Radiological Safety Traning for Uranium Facilities
Module 102 - The Nuclear Fuel Cycle
It is estimated that the uranium milling in the United States left approximately
138 million tons of mill tailings covering about 3,000 acres of land.
The yellowcake slurry is then purified by either ion exchange or solvent
Following purification, the yellowcake slurry is dried, forming a concentrated
yellowcake compound that contains 75 - 98 percent uranium. The yellow color
is caused by the addition of leaching chemicals and their eventual removal
during the drying step. The final color can range from yellow to orange to black
depending on the chemicals used and the drying temperature.
The final color is a good indicator of solubility, and thus of biological effects if
uranium in this form is taken into the body. Less soluble uranium compounds
tend both to remain in the body longer and to be darker in color. More soluble
uranium compounds are removed from the body more quickly by normal body
functions, and tend to be lighter in color.
At this stage in the nuclear fuel cycle, the yellowcake is converted into uranium
hexafluoride (UF6) for enrich ment. This is ac complished by:
Conversion of yellowcake to pure uranium trioxide (UO3), called "orange oxide"
or "orange sal t," by solvent ex traction an d follow-up dryin g.
Conversion of UO3 to uranium dioxide UO2.
Conversion of UO2 to uranium tetrafluoride (UF 4) by hydrofluorination (addition
of hydrogen fluoride gas). This product is called "green salt."