POTENTIAL OCCUPATIONAL RADIATION EXPOSURE DUE TO NATURALLY OCCURING RADIOACTIVE MATERIALS (NORM) ARISING FROM EXPLOITATION OF RARE-METAL PEGMATITES OF THE IBADAN-OSHOGBO FIELDS, OLODE, IBADAN, SOUTHWESTERN NIGERIA

Rock, ground water and mine waste samples collected from the Gbayo mines near Olode village, Southeastern Ibadan, Nigeria, were investigated with the aim of determining the levels of radioactivity due to naturally occurring radioactive materials (NORM) associated with gemstone (beryl) mining in the area, and to assess the health implications of the exploitation.

Fifteen (15) samples comprising rocks, mine wastes and water were obtained from three (3) mines while a sample of topsoil collected two kilometers away from the mine site served as control. The activity concentrations due to ²¹⁴Bi in the ²³⁸U decay series and ²⁰⁸Tl in the ²³²Th decay series and ⁴⁰K were determined using the HPGe gamma ray spectrometer at the National Institute for Radiation Protection and Research (NIRPR), University of Ibadan, Ibadan.

The activity concentration of the radionuclides from these samples range between 86.42 ± 6.67 Bq/Kg and 2200.71 ± 92.04 Bq/Kg, 3.00 ± 2.05 Bq/kg and 13.11 ± 5.81 Bq/kg, 6.09 ± 1.12 Bq/kg and 11.95 ± 1.97 Bq/kg for ⁴⁰K, ²³⁸U and ²³²Th respectively. The absorbed dose rate for the samples range between 8.99 nGy/hr and 112.97 nGy/hr and their corresponding dose equivalent range between 0.005 mSv/yr and 0.692 mSv/yr. The gemstone bearing pegmatite rock from mine 1 has the highest dose equivalent value of 0.692 mSv/yr but this value is lower than the 1 mSv/yr threshold limit set by the International Commission on Radiation Protection (ICRP) for the general public.