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| Fig. 1: Distribution of annual radon progeny values in WLM per year for the four most frequent job activities in the milling facility "Crossen, 101" as estimated by the job exposure matrix. [4] The WLM is an exposure measure that is the product of (1) the number of months of exposure (2) the working level. A working level of "one" is defined to be any combination of short-lived radon progeny in 1 liter of air that results in ultimate emission of 130,000 MeV of energy from α particles. The energy of an α particle is typically 4 MeV, so a working level of "one" means 3.25 × 104 α particles are eventually generated from each liter of air. (Source: M. Chang, after Kreutzer et al. [4]) |
Nuclear energy promises to be a more clean form of energy than traditional fossil fuels with a lower environmental impact than coal or natural gas, as there is no greenhouse gas emitted from its use. However, the generation of any type of natural energy resource requires harvesting that resource from the earth, and Nuclear energy is no exception. The process of harvesting and processing Uranium often comes under public scrutiny as Nuclear energy and radioactive materials are often touchy subjects for the public. Historically, there have been incidents where pollutants from these processes have contaminated the environment, however, in the present day, there is little to no risk of Uranium mines or milling plants polluting the environment.
Open-Pit: Open-pit or open-cut mining is the process most typically used when the orebodies lie close to the surface. The overlying rock and dirt are removed (most typically with explosives) to expose the ore, resulting in a large open pit.
Underground: Underground mining is performed when the ore bodies lie too deep in the earth to feasibly perform open- pit mining. This process is the closest to (metalliferous) mining which most readers will be familiar with and consists of constructing deep access shafts and tunnels. This process is much more dangerous and time-intensive than open-pit mining but in return displaces less topsoil and results in fewer waste materials.
In-Situ Leach (ISL): In-Situ mining is a relatively new process by which uranium, which is in groundwater in porous material, is extracted from the ground without first bringing the ore to the surface. Leaching solution, a weakly acidified water, is pumped through the aquafer, dissolving the Uranium before being pumped to the surface where the Uranium is recovered.
Heap Leaching: Unlike traditional leaching where ore is first processed into a powder to extract the minerals, heap leaching is the process of uranium extraction by stacking ore 5 to 30 meters high on an impermeable mat and irrigating the "heap" with acid or alkaline.
Acid/Alkaline Leaching: In this more traditional form of leaching, Uranium ore is first treated, sometimes by "roasting", burning off excess waste material, or grinding the ore into a powder. This processed ore is then treated with either acid or alkaline solution to aid in the extraction of Uranium.
All mining processes produce "tailings" or waste products. However, in the case of Uranium mines, these tailings are radioactive and if not properly disposed of could have serious effects on the air, water, and land quality of the surrounding environment. [1] Additionally, in the case of open-pit mining, the displacement of topsoil can result in polluted water and groundwater as well as increased erosion and chances of landslides. [2]
In general Uranium mining does not have any additional adverse effects on the people working at the mine when compared to other metalliferous mining. While those who work in the mines are exposed to some small level of radiation above natural levels of exposure, this amount is so small as to be inconsequential. There are very strict regulations on acceptable levels of exposure and Geiger counters are a simple tool to ensure that these restrictions are followed. A study conducted in Spain found that the Radon levels in a Uranium mine were measured for an average of 150 bq m^3 between 2 and 10 times less than that of tourist caves open to the public. [3]
However, in the uranium extraction process, workers at mills can be exposed to uranium and silica dust, which has been positively linked to increased rates of lung cancer. [4] As can be seen in Fig. 1. All jobs in Uranium mills experienced increased exposure to Radon.
The majority of health effects impacted workers operating milling stations for Uranium extraction. These are only necessary for ore-extracting forms of mining and in-situ leaching can eliminate the need for these milling factories, though the conditions for this process need to be precise.
Additionally, the environmental impacts of Uranium mining can be minimized if the tailings are properly disposed of and or treated. One potential solution for the tailing immobilization is a "tailing dam", a large body of water cordoned off for use as tailing storage. The water can then be released back into the environment after sufficient chemical treatment if and when the dam is decommissioned. [5] This is just one example of a waste immobilization technique.
While radioactive tailings can seriously damage the environment if mishandled, with proper care uranium mines can have the same health impact and a lower environmental footprint than those of traditional coal or natural gas mining methods.
© Michael Chang. 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] X. Longstaff, "The Health and Environmental Impact of Uranium Mining," Physics 241, Stanford University, Winter 2017.
[2] "Managing Environmental and Health Impacts of Uranium Mining, Nuclear Energy Agency, No. 7062, 2014.
[3] L. Quindós Poncela et al., "Radon Exposure in Uranium Mining Industry vs. Exposure in Tourist Caves", Radiat. Prot. Dosimetry 111, 41 (2004).
[4] M. Kreutzer et al., "Mortality from Internal and External Radiation Exposure in a Cohort of Male German Uranium Millers, 1946-2008," Int. Arch. Occup. Environ. Health 88, 431 (2015).
[5] H. M. Fernandes et al., "Management of Uranium Mill Tailing: Geochemical Processes and Radiological Risk Assessment," J. Environ. Radioact. 30, 69 (1996).