Natural Radionuclides in the Building Materials From the Region of The Small Carpathians

Distribution of radionuclides in the main rock types: granodiorites, biotite-gneisses, black shale and amphibolites at the locality Pezinok - Kolársky vrch was studied in samples from two boreholes. Concentrations of 238U, 232Th and 40K in the samples were analysed by gamma spectroscopy (concentrations of 238U were 0.091 - 37.800 mg/kg, 232Th 0.534 - 13.234 mg/kg, 40K 0.116 - 5.162 mg/kg). The highest average 238U concentration was in black shale, highest average 232Th concentration in granodiorite and highest average 40K concentration in granodiorite. Activities of 238U were determined within the range of 1.092 - 48.960 Bq/kg (with exception of one anomalous value - 453.6 Bq/kg), activities of 232Th within the range of 2.189 - 54.298 Bq/kg and activities of 40K within the range of 30.933 - 1,376.499 Bq/kg. The source of 238U and 232Th (and partially also of 40K) is in the granodiorite intrusion. During the metamorphic process, Uranium was mobilised to the black shales. The concentrations and consequently the total activities of 238U, 232Th and 40K in the studied rock samples exceed the permitted limit values for building materials. It is possible to recommend their utilisation only for external purposes.