We investigate the influence of alloying with rare-earth elements and metals of groups IV-VI on the hydrogen permeability, diffusion coefficient, and hydrogen solubility in EP-838 and Kh12G20V steels proposed as materials for the first wall of a thermonuclear reactor operating on deuterium-tritium plasma. Based on the requirements of ecological safety (hydrogen permeability must be less than 2.4 . 10(-8) mole/(m . sec . Pa-1/2)). we show that the necessary level of hydrogen permeability of EP-838 steel can be reached in the case of alloying with cerium after an additional thermal treatment in hydrogen which initiates the formation of intermetallidic phases of the Fe3Mn type. The value of the hydrogen permeability of Kh12G20V steel corresponds to the level of ecological safety. In this case, alloying with scandium, tungsten, and carbon not only decreases the value of the flow of a diffusing gas fivefold but improves the strength properties due to an increase in the volume fraction of carbide phases.