Uranium mining methods
Conventional mining means that ore in solid form is removed from the ground and processed at a mill to extract the uranium. There are essentially two types of conventional mining: surface (open pit) and underground. The depth at which ore is buried determines whether producers will use surface or underground mining.
Deposits occurring within about 300 feet of the surface can usually be mined by open pit methods, while deeper deposits require underground extraction. Geologists and mining engineers work collaboratively to develop efficient, economic plans for mining uranium ore. Chemical engineers devise ways to extract the uranium from the ore at minimal cost and impact to the environment.
In-situ mining (ISR or ISL)
Unlike conventional mining methods, in-situ recovery removes the uranium from its host rock, and leaves the rock in place. This process involves pumping an environmentally benign solution of water and sodium bicarbonate and/or gaseous carbon dioxide and oxygen down an injection well, where it flows through the existing aquifer to the ore deposit, dissolving the uranium. The fluid containing the leaching agents is known as lixiviant or leachate. The uranium-rich lixiviant is then pumped back to the surface through extraction wells and the uranium is extracted from solution at a central processing facility. The lixiviant solution is recycled. In-situ mining produces no tailings and has significant operational and environmental advantages over conventional mining.