Why tungsten is the leading material for fusion reactor divertors — with the highest melting point of any element, low sputtering, and low tritium retention, but challenged by neutron-induced embrittlement.
Tungsten (W) is the primary candidate material for divertor plasma-facing components in fusion reactors due to its extraordinary properties: the highest melting point of any element (3,422°C), very low sputtering yield under hydrogen isotope bombardment, low tritium retention, and high thermal conductivity. These properties make it uniquely suited to withstand the extreme heat fluxes (10–20 MW/m²) at the divertor strike points.[1]
Neutron embrittlement: Under fusion neutron irradiation, tungsten’s ductile-to-brittle transition temperature (DBTT) rises dramatically, potentially above operating temperature, making it prone to cracking. Recrystallisation: At temperatures above ~1,200°C (achievable during transients), tungsten recrystallises and loses its engineered mechanical properties. Melting: During disruptions or giant ELMs, surface temperatures can briefly exceed tungsten’s melting point.[2]
Research on tungsten alloys (W-Re, W-TiC, W-Y2O3), tungsten fibre-reinforced tungsten composites (Wf/W), and self-passivating tungsten alloys (W-Cr-Y) aims to improve ductility and oxidation resistance beyond what pure tungsten can offer.[3]