Korea has put in a huge effort to develop the future nuclear systems such as a sodium-cooled fast reactor (SFR), a very high temperature reactor (VHTR) and fusion reactor. As the realization of such nuclear systems relies heavily on performance of materials, Korea has made steady and persistent effort to develop structural materials that can withstand the extremely harsh operating conditions. The present paper summarizes the current status of the Korean R&D activities on advanced nuclear materials including oxide dispersion strengthened (ODS) steels, Ni- base alloys and their ODS variations, reduced-activation ferritic-martensitic (RAFM) steels, and SiC composites

A chromium diffusion coating was applied on an oxide dispersion strengthened ferritic-martensitic (ODS-FM) steel to improve oxidation resistance at high temperature. By carrying out physical vapor deposition followed by inter-diffusion heat treatment, a thin Cr-rich carbide layer was produced on the ODS-FM steel. Both the as-received and surface-modified specimens were oxidation-tested at 650 °C in air and steam environments for 500 h. The surface-modified specimens showed improved oxidation resistance in both environments. In an air environment, both conditions exhibited a thin and continuous chromia layer, but the formation of Cr₂O₃ and (Mn, Cr)₃O₄ nodules resulted in greater weight gain for the as-received specimen. In a steam environment, weight gain increased for both the as-received and surface-modified specimen. Especially, the as-received specimen showed much greater weight gain with the formation of a thick oxide layer consisted of outer Fe-rich oxide and inner (Fe, Cr, Mn) oxide layers. On the other hand, a thin and continuous chromia layer was formed for the surface-modified specimen, which resulted in much less weight gain in a steam environment.