Abstract
The radioactivity concentrations of 226Ra, 232Th and 40K in thirty samples representing the technically Naturally Occurring Radioactive Materials (NORM) in the Egyptian natural gas were investigated. The investigations were performed using a gamma ray spectroscopy technique. The obtained data were used to establish a data base for NORM concentrations during the different processing stages of natural gas and to estimate the associated radiation health hazard impacts. Great concern has been devoted to determine the specific activity of 210Pb as it represents all daughters originating from 222Rn that have relatively short half-lives. The samples were collected from the gas pipeline grid covering different areas in Egypt. Fifteen samples were taken from the gas pipelines, whereas the remaining samples were taken from the upstream facilities before pumping into the grid. The average activity concentrations of 226Ra, 232Th and 40k were found to be 16.2 ± 1.5, 10.50 ± 0.9 and 98.46 ± 6.03 Bq/kg for filter samples respectively. The corresponding average values for scale samples were 37.28 ± 3.1, 45.7 ± 2.6 and 621.79 ± 9.2 Bq/kg. The sludge samples gave average values of 14.97 ± 1.94, 9.99 ± 1.48 and 112.82 ± 5.82 respectively. These values are below the recommended international limits. In contrary, the average values of activity concentrations of waste water were found to be 4.895 ± 0.51, 2.241 ± 0.3 and 31.852 ± 2.31 Bq/kg respectively. The obtained results indicate that 226Ra content is higher than the recommended values for domestic or drinking water. Additionally, high values of the specific activity of 210Pb were found in both deposits and filter samples.
Highlights
Earth’s crust contains Naturally Occurring Radioactive Materials (NORM) at measurable concentrations
It is shown that the values of the specific activities of 210Pb for different samples are high in particular in the gas filter samples lying in the range from 250 to 1664 Bq/kg with an average value 260 ± 0.21 Bq/kg
The present results of NORM concentrations for samples collected from the Egyptian national gas grid and upstream processing plant and the associated calculated parameters can be used to drive the following conclusions: Sludge samples taken from the upstream plant showed the highest radioactity concentration with an average value of 37.28, 45.7and 621.79 for 226Ra, 232Th and 40K respectively
Summary
Earth’s crust contains Naturally Occurring Radioactive Materials (NORM) at measurable concentrations. The sources of most NORM are 226Ra, 232Th and 40K These isotopes are naturally present in subsurface formations from which oil and natural gas are produced. Radium-226 and radium-228 are the main radionuclides of concern in NORM wastes which are produced from the decay series of 238U and 232Th. Radium-226 and radium-228 are the main radionuclides of concern in NORM wastes which are produced from the decay series of 238U and 232Th Other radionuclides are those produced from the decay of 228Ra and 226Ra. radioactive isotopes such as uranium-238, radium-228and radon-222 are dissolved in very low concentrations during normal reactions between water and earth constituents such as rock. The isotope of radium which is slightly soluble can be mobilized in the liquid phases of formation and transported to the surface in the produced water stream.
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