Characterization and qualification of neutron radiation effects-Summary of Japan-USA Joint Projects for 40 years

The Joint Projects under the Japan-USA Fusion Cooperation Program started in 1981 and has continued for more than 40 years. In the Joint Projects, although a wide range of fusion materials and engineering issues were covered, neutron radiation effects on fusion reactor materials have always been the major research emphases, and the neutron irradiation facilities in the US were jointly used by Japanese and US researchers. Japanese test facilities including neutron and charged particle irradiation facilities were complementarily used. The initial focus of the Joint Projects was on fundamental fusion neutron radiation effects and irra-diation correlation. Systematic comparison of fission and fusion radiation effects in com parable damage levels and the effects of transmutation-induced helium were investigated. The collaboration was then focused on the effect of dynamic irradiation effects in variable conditions. In addition to the relatively fundamental studies, the Joint Projects contributed largely to development of candidate materials such as RAFM steels, vanadium alloys, SiC/SiC composites, and tungsten alloys, through a mechanism-oriented approach. The Joint Projects also covered issues specific to materials application to fusion blankets and plasma-facing components, including neutron radiation effects such as tritium retention and permeation of neutron-irradiated plasma-facing materials. Various irradiation technologies were developed and ap-plied to the irradiation experiments, including those for in-situ testing. Considering that high energy neutron sources, such as A-FNS and IFMIF-DONES, now have high via-bility, the research supporting the neutron source programs is essential. The knowledge obtained through the Joint Projects is valuable and should be advanced for this purpose. To this end, it is of urgent ne-cessity to launch an international scientific program accumulating knowledge of fusion neutron radiation effects, including their fundamental aspects. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The Joint Projects under the Japan-USA Fusion Cooperation Program have been conducting research on neutron radiation effects on fusion reactor materials for over 40 years. The projects have focused on fundamental radiation effects, correlation of irradiation, and the development of candidate materials, contributing significantly to the advancement of fusion technology.