Recent Research and Development of Reduced Activation Ferrous Materials in Japan

Abstract

The outline of research and development of reduced activation ferrous materials, today in Japan, is reviewed. Reduced activation ferrous materials are considered to be utilized for the first wall materials of fusion reactor. The concept of reduced activation materials is closely related to the waste management and reactor safety. The decay behavior of induced radioactivity shows that the substitution of Mn for Ni and that of W for Mo in ferrous materials are very effective to achieve a reduced level of long-term radioactivity. The efforts are being devoted to the development of ferritic 9Cr-W steels, austenitic Mn-Cr steels and Mn-Cr-W steels as candidate alloys, instead of 9Cr-Mo steels and modified type 316 stainless steels. Some results are presented to the toughness before and after neutron irradiation and creep rupture strength of 9Cr-W steels, and on the characteristics of sigma phase formation, high-temperature strength, and void swelling of austenitic Mn-Cr steels and Mn-Cr-W steels. Preferable chemical compositions for reduced activation ferrous materials are suggested.