Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

A gamma spectrometric analysis of rock samples collected from the Precambrian Oban Massif, southeastern Nigeria, was performed to determine some primordial radioelements’ activity concentrations: U-238, Th-232, and K-40, their associated radiological hazards. The mean radionuclides determined be 1073.06 ± 0.65, 160.74 1.32, 250.76 0.91 Bq·kg−1 for 40K, 238U, 232Th, respectively, showing that they are inhomogeneously distributed, with changing type location. concentrations highest in biotite garnet schist, quartz diorite, gneiss domains. values hazards 0.08 (alpha index), 2.15 Bq·kg−1(gamma 2.06 Bq·kg−1(internal) 1.63 (external4.30 Bq·kg−1(representative level index6), 602.23 Bq·kg−1, (radium equivalent), 780 nGy·h−1 (total absorbed dose rate), 270.91 (indoor), 509.78 (outdoor), 624.99, 1329.07 1954.06 mSv·yr−1 (outdoor, indoor total annual effective equivalent, respectively), 6448.40 (cumulative excess lifetime cancer risk) 248.94–3761.47 (annual gonadal equivalent). These results higher than various permissible limits (except at Ako Community) suggest rocks area may unsuitable constructing dwelling places. It is strongly advised basic safety standards precautionary measures recommended by European Commission should strictly adhered while dealing these rocks.