Graphites and C/C Composites for Generation IV Nuclear Reactors

Carbon-based materials are closely linked to the development of nuclear technologies. Enrico Fermi used them as neutron moderators in the first fission reaction he carried out at the University of Chicago in 1942. Since then, over 250,000 tonnes of graphite (including 23,000 tonnes in France) have been used to control fission in 125 nuclear reactors worldwide. Graphite has many qualities that make it an excellent candidate for nuclear applications: it is a good neutron moderator; it has interesting mechanical properties at high temperatures; and, provided it is sufficiently pure, it activates relatively little under irradiation. What's more, it has excellent machinability and relatively low production costs.

The invention of C/C composites, materials with enhanced performance thanks to carbon fibers reinforcing the carbon matrix, also opened up new fields of application for the nuclear industry. These materials were developed in the 1970s for rocket engine nozzles and atmospheric re-entry heat shields for missiles, then, in the 1980s, for aircraft brakes and parts for high-temperature furnaces. Studies and development for the nuclear industry also began in the 1980s, for high-temperature reactors (HTRs), and, from the 1990s onwards, for fusion. Since the early 2000s, they and SiC/SiC composites have also been identified as candidates for 4th generation reactors (GEN-IV), but optimizing them to withstand extreme conditions of temperature, irradiation and mechanical stress represents a real scientific and technological challenge.

This article presents the potential applications of graphite and C/C for 4th generation reactors, their specific manufacturing processes, their characteristics and properties, as well as their often complex behavior under irradiation.