[en] A phase diagram field of the U-O system, adjacent to UO₂ is considered. The methods of uranium dioxide production are briefly outlined. The technology of tablets, granules and microspheres from uranium dioxide production is fundamentally described. Considered are physical properties (thermodynamic properties, vapor pressure, evaporation rate, melting temperature viscosity, thermal conductivity, electric and mechanical properties) and chemical properties (stability in coolants, interaction with fission product oxides, interaction with structural fuel element materials and others) of UO₂. The effect of neutron irradiation and thermal flux in pile on macro- and microstructural changes in fuel elements of UO₂, on the volume increase (swelling) of oxide fuel and extraction of gaseous fission products is described