At the mill, uranium ore undergoes a variety of changes to turn it into a finished product: uranium powder, also known as yellowcake.
The milling process is so important that the U.S. Atomic Energy Commission has helped mines establish mills close by to make it easier to process uranium ore and quicken the production of yellowcake [source: Amundson].
For dry uranium ore, the rocks are milled up into smaller pieces before being placed in tanks. In-situ recovery solutions are usually ready to be placed in tanks as well. Depending on how the uranium was mined, chemical solutions are applied to the ore to strip other substances away. One part of the process will separate sand and debris gathered with the ore through ion technology, while another will use a series of solvents to pick the uranium away from other parts of the ore. Throughout the milling process, remnants of other rocks and radioactive elements from the ore -- also called tailings -- are gathered to be stored away. The product will continue to undergo chemical separation until all that's left is the desired amount of uranium.
The goal is to isolate uranium oxide (U3O8) to sell to companies for further enrichment. Most milling operations employ between 20 and 50 people [source: Hunter].
After milling, other companies will buy the uranium to enrich it, or increase the ratio of the isotope U-235 in a given sample. During enrichment, scientists convert the yellowcake (uranium oxide) to uranium hexafluoride gas, which is put in cylinders to become a solid when it cools [source: NRC]. To enrich uranium enough to be used as nuclear fuel, workers will increase the concentration of U-235 in the sample to usually between 2 and 5 percent [source: Nuclear Energy Institute]. Then, fuel fabricators will transform the substance into uranium oxide powder to be compressed into uranium fuel pellets. The enriching process is highly regulated and is often done by companies other than the ones that mined it.
The effects of uranium mining span beyond the mine. Learn more about the activity's impact on human health next.