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| Fig. 1: The Jackpile Mine in New Mexico is a 3000 acre open-pit uranium mine. (Source: Wikimedia Commons) |
With the continued threat of climate change and its irreversible consequences imminent, clean and sustainable energy is a goal shared by much of the world. While nuclear energy remains a polarizing topic, it is appealing due to its high energy density. U-235 has an energy density of 2.36 × 104 MWh/kg which is equivalent to 8.48 × 107 MJ/kg. [1] A kilogram of uranium metal from the ground, which is .72% fissile U-235, therefore has energy content of 6.11 × 105 MJ. In comparison, bituminous coal has an energy density of 26.9 MJ/kg. [2] Dividing the two numbers, one finds that 22,700 kg - or 22.7 tons - of coal are required to produce the same energy as 1 kg of uranium metal out of the ground. As a result of this high energy content, most modern countries, including the U.S. and France, rely on nuclear energy to fulfill military and civil demands. [3] The widespread use of nuclear energy can be seen in Table 1, which shows its share of electricity production in various countries. The usage and demand for nuclear energy necessitates large-scale uranium production via uranium mining, a process that poses significant environmental, social, and health hazards. Whether the benefits of nuclear energy offset these consequences needs to be carefully examined when assessing the future of nuclear energy.
Uranium is most commonly extracted from the earth using the methods of open-pit mining, underground mining, and in-situ leach mining. Each mining method poses unique environmental consequences.
In open-pit mining, rocks and soil are removed to expose and access the underlying uranium ore. These mines span hundreds to thousands of acres, as seen in Fig. 1. [4] For each ton of ore processed via open-pit mining, 40 tons of waste are generated, and dust and radon gas are released during this process. The excavated waste rock, which contains radioactive residue, is deposited into to large waste piles that can become unstable and cause landslides. [3]
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| Table 1: Share of electricity production from nuclear energy in 2019, by country. [10] |
In underground mining, mine shafts are drilled into ore beds. Workers are exposed to high levels of radon, so a large amount of water is used to mitigate the release of radon. However, with the additional risks of collapse, fire, flood, and pneumoconiosis, underground mining poses the most health hazards to laborers. [3,5]
In-situ leaching involves the injection of a lixiviant - commonly sulfuric acid - into the earth at mining locations. The lixiviant interacts with the ores and leaches out an impure mixture of uranium that is collected, and the uranium is later extracted and purified. This method of uranium collection minimizes air contamination but has greater potential for water contamination when the lixiviant mixes with underground water. The water pollution can lead to the presence of sulfuric acid in downstream ecosystems. [3]
In order to convert the extracted uranium to a usable form, the uranium undergoes a process known as milling. This consists of crushing the uranium ore into a fine sand and using a lixiviant to further separate and purify the uranium into its usable form, known as "yellow cake". The radioactive rock and sand byproducts of this process are called tailings. The residual rock waste is placed into a pile, while finer dust residue is mixed with water, and the slurry is placed into in tailing ponds. Tailings are one of the primary sources of health and environmental concerns in the context of uranium extraction. [3]
Tailing deposits can cause landslides, air contamination, and wildlife exposure. Uranium tailings contain small particles that are picked up and transported by the wind. The radioactive particulates in the air can be concentrated enough to cause health issues including lung cancer and kidney disease. [6] These particles also contaminate soil and water. Furthermore, growing piles of mining debris become unstable and can result in fatal landslides, such as the 1966 landslide of Aberfan, which resulted in the death of 144 people. [7] Tailing ponds pose serious hazards to the environment as well through leaks, in which underground water becomes contaminated with heavy metals. [5] This can lead to the pollution of lakes and rivers. Local ecosystems, too, are harmed and destroyed by waste piles and ponds. Rain can interact with tailings and introduce sulfuric acid in aquatic ecosystems, similar to in-situ leaching. Wildlife exposure can also occur directly through interaction with tailing ponds. In particular, waterfowl often land and use tailing ponds, resulting in dire consequences. In 2008, 1600 ducks flew into a tailing pond and died in Alberta, Canada. [8] Evidently, the repercussions of uranium mining are far-reaching. Certain groups of people, however, are at greater risk of exposure to associated hazards.
The United States has a history of environmental inequity in which people of color and low-income communities are disproportionately subjected to environmental risks and consequent health hazards. Uranium mining is no different. Navajo Nation land, for example, is littered with tailing piles, and the United States Environmental Protection Agency has mapped 521 abandoned uranium mines on the reservation. [5,9] In this regard, uranium mining serves as an avenue for continued environmental racism, and the issue demands close examination and public awareness.
The world is rapidly approaching the point of no return in which the consequences of climate change cannot be reversed. With its high energy density and promise as a sustainable and clean source, nuclear energy is undoubtedly an appealing and feasible alternative during a time of great urgency. The long-term effects of nuclear energy on the environment and human health must carefully be considered, however. As the demand for uranium grows, so too do the hazards associated with uranium mining. Do the benefits of nuclear energy outweigh the risks of air and water pollution, and consequent illness, destroyed ecosystems, and injured wildlife? The search for clean energy stems from the desire to protect and preserve the earth, but uranium poses threats that seemingly accomplish the opposite. The consequences of nuclear energy must therefore be carefully assessed and considered when regarding its future.
© Rochelle Radzyminski. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] O. Eriksson, "Nuclear Power and Resource Efficiency - A Proposal for a Revised Primary Energy Factor," Sustainability 9, 1063 (2017).
[2] N. F. Mohamad et al., "Characteristics of Bituminous Coal, Sub-Bituminous Coal and Bottom Ash From a Coal-Fired Power Plant," IEEE 6560193, IEEE Business Engineering and Industrial Applications Colloquium (BEIAC), Langkawi, Malaysia, 7 Apr 13, pp. 571-573.
[3] R. R. Srivastava, P. Pathak, and M. Perween, "Environmental and Health Impact Due to Uranium Mining," in Uranium in Plants and the Environment, ed. by D. Gupta and C. Walther (Springer, 2020).
[4] G. H. Fettus and M. G. McKinzie, "Nuclear Fuel's Dirty Beginnings," Natural Resources Defense Council, March 2012.
[5] X. Longstaff, "The Health and Environmental Impact of Uranium Mining," Physics 241, Stanford University, Winter 2017.
[6] D. Dewar, L. Harvey, and C. Vakil, "Uranium Mining and Health," Can. Fam. Physician 59, 469 (2013).
[7] S. Rybalchenko, K. Verhovov, K., and S. Kudriavtcev, "Landslides-Flows on Rock Dumps of Coal Mining Enterprises," MATEC Web Conf 265, 04010 (2019).
[8] M. Sutton, "Discourses of the Alberta Oil Sands: What Key Stakeholders Really Think About Sustainability," Consilience 18, 175 (2017).
[9] C. Arnold, "Once Upon a Mine: The Legacy of Uranium on the Navajo Nation," Environ. Health Perspect. 122, A44 (2014).
[10] "BP Statistical Review of World Energy 2020," British Petroleum, June 2020.
