Transition from NORM to TENORM
Oil and gas deposits contain naturally-occurring radionuclides, such as the 238U series, 232Th series and 40K, which have been identified as Naturally Occurring Radioactive Materials, abbreviated as ‘NORM’ (Attallah et al., 2020). The operation of oil and gas equipment involves the precipitation of alkaline earth metals such as sulfates, carbonate and silicates, resulting in the production of TENORM (Abdelbary et al., 2019). The radionuclides produced by the aforementioned isotopes and their decay products then often end up either dissolved or suspended in produced water, resulting in various forms of waste such as sludge, mineral scales, and thin-films (El Afifi et al., 2023).
Fig. 1: Presence of naturally-occurring radionuclides in oil and gas deposits, and the equipment and processes involved in oil and gas production (Source: Ali et al., 2019).
Radioactivity of TENORM wastes
Current literature posit that TENORM wastes contain radioactive concentrations of Ra-226 levels significantly higher than what is permitted by the International Atomic Energy Agency (IAEA) (Hilal et al., 2014). Due to its extremely long half-life and high abundance of its parent nuclide (238U), 226Ra remains as the superabundant radium isotope found on TENORM wastes (Attallah et al., 2019). Similar to the nature of phosphogypsum discussed in the previous blog article, these TENORM wastes resulting from oil and gas processing also give rise to the generation of radon gas, which produces alpha particles as it decays (Attallah et al., 2019). According to Alfifi et al (2023), the radiological hazard parameters of scale and sludge residues and produced water—specifically pertaining to 222Rn levels—have been found to exceed well beyond the allowed safe limits.
Public exposure to TENORM wastes can occur through direct exposure pathways or through inhalation and ingestion from contaminated soil and water sources arising from the disposal of TENORM wastes (ALNabhani et al., 2016). In light of this, the International Atomic Energy Agency (IAEA) has put forth safety standards for industrial activities which involve NORM, specifically with regard to radiation protection and radioactive waste management for the oil and gas industry (Ali et al., 2021). Unfortunately, these proposed safety standards are inadequate at reducing radiation exposure risks, with current TENORM waste disposal methods often exacerbating the distribution of radionuclides and their decay products. ALNabhani et al (2017) posit that waste products from oil and gas production—of which contain varying levels of TENORM—are often disposed of above ground or underground, exposing workers to radiation. An elaboration of these disposal methods are illustrated in the figure below:
Fig. 2: TENORM waste disposal methods used in the oil and gas industry (Source: ALNabhani et al., 2017)
Lack of management strategies
While the presence of TENORM in wastes generated by the oil and gas industry is not a new discovery, there is still insufficient research and understanding on the impacts of TENORM on public health and safety (ALNahbani et al., 2016). Furthermore, while the IAEA has proposed recommended measures, the implementation of these measures vary across governing bodies, and there is still an absence of a standardised set of regulations with regard to TENORM management and disposal (Ault et al., 2014).
In the US, sludge containing TENORM contents is first dewatered and stored in tanks for later disposal, while produced waters are injected into deep wells, and scale is sandblasted with water, and the removed scale is then stored in drums for later disposal (US Environmental Protection Agency, 2015). Elsewhere, the open dumping of produced water is legal in Brazil, and for several European countries as well (Landa, 2007).
References
Abdelbary, H. M., Elsofany, E. A., Mohamed, Y. T., Abo-Aly, M. M., & Attallah, M. F. (2019). Characterization and radiological impacts assessment of scale TENORM waste produced from oil and natural gas production in Egypt. Environmental Science and Pollution Research, 26(30), 30836–30846. https://doi.org/10.1007/s11356-019-06183-x
AL Nabhani, K., Khan, F., & Yang, M. (2016). Technologically Enhanced Naturally Occurring Radioactive Materials in oil and gas production: A silent killer. Process Safety and Environmental Protection, 99, 237–247. https://doi.org/10.1016/j.psep.2015.09.014
Ali, M. M. M., Li, Z., Zhao, H., Rawashdeh, A., Al Hassan, M., & Ado, M. (2021). Characterization of the health and environmental radiological effects of TENORM and radiation hazard indicators in petroleum waste –Yemen. Process Safety and Environmental Protection, 146, 451–463. https://doi.org/10.1016/j.psep.2020.11.016
Ali, M. M. M., Zhao, H., Li, Z., & Maglas, N. N. M. (n.d.). Concentrations of TENORMs in the petroleum industry and their environmental and health effects. RSC Advances, 9(67), 39201–39229. https://doi.org/10.1039/c9ra06086c
ALNabhani, K., Khan, F., & Yang, M. (2016). The importance of public participation in legislation of TENORM risk management in the oil and gas industry. Process Safety and Environmental Protection, 102, 606–614. https://doi.org/10.1016/j.psep.2016.04.030
ALNabhani, K., Khan, F., & Yang, M. (2017). Management of TENORMs produced during oil and gas operation. Journal of Loss Prevention in the Process Industries, 47, 161–168. https://doi.org/10.1016/j.jlp.2017.03.016
Attallah, M. F., Abdelbary, H. M., Elsofany, E. A., Mohamed, Y. T., & Abo-Aly, M. M. (2020). Radiation safety and environmental impact assessment of sludge TENORM waste produced from petroleum industry in Egypt. Process Safety and Environmental Protection, 142, 308–316. https://doi.org/10.1016/j.psep.2020.06.012
Attallah, M. F., Hamed, M. M., & El Afifi, E. M. (2019). Remediation of TENORM scale waste generated from petroleum industry using single and mixed micelles solutions. Journal of Molecular Liquids, 294, 111565. https://doi.org/10.1016/j.molliq.2019.111565
Ault, T., Krahn, S., & Croff, A. (2015). Radiological Impacts and Regulation of Rare Earth Elements in Non-Nuclear Energy Production. Energies, 8(3), Article 3. https://doi.org/10.3390/en8032066
El Afifi, E. M., Mansy, M. S., & Hilal, M. A. (2023). Radiochemical signature of radium-isotopes and some radiological hazard parameters in TENORM waste associated with petroleum production: A review study. Journal of Environmental Radioactivity, 256, 107042. https://doi.org/10.1016/j.jenvrad.2022.107042
Hilal, M. A., Attallah, M. F., Mohamed, G. Y., & Fayez-Hassan, M. (2014). Evaluation of radiation hazard potential of TENORM waste from oil and natural gas production. Journal of Environmental Radioactivity, 136, 121–126. https://doi.org/10.1016/j.jenvrad.2014.05.016
Landa, E. R. (2007). Naturally occurring radionuclides from industrial sources: Characteristics and fate in the environment. In G. Shaw (Ed.), Radioactivity in the Environment (Vol. 10, pp. 211–237). Elsevier. https://doi.org/10.1016/S1569-4860(06)10010-8
US EPA, O. (2015, April 22). TENORM: Oil and Gas Production Wastes [Overviews and Factsheets]. https://www.epa.gov/radiation/tenorm-oil-and-gas-production-wastes