In order to enrich uranium in gas centrifuges, it must be converted into its gaseous form – uranium hexafluoride. The enriched fraction is used to produce uranium fuel. The content of the fissile isotope (uranium-235) in the depleted uranium hexafluoride is only 0.1% and the major part of it is uranium-238. Depleted hexafluoride is stored on the plant’s site in special containers. It can be processed to extract pure fluoride (valuable raw material for the chemical industry) and depleted uranium.
This is an example of how abstract the notion “radioactive element” is. Formally, uranium is a radioactive element: it has no stable isotopes at all. At the same time, depleted uranium is a unique material with a very high density (65% heavier than lead). It can be used to manufacture flywheels and balances, as a material for biological protection, containers for radioactive waste, or used in industrial radiography.