Oxide dispersion strengthened(ODS)ferritic steels contain a high number density of nano-sized oxides and fine grains that provide remarkably high tensile strength,good creep resistance or dimensional stability even at elevated temperatures.Moreover,it is well known that ODS steels are often radiation tolerant because radiation damage structures including helium(He)atoms may be trapped by nano-sized oxides and grain boundaries.Therefore,ODS steels have been considered to be one of the candidate structural materials for fusion blankets,where He effects may control lifetime of the blanket structural components.