Concentrations of 226Ra, 232Th and 40K in industrial kaolinized granite

Activity concentrations of 226Ra, 232Th and 40K in 120 kaolinized granite samples imported in Serbia from the Motajica mine, Bosnia and Herzegovina, were measured. The 226Ra concentration ranged from 61 to 319 Bq kg−1, the 232Th from 44 to 272 Bq kg−1, and the 40K from 590 to 1470 Bq kg−1. The frequency distribution of 40K concentrations was near-Gaussian, where those of 226Ra and 232Th were right-skewed. In 6 samples, the gamma index, I, was higher than 2, which exceeds the exemption dose criterion (0.3 mSv y−1). The absorbed dose rate and annual effective doses for workers in the ceramic industries in Serbia who worked with kaolinized granite were below levels of concern.