Fusion reactors: the challenge of materials

Fusion reactors like tokamaks will impose to the materials facing the thermonuclear plasma, very high flux of particles mainly fast neutrons, very high temperatures and very high heat fluxes. Today these materials do not exist yet and will have to be designed purposefully. The lines of research are: -) the nano-structuring of materials (it means the introduction of a high density (1023/m3) of nano-metric size precipitates so that the interfaces with the matrix will be a trap for eliminate punctual defects), -) the modeling of irradiation damages and its experimental validation with charged particles, and -) the use of tungsten for the divertor. The new materials will have to be validated on the IFMIF facility (International Fusion Materials Irradiation Facility). The neutron source of the IFMIF project is based on 2 nuclear reactions: 7Li + d → 7Be + 2n and 6Li + d → 7Be + n in which the incident deuterons have an energy of 40 MeV and impinge on a natural lithium liquid target. The neutron spectrum will have a broad peak around 14 MeV which is adequate for the simulation of atom displacements and interstitial helium generation typical of fusion reactors. (A.C.)