Source: Appendix A of the PEIS (DOE/EIS-0269)
Uranyl fluoride (UO2F2) is an intermediate in the conversion of UF6 to an uranium oxide or metal form and is a direct product of the reaction of UO2F2 with moisture in the air. It is very soluble in water. Uranyl fluoride also is hygroscopic and changes in color from brilliant orange to yellow after reacting with water. Uranyl fluoride is reported to be stable in air to 570°F (300°C), above which slow decomposition to U3O8 occurs. When heated to decomposition, UO2F2 emits toxic fluoride fumes.
Uranyl fluoride (UO2F2) is a yellow hygroscopic solid that is very soluble in water. In accidental releases of UF6, UO2F2, as a solid particulate compound, may deposit on the ground over a large area.