Removal of 226Ra and 228Ra from TENORM sludge waste using surfactants solutions

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 (I_g, I_a, E_◦, E_G, 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.

Calculation of NaI(Tl) detector efficiency using 226Ra, 232Th, and 40K radioisotopes: Three-phase Monte Carlo simulation study

Thallium-activated sodium iodide (NaI(Tl)) detectors can be used in gamma cameras, environmental radiation assessments, including radiation emission levels from nuclear reactors, and radiation analysis equipment. This three-phase investigation aimed to model a standard NaI(Tl) detector using the Monte Carlo N-Particle eXtended (MCNPX) general-purpose Monte Carlo simulation techniques. Accordingly, a standard NaI(Tl) detector was designed along with the required properties. Next a validation study of the modelled NaI(Tl) detector has been performed based on the experimental results for absolute detector efficiency values obtained from 226Ra, 232Th, and 40K radioisotopes. Our findings indicate that the obtained absolute detector efficiency values are quite close to used experimental values. Finally, we used the modelled detector for determination of mass attenuation coefficients of Ordinary concrete, Lead, Hematite-serpentine concrete, and Steel-scrap concrete at 186.1, 295.22, 351.93, 609.31, 1120.29, 1764.49, 238.63, 911.2, 2614, and 1460.83 keV gamma-ray energies. Additionally, according to our findings, mass attenuation coefficients obtained from the newly designed detector are compatible with the standard NIST (XCOM) data. To conclude, continuous optimisation procedures are strongly suggested for sophisticated Monte Carlo simulations in order to maintain a high degree of simulation reliability. As a result, it can be concluded that the validation of the simulation model is necessary using measured data. Finally, it can also be concluded that the validated detector models are effective instruments for obtaining basic gamma-ray shielding parameters such as mass attenuation coefficients.

Selective adsorption of sodium dodecylbenzenesulfonate from a Cs ion mixture by electrospun mesoporous silica nanofibers

Sodium dodecylbenzenesulfonate (SDBS) is commonly used to remove radioactive nuclides such as Cs ions during decontamination of shut-down nuclear power plants. Potential environmental problems still remain because of the incomplete removal of large amounts of SDBS from radioactive liquid waste. For the first time, mesoporous silica nanofibers (MSFs) were fabricated for an efficient SDBS separation. MSFs were prepared by electrospinning using tetraethyl orthosilicate, a surfactant, and a template polymer; the product had a large surface area, a high pore volume, and a uniform pore size distribution. The internal pores or external surface were modified with quaternary ammonium salt, providing affinity to water and an electrostatic interaction with SDBS. The MSF-based adsorbent had excellent adsorption ability for SDBS (158.98 mg/g) over conventional adsorbents. In addition, the MSF-based adsorbent could selectively adsorb SDBS from a mixed solution of SDBS and Cs ions. Judging from the Freundlich pseuso second-order kinetic adsorption, the adsorption isotherm indicated that the SDBS adsorption was a kind of multilayer physisorption.

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 (E_a) 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 (∆G^o, ∆H^o, ∆S^o) 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.

Self-attenuation corrections for radium measurements of oil and gas solids by gamma spectroscopy

Beneficial reuse and resource recovery of produced water often require treatment to remove radium before valuable products are extracted. The radium content of the treatment waste solids and beneficial products must be accurately determined when evaluating the efficacy and social validity of such treatments. While gamma spectroscopy remains the recommended method for radium measurements, these measurements can be impacted by the composition/mineralogy of the solids, which influence the attenuation of the gamma decay energy - with denser sediments incurring greater degrees of attenuation. This self-attenuation must be accounted for when accurately measuring radium, otherwise radium measurements are found to be inaccurate, sometimes by as much as 50%. To meet industry needs, measurements should be both accurate and rapid, even for small sample sizes. Consequently, we propose a rapid method for accurate radium measurements with an empirical technique to account for sample attenuation in well-detector gamma spectroscopy. This technique utilizes the sample density and sample volume in the measuring vial. These corrections are relevant to a wide range of solid samples and sediment densities that may be encountered during treatment and management of oil and gas solids, including clays, environmental sediment samples, sand grains, and precipitated salts. These corrections can also be applied for situations were low volumes of material are present, as in bench scale studies, thereby rendering this technique applicable to a wider range of scenarios.

Characterization and radiological impacts assessment of scale TENORM waste produced from oil and natural gas production in Egypt

This study aims to identify the analytical and radiological characterization of scale TENORM waste produced from oil and natural gas productions in the western desert in Egypt and evaluates their radiological impacts. The mean activity concentration of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Ra, ²²⁴Ra, and ⁴⁰K measured in scale TENORM samples is 660 ± 63, 1979 ± 435, 1399 ± 211, 645 ± 104, 794 ± 116, and 556 ± 86 Bq/kg, respectively. Radiological hazard parameters (Ra_eq, Hex, Hin, etc.) were estimated form the scale TENORM waste sample. All the calculated hazard parameters were found greater than the permissible and recommended safe levels. So the exposure to radiations released from the accumulation of the petroleum scale TENORM waste may cause health risks to the operators and who inhale radioactive radon gases and/or ingest contaminants by radiotoxic nuclides of U, Th, Ra, and Pb. Also, the risks may be extended to the near and/or the general environment.

Raw material recovery from hydraulic fracturing residual solid waste with implications for sustainability and radioactive waste disposal

Unconventional oil and gas residual solid wastes are generally disposed in municipal waste landfills (RCRA Subtitle D), but they contain valuable raw materials such as proppant sands. A novel process for recovering raw materials from hydraulic fracturing residual waste is presented. Specifically, a novel hydroacoustic cavitation system, combined with physical separation devices, can create a distinct stream of highly concentrated sand, and another distinct stream of clay from the residual solid waste by the dispersive energy of cavitation conjoined with ultrasonics, ozone and hydrogen peroxide. This combination cleaned the sand grains, by removing previously aggregated clays and residues from the sand surfaces. When these unit operations were followed by a hydrocyclone and spiral, the solids could be separated by particle size, yielding primarily cleaned sand in one flow stream; clays and fine particles in another; and silts in yet a third stream. Consequently, the separation of particle sizes also affected radium distribution - the sand grains had low radium activities, as lows as 0.207 Bq g-1 (5.6 pCi g-1). In contrast, the clays had elevated radium activities, as high as 1.85-3.7 Bq g-1 (50-100 pCi g-1) - and much of this radium was affiliated with organics and salts that could be separated from the clays. We propose that the reclaimed sand could be reused as hydraulic fracturing proppant. The separation of sand from silt and clay could reduce the volume and radium masses of wastes that are disposed in landfills. This could represent a significant savings to facilities handling oil and gas waste, as much as $100 000-300 000 per year. Disposing the radium-enriched salts and organics downhole will mitigate radium release to the surface. Additionally, the reclaimed sand could have market value, and this could represent as much as a third of the cost savings. Tests that employed the toxicity characteristic leaching protocol (TCLP) on these separated solids streams determined that this novel treatment diminished the risk of radium mobility for the reclaimed sand, clays or disposed material, rendering them better suited for landfilling.

Concentrations of TENORMs in the petroleum industry and their environmental and health effects

Crude oil and its products and wastes are among the significant sources of naturally occurring radioactive materials (NORMs). These materials may be enhanced to high levels due to technological and human activities, which are called technologically enhanced naturally occurring radioactive materials (TENORMs). Thus, the average radioactivity of these radionuclides sometimes exceeds the exemption level of 10 000 Bq kg⁻¹, which is recommended by the IAEA's safety standards. TENORMs in the oil and gas industry may generate greater radioactivity levels, which eventually represents potential environmental and health risks. This will require continuous attention by monitoring and surveillance during routine processes in the petroleum industry. In this paper, a comprehensive review of the published literature is conducted to evaluate the TENORM concentrations in the oil and gas industry. Moreover, their environmental and health hazards in different regions of the world are discussed.

Crude oil and its products and wastes are among the significant sources of naturally occurring radioactive materials (NORMs).

Determination of 226Ra at low levels in environmental, urine, and human bone samples and 223Ra in bone biopsy using alpha-spectrometry and metrological traceability to 229Th/225Ra or 226Ra

²²⁶Ra is a natural radioelement emitting α and γ radiations. It can be highly concentrated in TENORM materials from the petroleum or fertilizer industries. In Switzerland, ²²⁶Ra is currently a radioactive inheritance problem from the watch industry. Furthermore, ²²³Ra is a radium isotope used in nuclear medicine to treat bone metastasis. There exist several methods to measure radium using alpha or gamma spectrometry or using ²²²Rn emanation technique. The limitations of these methods are due to the required detection limits and the nature of the samples. When using alpha spectrometry to reach very low detection limits, critical technical hitches often arise because of the difficulties in separating radium from barium, in removing organics eluted from the separating chromatography column, and in plating radium. Moreover, overall chemical recovery of radium is often not reproducible, depending on the studies. Here we propose a method that separates radium from other alkaline-earth cations using cation exchange chromatography and selective complex formation by EDTA and DCTA. Radium is completely free of the ²²⁹Th tracer and its daughter products, particularly ²²⁵Ac. Organics from the column are removed in a further purification step so that radium can be plated with acceptable yields in a HCl/HNO₃/ethanol solution. We successfully applied the method to soil, water, urine and human bone samples and further extended it to the determination of ²²³Ra in a bone biopsy, using ²²⁶Ra as an internal tracer.

Preliminary investigations on reducing the high radiation risk level of TENORM scale waste from petroleum industry

The main objective of this study is directed to remove 226Ra, 228Ra radionuclides from TENORM scale waste without seriously degradation the physicochemical characteristics of soils or generating waste. It was found that 82, 87% removal of total radioactivity using successive washing by commercial and TX-100 solutions, respectively, after seven cycles. Some radiation risk before and after treatment with surfactants were determined. It is a promising and efficient as well as economic process. Our results from this task could provide a useful information for defining the establishing and operating on a pilot-scale plant for efficient and economic TENORM treatment.

Variance in State Protection from Exposure to NORM and TENORM Wastes Generated During Unconventional Oil and Gas Operations: Where We Are and Where We Need to Go

Radioactive materials for the medical, technological, and industrial sectors have been effectively regulated in the United States since as early as 1962. The steady increase in the exploration and production of shale gas in recent years has led to concerns about exposures to Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) in oil and gas waste streams. This study applied policy surveillance methods to conduct a cross-sectional fifty-state survey of law and regulations of NORM and TENORM waste from oil and gas operations. Results indicated that seventeen states drafted express regulations to reduce exposure to oil and gas NORM and TENORM waste. States with active oil and gas drilling that lack regulations controlling exposure to NORM and TENORM may leave the public and workers susceptible to adverse health effects from radiation. The study concludes with recommendations in regard to regulating oil and gas NORM and TENORM waste.

Investigation of chemical composition and moisture content for different materials on the attenuation of γ rays

In the present work, materials, namely mud, sand mud, ferruginous sandstone and sandstone with different densities are used to evaluate the effect of chemical composition and moisture content on the self-attenuation coefficient factor at γ-energy range from 59.5 to 1332.5 keV. The results revealed that the attenuation coefficient increases with increasing the moisture content until the material saturate with moisture. The average value of increasing linear attenuation coefficients based on increasing moisture content are 14.3%, 16.0%, 18.2%, 28.1% and 24.8% at γ-energies 59.5, 356.0, 661.7, 1173.4 and 1332.5 keV, respectively. Chemical composition of material affected on the values of attenuation, i.e. the elements with high density have high attenuation coefficient. Significant effect of self-attenuation correction factor was observed at low γ-energies up to 500 KeV. Application of the calculated correction of environmental sample with low radioactivity content has been carried out.