9 Bq kg(-1) (with a mean of 1055.2 +/- 103.0 Bq kg(-1)), respectively. The estimated radiological hazard indices were revised in the light of the relevant national and international legislation and guidance. The values of the radiological hazard indices were found to be within relevant all limit values for superficial materials. The indoor absorbed gamma dose rates estimated from the activity concentrations of Ra-226, Th-232 and K-40 and the corresponding annual effective doses varied from 4.74 to 85.27 nGy h(-1) and 0.02 to 0.42 mSv, respectively. (C) 2012 Elsevier Ltd. All rights reserved.