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.