Assessment of occupational external radiation exposure of workers in the Southwest of Libya using portable NaI detector

Abstract

In this study, gamma dose rates generated from the naturally occurring radioactive materials (NORM) were measured in the waste streams of a large scale and sludge onshore petroleum operations. Measurements conducted in this work involved: sludge recovery from separation tanks, sludge forming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was carried out in many places of different terrain of an operation oil exploration and production in Murzuq basin in the Southwest of Libya. The radiation dose rates were measured using portable InSpector-1000. A total of 400 dose rates were acquired. The highest dose rate was 70 μSv/h acquired in sludge stored in barrels. The estimated mean annual equivalent doses in this field were in the range of 0.2–2.8 mSv/y in the first scenario, while in the second scenario the calculated mean annual equivalent doses were in the range of 0.04–0.68 mSv/y. It is assumed that workers may face various exposures in the field where measurements took place, considering the total annual effective dose to be 1.53 mSv/y. The main radioisotopes detected in these samples indicated by the display of the measuring device were 226Ra and 228Ra but detecting both radioisotopes in the same run is not achievable by using the display of the screen.