Radiation Exposure to Natural Radioactivity in Crude Oil and Petroleum Waste from Oil Fields in Ghana; Modelling, Risk Assessment and Regulatory Control.

Abstract

In this research work radiological hazards and risks to members of the public and workers from exposure to natural radioactivity as a result of crude oil production activities and waste generation from the Saltpond and Jubilee oilfields of Ghana, have been investigated via several exposure pathways using alpha spectrometry after radiochemical separation, nondestructive gamma spectrometry, Scanning Electron Microscope (SEM) and Inductively Coupled Plasma Quadrupole-Based Mass Spectrometry (ICP-QMS) and other complimentary analytical tools. Additionally, in this study a Human health risk assessment model for cancer risk associated with NORM (Naturally Occurring Radioactive Material) components in produced water was developed. Characterization and determination of specific activities of 234U, 238U, 210Po, 230Th, 232Th, 226Ra, 210Pb, 234Th, 228Ra, 228Th, 224Ra, and 40K for several environmental and NORM waste samples in different matrices have been established. The elements Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Na, P, Pb S, Si, Sr, and Zn were identified and semi qualitatively quantified by Scanning Electron Microscope for NORM waste samples. The total annual effective dose of 0.35 mSv.y-1 obtained for all exposure pathways for the public in this study was below the International Commission on Radiological Protection (ICRP) recommended dose limit of 1 mSv.y-1 for members of the public, whilst the total annual effective dose of 80.86 mSv.y-1 obtained in this study for workers clearly exceeded the ICRP recommended dose limit for an occupationally exposed worker of 20 mSv.y-1, averaged over 5years, but not exceeding 50 mSv.y-1 in any single year. The estimated total lifetime fatality cancer risk and the lifetime hereditary effect values were 1.3 x 10-3 and 4.9 x 10-5 for the public, and 23.2 x 10-2 and 5.7 x 10-3 for adult workers respectively. In conclusion, radium concentrations obtained in this study for scale, sludge and produced water from the oilfields of Ghana are of radiological importance and hence, there may be the need to put in place some measures for future contamination concerns due to their bioavailability in the media and bioaccumulation characteristics. The results from this study will assist in decision-making for future set-up of appropriate national guidelines for the management of NORM waste from the emerging oil and gas industry in Ghana.