[en] Full text: A life limiting factor of the austenitic steels in fuel assemblies is a functional limit due to swelling induced distortions of a fuel pin bundle in a wrapper tube. Austenitic steels are the very complex multi-components systems. Possible improvement of exploitation characteristics of ASS can be realized in increasing of stability of all structural components of ASS (defect structure elements, solid solution and precipitates), which can be achieved by optimal composition and thermo-mechanical treatment The maintenance of desirable swelling is directly coupled with maintaining a more stable microstructure during irradiation. Analysis of all structural components evolution in irradiated austenitic steels is carried out:-of dislocation structure which stability is determined by the stacking fault energy and by segregation processes possibility on the dislocation components, of solid solution state determined by point defects diffusion characteristic and by the concentration of elements radiation induced segregation of which changes the solid solution homogeneity, - of second phase precipitates the stability of which determines the radiation swelling resistance due to the increase of point defects strength and their recombination on the interface matrix-precipitate. It is shown that precipitates in irradiated austenitic stainless can be separated on two families: - Precipitates which are responsible for swelling suppression due to enhancing point defect recombination at particles-matrix inter MC (mainly TiC, NbC,VC), Fe₂P or Ni₃Ti (in a few cases). - Precipitates which serve as result of solid solution decay (especially due to removing from solution of Ni and Si as result radiation-induced segregation) and sign as loss of radiation stability at stages of structure evolution. It appears that this competition can be prolongated by optimization of composition and by the thermal-mechanical treatment. Possible mechanisms of swelling suppression in modern austenitic steels are described