The Open TBR 1.8 Reconciliation

Whether the target TBR of 1.8 survives realistic blanket coverage and losses is an open reconciliation — the breeder's central physics question, stated plainly.

The gap to reconcile

A tritium breeding ratio of 1.8 is the ambitious end of Hyperion's lever and the basis for the ~4 kg/yr tritium class output. The open question is whether 1.8 is achievable once realistic blanket coverage, penetrations, structural materials, and losses are accounted for. Idealized neutronics can approach high TBR values; a real machine with ports, gaps, and a center post that cannot host a full blanket generally achieves less.

This is the breeder's central reconciliation, and it is stated openly. The concern is specifically the difference between a local breeding figure computed for an idealized blanket segment and the net breeding of the whole machine after coverage limits and losses. The two can differ substantially, and closing that gap is unfinished work.

How it is being handled

Rather than assert 1.8, the design carries the full lever (1.1 / 1.5 / 1.8) so that conclusions are visible at each setting, and flags 1.8 as requiring reconciliation before it can be treated as achieved. Tritium self-sufficiency is not yet proven at any setting. The FOAK build and its measured breeding are what will ultimately settle the number.

• 1.8 underpins the ~4 kg/yr tritium class figure
• Realistic coverage, penetrations, and losses may reduce achievable TBR
• Local-vs-net breeding is the specific gap; self-sufficiency is unproven

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.