The structural state of steel 10Kh18N10T after long-term radioactive irradiation at about 480°C is studied. The microstructure of the steel is analyzed by the EBSD technique using a scanning microscope. The texture of the specimens is investigated by plotting direct pole figures. It is shown that a directed martensitic transformation develops in the surface layer of the steel under the action of internal stresses caused by radiation swelling. Fine particles of secondary austenite precipitate in the formed martensite and obey orientation relations not coinciding with the relations acting under the primary shear γ - α transformation in a part of the bcc crystallites.