Conversion - hdbk1113cn10126

DOE-HDBK-1113-98

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

extraction.

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.

Conversion

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."