TBR as a Design Lever

Hyperion treats the tritium breeding ratio as a lever set at 1.1, 1.5, or 1.8 rather than a single figure, because the achievable value is not yet settled.

Why a lever, not a number

Most fusion literature quotes a single required tritium breeding ratio. Hyperion instead carries three explicit lever settings — 1.1, 1.5, and 1.8 — and evaluates the machine at each. This is deliberate honesty: the achievable TBR depends on blanket coverage, choice of multiplier, lithium enrichment, and how much of the plasma the blanket can actually surround, none of which is fully fixed at the design-and-simulation stage.

The three settings bracket the outcome. A TBR near 1.1 is barely self-sufficient and leaves little margin for losses; 1.5 provides comfortable margin and surplus for inventory build-up; 1.8 is an ambitious target that would allow rapid tritium accumulation and export, and is the setting behind the ~4 kg/yr tritium class figure.

What the lever exposes

Carrying the lever makes the sensitivity visible: the product yields, the time to become tritium self-sufficient, and the fuel-cycle margin all move with TBR. It also frames the central open question — whether the ambitious 1.8 setting survives realistic blanket coverage and losses. Rather than assume it, the design keeps all three on the table and flags 1.8 as the setting that needs reconciliation.

• 1.1 — marginal self-sufficiency, little loss margin
• 1.5 — comfortable margin, inventory build-up
• 1.8 — ambitious target behind ~4 kg/yr; needs reconciliation

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.