Table of Contents
Conversion
In the Uranium Conversion stage, yellowcake (U3O8) powder is dissolved in nitric acid (HNO3) and converted to uranium hexafluoride (UF6) or, previously, uranium metal (U). UF6 is commonly known as “hex”.
Why is conversion necessary?
Advantages of uranium hexafluoride (UF6), or “hex”, include…
Hex is a crystalline solid at room temperature – ideal for transportation.
Hex sublimes to a gas at a relatively low temperature, 56.5 °C – ideal for enrichment processes.
At high pressures, hex has a liquid phase – ideal for being pumped around chemical processes.
Fluorine is mono-isotopic – ideal for enrichment processes.
How is conversion carried out?
The yellowcake (U3O8) powder is dissolved in nitric acid (HNO3).
Hydrogen is used to reduce the aqueous solution of U3O8 (and UO3) to uranium dioxide (UO2):
U3O8 + 2 H2 → 3 UO2 + 2 H2O
Uranium dioxide (UO2) is reacted with hydrofluoric acid (HF) to form uranium tetrafluoride (UF4):
UO2 + 4 HF → UF4 + 2 H2O
Uranium tetrafluoride (UF4) is fed into a fluidised bed with fluorine gas (F2) to form hex (UF6):
UF4 + F2 → UF6
