First-Wall Neutron Loading

The first wall takes the full neutron flux; its loading, in MW per square meter, sets damage rate and replacement cadence.

The first wall is the surface facing the plasma. It intercepts the neutron flux before any blanket or shield, so it experiences the highest loading and the fastest damage. First-wall neutron loading is expressed as the neutron power crossing each square meter of surface.

Breeder loading

In Hyperion the compact spherical-tokamak geometry concentrates an 88.7 MW fusion output, four-fifths of it neutrons, onto a modest wall area. That produces a demanding neutron load that drives displacement damage and transmutation, and it is the reason the first wall and blanket are engineered as periodically replaced modules rather than lifetime components.

Burner loading

The burner's wall sees only the 5.44% neutron channel, so even in a compact tandem-mirror the neutron loading is a small fraction of the breeder's. The dominant wall challenge in the burner is heat and charged-particle flux, not neutron damage — a direct consequence of the low-neutron fuel cycle.

Loading is not uniform across the wall: geometry concentrates flux at some locations and shadows others, so replacement is planned around the hottest zones. Mapping the loading distribution in simulation lets the design place the most robust, most easily recycled materials where the fluence is highest, tightening the waste outcome region by region.

Managing first-wall loading is the front line of the waste strategy: the less a wall is loaded, the slower it damages, the less it transmutes, and the more favorable its eventual waste class. All values are design-and-simulation inputs for machines whose first-of-a-kind operation is still ahead.