Neutron Wall Loading

Neutron wall loading is the 14 MeV neutron power per unit first-wall area; it drives breeding, but also damage and heating, and is high in a compact machine.

Neutrons per square metre

Neutron wall loading is the fusion neutron power crossing each square metre of the first wall. It is the quantity that determines both how fast tritium can be bred and how fast the surrounding materials are damaged. A compact machine concentrates a given fusion power onto a smaller wall area, so its wall loading is high — an advantage for throughput and a stress for materials.

For Hyperion this cuts both ways. High wall loading means efficient use of the plasma for breeding and activation, which suits a foundry. It also means the first wall, blanket, and especially the thinly shielded inboard center post accumulate displacement damage and gas production quickly, feeding the center post's limited lifetime.

The design tension

The compactness that makes Hyperion attractive also raises wall loading, and higher wall loading shortens component life. The design accepts high wall loading for its throughput benefit and manages the consequence through material choice, shielding where space allows, and planned replacement of the most exposed parts. Quantifying wall loading and its damage rates is a design-and-simulation exercise central to the materials case.

• Wall loading = neutron power per unit first-wall area
• Sets both breeding throughput and materials damage rate
• High in a compact machine — a throughput gain and a lifetime cost

This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. No hardware net-gain is claimed before FOAK.