Mechanical properties, structural changes and hydrogen interactions with stainless steel 12Cr18Ni10Ti subjected to accelerated radiogenic He-3 buildup by means of "tritium trick" technique were studied. After saturation with tritium up to equilibrium concentration at a pressure 50 MPa and T=773 K the samples were rapidly cooled to room temperature and aged at this temperature up to the buildup of a predetermined He-3 concentration. Kinetics of helium thermal release, hydrogen transport, trapping and accumulation in steel containing various concentration of He-3, synergistic influence of He-3 and hydrogen on mechanical properties of steel containing up to 500 appm He-3 and structural changes at various He-3 concentrations are discussed.