|
|
| Fig. 1: An ISL field in South Australia. (Source: Wikimedia Commons) |
Uranium mining is an essential part of nuclear energy worldwide. Mines all over the globe employ a variety of techniques in order to extract uranium oxide (U3O8), which is then milled into a uranium concentrate in the form of a yellow or brown powder. That powder can then be fabricated or enriched into fuel, which is used in nuclear reactors and power plants. In the United States alone in 2014, uranium mines produced 4.9 million pounds of uranium oxide, and milled 4.9 million pounds of uranium concentrate as well. [1]
Uranium mining operations make use of several different techniques and mine structures in order to extract the ore. Two classic setups, common in all sorts of mining, are pit mines and underground mining operations. In pit mines, a large open pit is dug into hard rock in the ground and uranium is mined from this pit. If the uranium ore is too deep for this technique, more traditional underground mine shafts are used. Another major technique for uranium ore extraction is that of in-situ leaching (ISL), where a solution is pumped into the ground to dissolve the minerals while underground. Then, the solution with the dissolved uranium mineral is pumped up to the surface and the ore can be recovered from solution. ISL is much less disruptive to the surface topography, since it does not require large holes or underground structures. [2] This minimal impact on the landscape can be seen in Fig. 1.
As with most widespread mining operations, there are important considerations with regards to the environmental impact of uranium mining. In a report published in the American Chemical Society Environmental Science & Technology journal, Gavin M. Mudd and Mark Diesendorf explored these considerations. Mudd and Diesendorf concluded that "the extent of economically recoverable uranium, although somewhat uncertain, is clearly linked to exploration effort, technology, and economics but is inextricably linked to environmental costs such as energy, water, and chemicals consumption, greenhouse gas emissions, and broader social issues." [3] They also found a link between ore grade (%U3O8) and greenhouse gas emissions - extracting lower-grade ore resulted in substantially more greenhouse gas emissions. They also note that in the medium- to long-term, available ore grade will gradually decline.
Among the "broader social issues" that Mudd and Diesendorf alluded to are the potentially adverse health effects of uranium mining and extraction. The Committee on Uranium Mining in Virginia documented some of these aspects that extend beyond the normal mining occupational hazards in Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. According to the Committee, the main risk inherent in uranium mining is exposure to radon, its decay products, and other radionuclides. These materials can lead to radiation exposure, both external and internal (a cut or ingestion) via alpha, beta, or gamma emission. A major complication that can arise from such exposure is a marked increase in one's risk for lung cancer. Further, there is a risk of exposure to radon or other radioactive materials in the surrounding environment - material can leach into drinking water, and there is particular potential for inadvertent exposure in case of an extreme event like a fire, earthquake, or flood. [4]
Historically, one group that was affected by the sorts of health risks outlined here were the Navajo people in mines in Rocky Mountain states. When more and more uranium fields were discovered beginning in the late fifties, Navajo men began to be employed as uranium miners. They were paid poorly, but gravitated toward the job as it was one of a limited selection of employment opportunities in the time and area through the mining boom of the 1970s. [5] Studies carried out after the fact on the Navajo miners found the same marked increase in cases of lung cancer, which was particularly noteworthy since the Navajo people did not smoke. [6] Despite the correlation being known as early as the 1930s, little was done to educate or dissuade would-be miners. [5]
Looking forward, the future trends in uranium mining seem to be largely downward ones. As previously stated, Mudd and Diesendorf anticipate uranium ore becoming lower and lower grade over time, and with that will come an increase in greenhouse gas emissions. [3] This is perhaps one factor that is depressing demand for uranium mining; another is the 2011 disaster at Japan's Fukushima plant. Spot prices for uranium have been down since that incident; large multinational uranium mining operations such as Areva and Cameco have been wary to expand as quickly as they could and in some cases have downsized. [7] However, Cameco is still considering an expansion down the line. As public wariness toward nuclear power mellows and larger-scale disasters such as Fukushima drift farther into the past, demand for nuclear power may well rise once more, and that is what Cameco is potentially anticipating. [8] In the U.S., the United States Forest Service rejected a proposal to build a new uranium mining site near the Grand Canyon. When considering America's existing uranium reserves, it's easy to see how uranium mining may become less prevalent. [9]
© Greg Ramel. 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] "2014 Domestic Uranium Production Report," U.S. Energy Information Administration, April 2015.
[2] "Manual of Acid in Situ Leach Uranium Mining Technology," International Atomic Energy Agency, IAEA-TECDOC-1239, August 2001.
[3] G. M. Mudd and M. Diesendorf, "Sustainability of Uranium Mining and Milling: Toward Quantifying Resources and Eco-Efficiency," Environ. Sci. Technol. 42, 2624 (2008).
[4] Uranium Mining in Virginia (National Academies Press, 2012).
[5] D. Brugge and R. Goble, "The History of Uranium Mining and the Navajo People," Am. J. Public Health 92, 1410 (2002).
[6] J. M. Samet et al., "Uranium Mining and Lung Cancer in Navajo Men," N. Engl. J. Med. 310, 1481 (1984).
[7] R. Nickel, "Uranium Miners Cautious on New Output, Despite Forecast Shortfall," Reuters, 8 Mar 16.
[8] R. Nickel, "Cameco Slowly Expands World's Biggest Uranium Mine, Betting on Recovery," Reuters 7 Mar 16.
[9] B. C. Howard, "U.S. Government Says 'No' to Grand Canyon Project," National Geographic, 7 Mar 16.
