ASSESSMENT OF RADIATION EXPOSURE LEVEL FROM SOME SCRAP METAL DUMP SITES IN NASARAWA STATE, NIGERIA.

Scrap yards, steel works and nonferrous metal smelters and refiners are increasingly detecting radioactive substances in incoming scrap metal as the result of losses, accidents or inadvertent disposal of radioactive material. In this study, the radiation exposure rate emanating from scrap metals dump site was assessed and the radionuclides responsible for the emission identified using an Interceptor – Spectroscopic personal radiation detector (SPRD). Sixteen (16) scrap metal dumpsites were selected at random across four Local Government Areas (Nasarawa, Lafia, Akwanga, and Keffi) of Nasarawa State, Nigeria and the gamma activity level in μrem/hr on three (3) randomly selected points on each of the scrap metal dumpsite was determined. A reading was taken on point 100m away from each of the scrap metal dump site. Results shows that, the highest annual effective dose equivalent was observed in Akwanga (AKW4) scrap metal dumpsite with annual effective dose equivalent of 0.2167mSv/yr, followed by Keffi (KEF1) with annual effective dose equivalent of 0.1758mSv/yr. The scrap metal dumpsite with the lowest annual effective dose equivalent were observed in Lafia(LAF3) and (LAF4) with annual effective dose equivalent of 0.0613mSv/yr. The excess lifetime cancer risk of 0.7585 × 10-3 was the highest value recorded in AKW4, while the lowest value was found to be 0.2146 × 10-3 in LAF3 and LAF4. The radionuclides identified are Med Pd-103, Ind Nb-95, Med Lu-176, Ind Xe-135, Ind Te-132,Ind La-140, Nat U-233, Med Se-75, Ind Cr-51, Ind Lu-176, Nat Th-177, Med Tc-99m, Ind La-140 and Med I-125 with thrust level ranging from 42- 83%. These values were below the ICRP dose limit of 1mSv/yr indicating that, the environment around these scrap metal dumpsites is safe. The excess lifetime cancer risk value (ELCR) obtained in some locations are higher than the world average value of 0.29 × 10-3. Therefore, we recommend that scavengers, workers and the public around the scrap dumpsites are to minimise the period of their stay within the dumpsites, so as to minimise the risk of developing cancer in future.