Evaluation of radiological impacts of tenorm in the Tunisian petroleum industry.

The health impacts associated with uncontrolled release of TENORM in products and wastes released in the petroleum industry are of great concern. In this study, evaluation of TENORM in the Tunisian petroleum products and wastes is presented. Fourteen products samples, twelve waste samples and three samples from the surrounding environment were collected from the Tunisian Refinery STIR site and from two onshore production oilfields. The activity concentrations of (232)Th, (226)Ra and (40)K for all samples were determined using gamma-ray spectrometry with High Purity Germanium (HPGe) detector. The activity concentrations of (224)Ra were calculated only for scale samples. The radium equivalent activity, external and internal hazard indices, absorbed doses rates in air and annual effective dose were also estimated. It was noticed that maximum value of Ra(eq) activity was found to be 398 Bq/kg in scale (w8) collected from an onshore production oilfield which exceeds the maximum Ra(eq) value of 370 Bq/kg recommended for safe use. All hazard indices indicated that scale samples (w6, w7, w8 and w11) could be a significant waste problem especially sample (w8). In this study, the radium isotopic data were used to provide an estimate of scale samples ages by the use of the (224)Ra/(228)Ra activity ratio dating method. Ages of collected scales were found to be in the range 0.91-2.4 years. In this work, radioactivity (NORM contamination) in samples collected from the refinery STIR are showed to be insignificant if compared to those from onshore oilfield production sites.