To improve material properties of reduced-activation ferritic steels, mechanical properties and microstructure of the steels with adjusting minor alloying elements, such as N, B, Ta, and Ti were investigated. If it became necessary to reduce N contents in the steels for nuclear consideration, B-addition would have the potential to produce a steel comparable, at least in terms of mechanical properties before irradiation, to the JLF-1 IEA heat. Increasing the Ta contents could induce further grain refinement in the JLF-1 steel, but had no significant effect on the tensile and impact properties.