Tungsten and Plasma-Facing Materials
The surfaces facing the plasma must survive extreme heat and particle flux; tungsten is the leading choice, with a bounded, sourceable supply.
The first surfaces facing the plasma endure intense heat flux and particle bombardment. They must resist erosion, tolerate high temperature, and not contaminate the plasma badly. Tungsten is the leading plasma-facing material because of its very high melting point and low erosion rate.
Use and supply
Tungsten is used as armor tiles or coatings on the first wall and divertor-equivalent surfaces. The quantity per plant is bounded — it lines surfaces, it does not fill a volume. Tungsten supply is globally concentrated but the element is not fundamentally scarce for these quantities, and recycling of tungsten components is established practice in industry.
Honest constraints
- Neutron exposure activates and embrittles plasma-facing materials over time, so they are lifed components replaced on schedule.
- Replaced components enter the activated-material stream, handled as a known, decaying inventory.
- The burner's low neutron fraction (5.44%) means less first-wall neutron loading than the D-T breeder's 14 MeV flux.
- Component lifetimes under real flux are a design-and-simulation estimate, not yet plant-demonstrated.
The defensible claim is that plasma-facing materials are a solved-in-principle choice (tungsten) with a bounded, sourceable inventory, while component lifetime under neutron flux remains a genuine open engineering question tied to the activation discussion.
Component lifetime under real neutron and heat flux is the honest open question for plasma-facing materials. Tungsten resists erosion and heat well, but neutron exposure embrittles and activates it over time, so these are lifed components replaced on schedule and routed into the activated-material stream. The burner's low neutron fraction eases this relative to the D-T breeder, but lifetimes remain design-and-simulation estimates rather than plant-demonstrated values.