Processing: from ore to “yellow cake”
Once uranium ore has been extracted in an underground or open-pit mine, it is transported to a processing plant. This step allows us to obtain concentrated uranium, or "yellow cake".
Purification and concentration of uranium ore
Once the ore has been removed from the mine, it is processed in one of the following ways, depending on its grade:
High-grade ore (uranium content > 0.10%) is transported to a processing plant, where it is
- crushed and ground mechanically
- processed and purified with chemical solutions
- extracted from the resulting liquor using organic solutions or ion exchange resins
- washed and filtered
- precipitated and dried.
Acid heap leaching
SOMAÏR has been using this modern method for the extraction of uranium from low-grade ores ( < 0.10%) since 2009. This process is called “heap” leaching because the ore is stacked up. It is the first time that leaching has been used in uranium mining. The steps in the process are as follows:
- The ore is crushed to reduce it to particles of appropriate size
- The particles are aggregated in an agglomerator using water and acid to enhance the permeability and stability of the heaps.
- The ore is heaped up by stackers at the leach pads
- An acid solution percolates through the ore heap for about 3 months
- The uranium-bearing solution drains from the heap and is collected. - The uranium is extracted from the solution using a solvent in a chemical treatment plant.
After drying, a solid, concentrated uranium is obtained called "yellow cake" (due to its color and its doughy texture at the end of the procedure) containing around 75% uranium, or 750 kilograms per metric ton.
The "yellow cake" is packaged and put into barrels, then sent to conversion facilities for further chemical processing.