Materials and the First Wall

Material choices center on handling steady heat and radiation with low activation, since the burner's neutron load is small but not zero.

A different materials problem than D-T

A D-T fusion plant's materials challenge is dominated by intense 14 MeV neutron damage. The burner's 5.44% neutron fraction changes the emphasis: the dominant loads on plasma-facing materials are steady radiation and particle flux, with neutron damage secondary. This shifts the selection criteria and widens the field of viable materials.

Selection criteria

• High-temperature strength for steady heat flux on the first wall
• Low sputtering, to keep impurities out of the radiation-sensitive plasma
• Low activation, for hands-on maintenance and a thin waste inventory
• Compatibility with the coolant and with permeation control for tritium

Shared work with the breeder

Kronos's materials effort spans both machines. The breeder's high-field magnet and structural materials work, and its REBCO conductor characterization, carry over to the burner, whose magnets use the same conductor. The direct-converter collectors add their own materials problem — high-voltage, high-flux surfaces that must resist sputtering and shed secondary electrons.

Material selection for the burner is part of the design study, drawing on the fusion materials literature and Kronos's own analysis rather than on built-hardware experience. The reduced neutron load is a genuine simplification, but low activation and impurity control remain first-order requirements, and the test unit is where materials behavior is first observed in the real environment.

Material behavior under long, steady exposure — rather than under a single intense neutron pulse — is the regime the burner cares about, and it is precisely this steady-state materials performance that the test unit is positioned to measure over extended operation.