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| Fig. 1: World energy consumption by energy source; 1990-2040. [1] (Courtesy of the U.S. Energy Information Administration) |
Nuclear is an efficient and powerful energy source with life cycle carbon emissions that are as low as some renewable sources. While not as popular as liquid and coal, nuclear power plants still generate a significant portion of the world's energy. In 2014, for example, nuclear energy was responsible for 15% of the world's electricity despite the fact that only 30 countries reported having operational power plants. [1] Nuclear energy still remains controversial however, tainted by disasters like Fukushima and its history as a weapon of war.
Because of this complex history, the future of nuclear energy is difficult to predict and will depend on external factors including the prices of fossil fuels, environmental and climate considerations and energy policy. Still, most projections based on global and regional information about policy and nuclear technology such as the projection depicted in Fig. 1 predict an expansion in nuclear power over the next 30 years. [1]
In looking to the future of nuclear energy it is essential to consider, prepare for and regulate the potential impacts of this technology on the environment and human health. Currently most efforts in this vein focus on radiation protection and defenses at the reactors and processing facilities themselves. However, the process of obtaining Uranium through mining and processing ore also poses serious risks to people and the environment. To complicate these issues further, historically in the United States and around the globe the negative impacts of Uranium mining have fallen disproportionately on low income and minority communities. [2] Because of this history, it is important for agencies like the Nuclear Energy Agency and others to continue to promote the development of science and technology to improve the practices of Uranium mining to ensure the peaceful use of this energy and the safe disposal of its waste.
There are several extraction strategies employed in the mining of Uranium. The main types include:
Surface mining or open-pit mining depends on the removal of all surface soil and rock covering the desired Uranium. While it is safer for the miners than underground mines since they are not exposed to roof-falls or pneumoconiosis, it blasts 30 times more topsoil than Uranium ore and the resulting land is left with radioactive, toxic elements and increased erosion, landslides and pollution of the soil and water. [2]
Heap Leaching involves dissolution of minerals from crushed ore under percolating water and chemicals to generate metal salts in solvent phase that can then be separated and collected. These processes often employ Sulphuric Acid and Cyanic salts as lixiviants. While the popularity of this method has declined since the 1980's, it is still in use in some plants today. [3]
Underground mining requires drilling deep shafts into the ore bed. This technique employs water to prevent radiation exposure to laborers. [4] The ore deposits are brought to the surface and arranged in piles near the extraction points. Then, ore is processed into Uranium yellowcake and the waste is put into dumps. An overview of this process is shown in Fig. 2. This practice produces radioactive waste rock and exposes workers to more radioactive gases like radon than open-pit mines but produces less quantities of toxic tailings.
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| Fig. 2: Schematic of the Uranium milling process. [2,7] (Courtesy of the U.S. Energy Information Administration) |
Uranium mining facilities produce tailings that generally are disposed of in near surface impoundments close to the mine. These tailings pose serious environmental and health risks in the form of Randon emission, windblown dust dispersal and leaching of contaminants including heavy metals and arsenic into the water. [5] Historically in many countries around the world these risks have been politicized as they have disproportionately affected low income and minority populations. For example, from 1944-1986 the United States extracted 4 million tons of Uranium ore from and left 500 abandoned mines in native Navajo territories. In that time the rates of lung cancer and other diseases effecting Navajo living near the mine rose drastically. [5] While the Navajo eventually were able to ban mining on their land these problems still exist within other communities today and should not be overlooked in considering the future of Uranium mines.
Research has been seeking progress in the management of the waste and risks of Uranium mining. Historic strategies for treating Uranium mines have included capping to reduce radon emanation and reactions that promote leaching, and drainage systems to collect and remove harmful products. These strategies have not been extremely successful however and some practices like capping can cause additional environmental problems. Because of these deficiencies, regulating agencies have been calling for further research into the development of advanced barriers, capping with geochemical stabilization of waste as well as methods of restoring lands through remediation. These efforts have yielded some promising ideas. Some of the documented potential improvements for long term stabilization of Uranium mill tailings include new materials like room temperature ceramics for the immobilization of various contaminants, dewatering, backfilling and using residues for the construction of motorways. Other tested technologies used for remediation include soil washing with water, carbon treatment and land encapsulation. [6] This research into cleaner and safer mining practices points to the future of nuclear energy.
© Xochitl Longstaff. 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] "International Energy Outlook 2016," U.S. Energy Information Administration, DOE/EIA-0484(2016), May 2016, pp. 7-18.
[2] G. H. Fettus and M. G. McKinzie, "Nuclear Fuel's Dirty Beginnings," Natural Resources Defense Council, March 2012.
[3] C. Zanbak, "Heap Leaching Technique in Mining," Euromines, November 2012
[4] B. Weil, "Uranium Mining and Extraction from Ore," Physics 241, Stanford University, Winter 2012.
[5] C. Arnold, "Once Upon a Mine: The Legacy of Uranium on the Navajo Nation," Environ. Health Perspect. 122, A44 (2014).
[6] "Assessment of Technologies for the Remediation of Radioactively Contaminated Superfund Sites," U.S. Environmental Protection Agency, EPA/540/2-90/001, January 1990.
[7] "Decommissioning of U.S. Uranium Production Facilities," U.S. Energy Information Administration, DOE/EIA-0592, February 1995.