IFMIF: Steps toward realization

The world fusion programme needs within next two decades the results of two large facilities in the race towards commercial fusion power plants based on plasma magnetic confinement. ITER, presently under construction in the South of France will teach us how to control stable deuterium-tritium nuclear fusion reactions. In turn, IFMIF will allow the qualification and characterization of the materials for the first wall of the reactor vessel. The first wall, a combination of layers of different specialized materials that aims to maximize the conversion of neutrons into thermal energy and breed tritium to fuel the fusion reactions, must be capable to withstand structural damage of up to 150 displacements per atom in the metal lattice of purposely designed RAFM (Reduced Activation Ferritic-Martensitic) steels. The 14.1 MeV energy of fusion neutrons makes existing neutron sources (namely fission reactors and spallation facilities) not fully suitable to reproduce experimentally the degradation of mechanical properties of the candidate materials. IFMIF will generate a neutron flux of 1018/m2·s with a broad energy peak at around 14 MeV through (d, Li)n stripping reactions. Two deuteron accelerators with 125 mA, 40 MeV beams and a footprint of 20 cm × 5 cm will impact a liquid Lithium screen flowing at 15 m/s. The neutrons generated will irradiate test modules at different levels of neutron fluxes. Of particular relevance will be the 0.5 l of the High Flux Test Module where miniaturised specimens, presently under qualification, will be tested at various controlled temperatures to reach within a few years the same conditions as the first wall of a commercial reactor vessel. IFMIF, presently in its Engineering Validation and Engineering Design Activities (EVEDA) phase, is overcoming the technical challenges with three main prototyping activities: 1) the world largest liquid Lithium loop, presently under operation in Oarai (Japan); 2) different prototypes of the High Flux Test Module and its cooling loop to independently control the testing temperature in Karlsruhe (Germany) and 3) a deuteron Linac at 125 mA and 9 MeV, which installation starts in March 2013 in Rokkasho (Japan).