Radiochemical signature of radium-isotopes and some radiological hazard parameters in TENORM waste associated with petroleum production: A review study.

Large amounts of TENORM waste (produced water, scale, and sludge) are created in oilfields around the world, presenting radiological risks to employees, the public, and the environment since activity concentrations of radioactive substances were above the exemption levels accredited by several authorities. Using the activity concentration of the radium-isotopes (226Ra and 228Ra) in the waste, we determined the 'fingerprint' as a radiochemical signature and some relevant 'radiological hazard parameters' in this review. The majority of the reported residues take the form of radio-contaminated (produced water, scale, and sludge) generated in Egypt's oilfields or elsewhere include radium isotope activity concentrations (226,228Ra) that exceed the international exemption limit. The activity concentrations of 226Ra(238U-series) in produced water, scale, and sludge waste were 0.04-1,480 Bq/L, 1.1-2,015,000 Bq/kg, and 1-120,800 Bq/kg, respectively, whereas 228Ra (232Th-series) was 0.34-250 Bq/L, 1.8-1,428,000 Bq/kg, and 10-122,830 Bq/kg, respectively. The radioactivities of radium isotopes were found to be above the exemption values recognized by WHO, IAEA, IOGP, EC, and ICRP in 95, 82, and 58% of produced water, scale, and sludge waste, respectively. The 226Ra(238U)/228Ra(232Th) ratio, from the other hand, was estimated to be utilised as a 'radiochemical fingerprint', or signature in the reported TENORM residues. The radium isotopes ratio in produced water, scale, and sludge waste in Egypt's oilfields is 0.41-4.45 (av. 1.98 ± 1.37, coefficient of variation, COV %: ∼69%), 0.2-21.4 (av. 4.3 ± 4.7, ∼109%), and 1.4-52.2 (av. 9.6 ± 15.3, ∼159%), respectively. For produced water, scale, and sludge waste, the 226Ra/228Ra ratios are 0.12-9.1 (av. 1.43 ± 1.72, ∼120%), 0.2-159 (av. 7.78 ± 23.5, ∼302%), and 0.8-223.5 (av. 14.1 ± 45.4, ∼322%) in global oilfields. The radiological hazard parameters (Ig, Ia, E◦, EG, and ELCR) owing to radium isotopes or 222Rn in most scale and sludge residues, as well as a small percentage of produced water, are all over the allowed safe limits. Substantial differences in the radium isotopes ratio in the reported waste can be attributed to thier geological, chemical, physical, and/or operational constraints. However, from the different perspectives of remediation and/or radiation protection programs, these values can be employed as a guidance for organizations investing in oil and gas production.

Examination of the parameters affecting of 222Rn emanation for some industrial and environmental samples using gamma-spectroscopy.

The present work aims to radiologically characterize five samples (monazite, zircon, scale waste originating from petroleum production, black sands and phosphate rocks) from different industrial applications and environments in the Egyptian territory. The first section of the present work discusses the measurement and analysis of 226Ra, 232Th and 40K concentrations. Moreover, the assessment of the hazard indices is given in terms of radium equivalent (Raeq), external hazard index (Hex), internal hazard index (Hin), gamma-activity index (Iγ) and alpha-activity index (Iα). The second section deliberates the 222Rn gas emanated from the samples and studies the physical parameters affecting the emanation process. The results found that the monazite sample has the highest concentration of 226Ra, 232Th and 40K; however, it reached 54435, 442105 and 583 Bq.kg-1, respectively, between the studied samples. Furthermore, black sands and phosphate rock samples exhibit the lowest concentration of 226Ra, 232Th and 40K. Results also show that the radon emanation coefficients decrease while the density of materials increases.

Performance characteristics and validation of alpha particle spectrometers for radiometric analysis of natural and anthropogenic radionuclides of environmental impacts.

Alpha spectrometry is one of the greatest nuclear techniques for identification and quantification of α-emitters in the environment due to nuclear fuel cycle operations, nuclear materials and geochemical studies or forensic medicine investigations. This study was conducted to re-evaluate and optimize the factors affecting the performance of a multi-chamber alpha spectrometer (EG&G Ortec) used in our laboratory using an aged α-source of 232U in equilibrium with its decay products. The results shown that the energy calibration within energy window 4-9 MeV has been done using alpha particle emissions of 232U (t1/2.70.6 y) and its decay products with good linear fitting (R2 > 0.999). At a source to detector spacing of 10 mm, the efficiency of the detectors varied between 15 and 20%; while the better resolution (FWHM) was ~36 keV. These values are lower than those warranted when supplied before 20 years. The minimum detectable activity (MDA) of the detectors varies between 0.8 and 3.1 mBq for the chamber in use. The alpha spectrometer was also verified by certified reference samples to measure activity concentration of alpha emitters (e.g., 238U, 232Th, 226Ra and 241Am) with acceptable coefficient of variance (<10%), ζ-score (<3) and P-test (<25%). As a result, the optimized alpha spectrometer is valid and can be utilized for monitoring and assessment of natural and artificial α-emitters in different environmental compartments.

Kinetics and mechanism of radium-isotopes dissolution in TENORM scale waste associated with petroleum production using certain organic carbon source: lactic acid solution-case study.

The present study is conducted to explore the dissolution as inferred from the kinetic mechanism for radium-isotopes (228Ra, 226Ra, and 224Ra) in the TENORM scale waste deposited in oilfield pipes and equipment, Gulf of Suez, Egypt. The main efficiency factors for Ra2+-compound dissolution by lactic acid (LA) solution, e.g., reactive organic carbon (i.e., electron-donor source), have been investigated, and optimum chemical conditions have been determined. The obtained data were also employed to predict the leaching kinetics and mechanism of the Ra2+-isotopes removal by three shrinking core models (SCM, liquid film process-chemical controlled process-diffusion controlled process) and Arrhenius model. The maximum leaching percentage of Ra2+-isotopes reached to 55-60% at the optimal leaching conditions (0.3 M LA, 5 h, 25 °C, ϕ < 1 mm, S/L ratio 10/50 g mL-1). The Ra-isotopes removal proceeds kinetically by diffusion-controlled process. Activation energy (Ea) of the leaching process was 10.51 kJ mol-1. This value conforms that the leaching process for removal of Ra2+-isotopes in the TENORM scale waste by LA solution is controlled by a diffusion process. Values of thermodynamic parameters (∆Go, ∆Ho, ∆So) were determined and indicate that dissolution of Ra2+-isotopes in the studied waste is non-spontaneous and temperature dependent. Moreover, the leaching mechanism may be attributed to the dissolution of soluble exchangeable and acidic species of Ra2+-species and/or these due conversions of insoluble Ra-sulfate to more soluble Ra-sulfide and/or Ra-hydrogen sulfide by LA solutions.