An application of the reduced-activation ferritic-martensitic steels is limited in relatively lower temperature due to their softening or loss of creep strength. In order to extend a design window toward higher temperature in these steels, technology development of introducing the oxide dispersion strengthened (ODS) type is conducting in Japan. The 8Cr-F82H based ODS steels were fabricated and their tensile & charpy impact properties were evaluated. The 9Cr-JLF-1 based ODS steels were also fabricated and evaluated. Both Y_2O_3 type ODS steels are under irradiation in JMTR. The ODS-type steels were basically developed as the most promising FBR fuel cladding in JNC, expecting the excellent radiation resistant and superior strength at an elevated temperature of around 700°C. Using 9Cr and 12Cr ODS steels, manufacturing cladding tubes by the cold pilger mill rolling was extensively conducted by controling the grain structure morphology. The improved high temperature mechanical properties of the manufactured tubes at 700°C were characterized focussing on the reduced size of Y_2O_3 particles and shortening the inter-particles spacing.
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