Background and Mission
For future fusion power reactors (FPR), the materials surrounding the plasma will be irradiated with the high energy neutrons (n) which are generated in the fusion reaction of Deuterium (D) and Tritium (T) forming Helium (He). The typical fusion neutron energy is 14.1 MeV, which is considerably larger than the energy of neutrons emerging from uranium fission. The physics of the neutron induced materials properties change in fusion applications is therefore different from the situation in the already well researched fission applications. Furthermore, to reach high-efficiency fusion power plants, the materials also have to service at elevated temperatures and heat fluxes.
|Left: inside view of a fusion tokamak (JET). Right: fusion nuclear reaction|
Candidate materials, which can service in the structures of fusion power reactor blankets have already been developed. This material class is called Reduced Activation Ferritic Martensitic (RAFM) steels. These iron based steel alloys contain about 9% of chromium, while the contents of molybdenum, niobium, nickel and boron have been significantly reduced. Due to this composition, long lived radioactive products are avoided, and the usage of such material will therefore not contribute to the buildup of radioactive waste which would have to be disposed in a repository. The service temperatures of those materials can go up to 550°C. Newer developments, such as oxide dispersion strengthened grades (ODS-RAFM), can extend the service temperatures to 650-750°C.
In order to finally qualify and license these materials for the service in fusion applications, appropriate tests under fusion-relevant irradiation conditions must be performed. It is the mission of the projected International Fusion Materials Irradiation Facility – IFMIF to serve as a dedicated research instrument for this purpose. IFMIF is therefore a necessary step on the way to use fusion power for our energy supply.