[en] In the SSC RF-IPPE the researches are carried out directed towards the uranium dioxide fuel pellets modification with the purpose of improvement of their performance parameters (increase of thermal conductivity, growth of grain for decrease gas release, decrease of interaction with coolant). The following technological methods of manufacturing of modified pellets UO₂ were used: 1) The water method including precipitation of Ammonium Polyuranate (APU) with manufacturing of simultaneously coarse and super dispersed particles, and also coprecipitation APU with additives (Cr, Ti, etc.), with the after calcination of powders, reduction to UO₂ pressing and sintering of pellets; 2) A method including addition of chemical reagent containing ammonia to the powder UO₂ manufactured under the dry or water technology; mechanical mixture; pressing and sintering of pellets. Application of the specified up methods makes manufacturing the UO₂ fuel pellets having the properties differing from pellets manufactured by industrial technology. Conclusions: 1) Properties of powders and the pellets manufactured by different technologies considerably differ; 2) Precipitate manufactured by water industrial technology, consists of phase NH₃·3UO₃·5H₂O whereas the precipitate manufactured by nanotechnology contains in addition phase NH₃·2UO₃·3H₂O; 3) Powders of U₃O₈ manufactured by water nanotechnology have particles size 300-500 nm and ultra dispersive particles size ∼70-75 nm; 4) Powder UO₂ obtained by water nanotechnology differs by greater activity because all phase changes under oxidation result at lower temperatures; 5) Basic differences of properties of modified UO₂ pellets was established: decreasing of defects inside and on grains boundaries, minor porosity (pore size 0,05-0,5 μm), presence of pore of spherical form, presence of additional chemical bond U-U (presence of metal clusters), polyvalence of U; 6) Methods including addition of Cr and Ti under precipitation of APU and also ammonium additives in UO₂ powder result manufacturing pellets with grain size up 20-40 μm; 7) Autoclave tests showed, that UO_2,25 thin protective film is formed under interaction with water on surface of modified pellets and it protects the pellet from destruction. Modified pellets will allow elevate safety of a reactor in case of Fuel Element depressurization conditions, i.e. at contact to water; 8) The reliability of new fuel will be given after reactor tests