Determination of Health Risk Coefficients for Natural Radioactive Elements in Crude Oil Produced from Al Gharraf Oil Field

Abstract

Natural radioactive materials (NORM) that accompany oil and gas production pose a real problem for the environment and man, where can these radioactive substances that pose a significant threat to workers in extraction of crude oil if the concentrations of these substances exceeded the permissible limits. Natural radioactivity due to U-238, Th-232, Ra-226, Ra-228 and K-40 in crude oil samples collected from al Gharraf oil field in Thi Qar province, south of Iraq measured using gamma ray spectrometry system based on 3” x 3” NaI (Tl) scintillation detector. The radioactivity concentrations of U-238,Th-232,Ra-226,Ra-228 and K-40 values in the studied oil samples are ranged (0.92-5.0 Bq / kg) with average of 2.592 Bq / kg ,(3.423-4.30  Bq) / kg with average of 3.819 Bq / kg , (1.611-6.811 Bq / kg) with an average  of 3.802 Bq / kg, (1.15-4.62 Bq / kg) with an average of 2.947 Bq / kg and (60.45-138.88  Bq / kg) with average of 97.324 Bq / kg , respectively. The equivalent concentrations for each of Ra -226 and Th-232 and K-40 has been calculated for all samples was found between (7.60-24.04) Bq / kg with average of 15.92 Bq / kg , (5.39-16.98) Bq / kg with average of 10.74 Bq / kg and (98.78-313.10) Bq/Kg with average of 98.78 Bq / kg respectively.  The absorbed dose for these concentrations were calculated using three equations supported by ICRP, UNSCEAR and BECK and found that the absorbed dose according to ICRP,UNSCEAR and BECK for all samples ranged between (1.378-5.675) with average (3.416) , (11.00-3.85)  with average (6.991)  and (11.496-3.881)  with average (7.480) , respectively. The calculated values of the annual effective dose rate and excess lifetime cancer risks (ELCR) are in between  with average) and (0.591  -2.436591) with average (1.465 (, respectively. The external and internal hazard index also calculated and found are ranged between   and (0.023-0.08 (  ) with average (0.041) and (0.049), respectively. The measured activity concentrations of radionuclides were compared with the worldwide reported data. This study shows that the measured crude oil samples do not pose any significant source of radiation hazard and are safe for workers in these areas so that all the measured and calculated parameters is within the limits allowed by the recommendations of ICRP,WHO,UNSCEAR .