Did You Know?
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Ionizing radiation often enters the body through ingestion of contaminated materials. For more information, see: For a lesson about this topic, see: |
How do you find uranium deposits?
Today’s exploration activities are much more complex than in the past when the deposits that were close to the surface were first discovered. With the highest-grade deposits buried in deep rock formations, advanced technologies such as satellite imagery, geophysical surveys, multi-element geochemical analysis and computer processing are required to locate and confirm the deposits.
Once geologists locate a prospective deposit, detailed geological and economic evaluation of the grade and characteristics of the orebody must be completed. Then mining engineers develop a mining plan to extract the ore. If the project looks promising, environmental impact assessments and the public consultation process begin so that applications can be made for regulatory approvals of project development. When permits and licences are in place, mine development and construction of surface facilities can begin. The timeline from discovery of an orebody to electricity production can span decades. Cameco’s McArthur River mine was fast-tracked and still took 12 years to bring to commercial production.
At Cameco Corporation, uranium exploration has focused in recent years on targets in northern Saskatchewan’s Athabasca Basin and Arnhem Land in the Northern Territory of Australia.
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| Cameco's Key Lake mine in 1994. The photo on the top is an aerial view of Deilmann Pit. On the bottom ore is being loaded onto a truck to be transported to the surface. After mining was completed in 1996, the pit was converted to a tailings storage facility |
Open Pit Mining
When uranium ore is found near the surface, generally less than 100 metres deep, it is typically extracted by the open pit mining method. Open pit mining begins by removing overburden (soil) and waste rock on top of the orebody to expose the hard rock. Then a pit is excavated to access the ore. The walls of the pit are mined in a series of benches to prevent them from collapsing. To mine each bench, holes are drilled into the rock and loaded with explosives, which are detonated to break up the rock. The resulting broken rock is then hauled to the surface in large trucks that carry up to 200 tonnes of material at a time.
Underground Mining
For economic reasons, when an orebody is located more than 100 metres below the surface, underground mining methods are necessary rather than mining by open pit. For example, Cameco’s McArthur River orebody is located more than 500 metres below the surface so it is mined using an underground mining method.
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| Mine operator Ken Pederson uses a remote controlled scoop tram to collect and transport uranium ore 640 metres underground at McArthur River, the world's largest, highest grade uranium mine. |
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| Cross-section of McArthur River underground development |
The first step in underground mining is to access the ore. Entry into underground mines is gained by digging vertical shafts to the depth of the orebody. Then a number of tunnels are cut around the deposit. A series of horizontal tunnels, called drifts, offer access directly to the ore and provide ventilation pathways. All underground mines are ventilated, but in uranium mines, extra care is taken with ventilation to minimize the amount of radiation exposure and dust inhalation.
In most underground mines the ore is blasted and hoisted to the surface for milling. At McArthur River, due to the potential for radiation exposure from the high-grade ore, processing systems must ensure worker safety. As a result, the ore is processed underground to the consistency of fine sand, diluted with water and pumped to the surface as slurry or mud. The slurry is trucked to the Key Lake site for milling.
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| Mining at Smith Ranch-Highland uses an environment-friendly extraction method called in situ recovery (ISR) |
In Situ Recovery
In a few places geological conditions allow uranium to be dissolved directly by pumping mining solutions underground, bringing it back to the surface, and extracting the dissolved uranium. With this in situ recovery (ISR) process there is limited surface environmental disturbance. "In situ" means in the original position or place. The surrounding rock remains in place while the dissolved uranium is pumped to the surface then circulated through a processing plant for extraction. ISR is suitable for certain deposits such as Cameco’s US operations and is the mining method at the Inkai project in Kazakhstan.
Source:Cameco Corporation, Uranium 101, www.cameco.com/common/pdfs/uranium_101/U101.pdf