Nuclear Energy Insight
May 2009—This is the first in a series of articles that will demystify nuclear technology.
Uranium is a common element found in the earth’s crust, about as abundant as tin.
Uranium is mined where there are concentrations in the earth’s crust. More than half of the world’s uranium comes from mines in Canada, Australia and Kazakhstan. Other major producers are the United States, South Africa, Namibia, Brazil, Niger and Russia. Many more countries have smaller deposits that could be mined if needed.
Most U.S. uranium mines use a process called in-situ leaching, which dissolves the mineral from the ore deep in the mine and then pumps it to the surface. A process called milling then extracts the uranium and concentrates it to an oxide, U3O8, which is shipped from the mine and sold as “yellowcake.”
In-situ leach (ISL) mining causes much less environmental disturbance than conventional open-pit mining.
The ore remains in the ground, and the uranium minerals are recovered by simply dissolving them underground and pumping the resultant solution to the surface. There is very little surface disturbance—the only visible evidence is a series of boreholes.
The process generates no waste rock or mill tailings requiring long-term management.
An ISL mine typically has a useful production life of one to three years, with an average recovery of 60 percent to 80 percent of the ore. Rehabilitation of a used mine is much easier than conventional pit mines. After the wells are sealed or capped and the processing equipment removed, the land can readily be returned to its former or new uses.
The major consideration with ISL mining is to avoid the contamination of any nearby groundwater by the solution injection or withdrawal processes. This is ensured by testing prior to commissioning of the mine, and treatment after decommissioning if necessary.
—Read more articles in Nuclear Energy Insight and Insight Web Extra.