Abstract: A dispersion strenghened ferritic steel having excellent ductility and toughness which has been heat treated to produce a matrix having a tempered martensitic structure composed of 0.05 to 0.25% by weight of carbon, 0.1% by weight or less of silicon , 0.1% by weight or less of manganese, 8 to 12% by weight of chromium, 0.1 to 4.0% by weight in total of molybdenum and tungsten, and 0.02% by weight or less of oxygen (exclusive of oxide particles) with the balance being iron and inevitable impurities and, homogeneously dispersed in the matrix, composite oxide particles comprising Y.sub.2 O.sub.3 and TiO.sub.2 in an amount of 0.1 to 1.0% by weight in total of Y.sub.2 O.sub.3 and TiO.sub.2 and a TiO.sub.2 to Y.sub.2 O.sub.3 molar ratio of 0.5 to 2.0.

Abstract: A dispersion strengthened ferritic steel cladding tube for use in a nuclear reactor and having a double-layer structure is provided. The cladding tube comprises a tube body made of a dispersion strengthened ferritic steel having a ceramic dispersed therein and containing 8 to 13% by weight of chromium. The inner surface of the tube body is lined with a ferritic steel containing 18 to 30% by weight of chromium. The cladding tube has not only excellent compatibility with a mixed oxide fuel but also excellent high temperature strength and swelling resistance.A method of producing the cladding tube using powder metallurgy is also provided.