Why materials science is the hardest unsolved problem in fusion engineering — no material on Earth has been tested under the extreme neutron, heat, and plasma conditions of a fusion power plant.
A fusion power plant’s structural materials face a combination of extreme conditions that no material has ever been tested against simultaneously: (1) 14.1 MeV neutrons causing atomic displacement damage at 20–30 dpa/year; (2) volumetric nuclear heating; (3) helium and hydrogen gas production inside the metal lattice; (4) surface heat fluxes up to 20 MW/m² on the divertor; (5) temperatures of 300–1000°C; and (6) corrosion from liquid metals or coolants.[1]
Reduced-activation ferritic-martensitic (RAFM) steels (EUROFER-97): The near-term choice, limited to ~550°C. Oxide-dispersion-strengthened (ODS) steels: Higher-temperature variants, harder to fabricate. Tungsten alloys: For the divertor, but brittle under irradiation. Silicon carbide composites (SiC/SiC): Promise operation above 1000°C but joining and hermeticity are unsolved. Vanadium alloys: Low activation, good at high temperature, but oxidise in air.[2]
The international IFMIF-DONES facility (under construction in Granada, Spain) will use a deuterium-lithium stripping reaction to produce a high-flux 14 MeV neutron beam for materials testing. It is expected to begin operations in the early 2030s — the first facility capable of qualifying materials for fusion service.[3]