Natural radionuclides in rock and radiation exposure index from uranium mine sites in parts of Northern Nigeria

Abstract

Radiation exposure in humans can emanate from natural radionuclides through uranium and thorium decay series as well as40K due to emitted ionising radiations. It is important to estimate the exposure of humans to the diverse sources of radiation. In this study, the activity concentrations of natural radionuclides238U and232Th in granitic rock samples from uranium mine sites in parts of Northern Nigeria were measured, by inductively coupled plasma-mass spectrometry. The highest values of238U and232Th concentrations (924.56 ± 17.13 and 21.96 ± 1.28 Bq/kg, respectively) were observed at Mika-I and Riruwai. Furthermore, the radiological exposure parameters (i.e., absorbed dose rate in air [D], annual effective dose [external], radium equivalent activity (Raeq), external exposure index (Hex), internal exposure index (Hin), and representative level index (Iγand Iα) were estimated and compared to the international recommended values. In terms of terrestrial gamma radiation from granitic rock within the study area, it does not pose any significant radiation exposure to the workers and dwellers.

Keywords

• absorbed dose
• inductively coupled plasma-mass spectrometry
• radioactivity
• radiological exposure
• uranium ore