When the natural uranium is mined from underground and open pit mines, it consists of 99.3 U238 and only 0.7 of U235. The extracted ore goes through the ordinary mineral dressing processes crushing, grinding, screening, flotation, and gravity separation to increase the U235 concentration. It is then chemically processed to form yellowcake U3O8. Then, uranium hexafluoride gas UF6 is produced by fluorination of U3O8. As a gas, it undergoes enrichment to increase the U235 content from 0.7 to about 3.5. It is then turned into a hard ceramic oxide UO2 for assembly as reactor fuel elements.

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