Disequilibrium in naturally occurring radioactive series in some phosphate ores

► Eight phosphate ore samples were studied. ► An atomic absorption spectrometry was applied for the elements concentrations. ► Mineral and chemical composition were determined by X-ray diffraction spectrometry. ► Concentrations of 238U, 226Ra and 232Th series and 40K were measured by a gamma-ray spectrometry. ► Results show disequilibrium in the 238U series and 232Th series.