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Operation and decommissioning of uranium mines

Uranium, an element found in the Earth’s crust at an average concentration of 3 ppm (parts per million), is extracted primarily from open pit and underground mines, and today more and more commonly by leaching, also called ISR (for in-situ recovery). The financial viability of a deposit depends on many parameters, including the quantity and grade of the ore and the geographic location, geological configuration and depth of the seam(s), as well as environmental, economic and political considerations. Uranium ores can contain concentrations ranging from a few hundred ppm to 195 kilograms of uranium per ton for the McArthur River Mine in Saskatchewan, Canada. Today the most productive mines are located in Canada, Kazakhstan, Australia, Namibia, Russia and Niger. In 2010, those six countries supplied 54% of the world’s uranium production. The fissile isotope U-235, found in natural uranium at a concentration of only 0.7%, is a rare, precious resource.
In France, uranium was extracted between 1945 and 2001 from 210 mines in 25 départements (administrative regions), mostly located in the central part of the country. About 52 million tons of uranium ore were processed over that period, yielding 76,000 tons of uranium.
Because most of France's ore contains very little uranium and is extracted from mines distant from any nuclear site, shipping the ore is not economically viable and it must be processed on site. Mined ore is ground into a fine powder and then chemically treated to dissolve and extract the uranium. In the case of in-situ leaching, an acid solution is injected directly into the ground through a borehole and retrieved through another borehole.
A uranium mine generates many types of wastes: atmospheric emissions (including radon, a highly toxic gas emitted by the ore itself), liquid wastes, solid wastes (sludge, etc.), waste rock containing very little uranium, which is not processed but stored outside the mine, and finally, ores with a low uranium content, which are also stored. Because these different types of waste can contaminate the environment and pose a potential threat to local populations, the entire extraction process must be carefully controlled, as well as the decommissioning of the mines once they are depleted. In France, CNRS laboratories, working in association with the Becquerel network, regularly monitor the levels of radioactivity in the soil and water near uranium mines in order to analyze the risk of groundwater contamination and address the issues linked with waste rock storage. Studies on the management of long-term risks are conducted with the help of CNRS researchers in the humanities and social sciences.
The public is kept informed through France’s Local Information Commissions (CLI), which involve other organizations like the IRSN (French Institute for Radiological Protection and Nuclear Safety) and CRIIRAD (Commission for Independent Research and Information on Radioactivity). IRSN and CRIIRAD also perform their own analyses.