RADIOACTIVITY AND RADIOLOGICAL IMPACT ASSESSMENT IN OTA-DUMPING SITE, OGUN STATE, NIGERIA

Background radiation levels and distributed radionuclides in Ota-dumping site were conducted in different stations to determine the concentrations of natural radionuclides and their possible radiological effects. The external gamma absorbed dose rate and concentration of radionuclides in the area were measured using portable hand-held plastic scintillometer (RS-125 Radiation detector). The activity concentrations vary from 2.47 ± 0.3 to 25.01 ± 1.0 BqK-1, 12.49 ± 0.8 to 105.97 ± 0.6 BqK-1 and 15.65 ± 0.2 to 46.95 ± 0.2 BqK-1 for 238U, 232Th and 40K respectively. The highest activity value of 238U, 232Th and 40K reported in stations 11, 12 and 7 respectively. The absorbed gamma dose rates exposed to people in the area varies from 12.65 ± 2.2 to 44.45 ± 6.6 nGry-1 with the highest value of 44.45 ± 6.6 nGry-1 noted 50 m away from the site at station 12. This could be attributed to the effect of geological features and dose rates from the dumping site tilted towards the Northeast Southwest. The annual effective dose, radium equivalent activity and external hazard index exposed to people in the area are 0.055 mSvy-1, 52.22 ± 0.6 BqK-1 and 0.4 respectively. All the values of radiological risks are within the recommended level by [18], but suggest that the inhabitants residing south western (SW) part of area should adjust if possible 500 m away from the dump-site to avoid long term accumulation which could pose cancer risk