Concentrations of Ra, Th and K in industrial kaolinized granite.

Activity concentrations of Ra, Th and K in 120 kaolinized granite samples imported in Serbia from the Motajica mine, Bosnia and Herzegovina, were measured. The Ra concentration ranged from 61 to 319 Bq kg, the Th from 44 to 272 Bq kg, and the K from 590 to 1470 Bq kg. The frequency distribution of K concentrations was near-Gaussian, where those of Ra and Th were right-skewed. In 6 samples, the gamma index, I, was higher than 2, which exceeds the exemption dose criterion (0.3 mSv y). 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.