Blanket Neutronics

The blanket must slow, multiply, and capture neutrons to breed tritium while surviving the flux; its neutronics set the achievable breeding ratio.

The layer that does the work

The breeding blanket surrounds the plasma and is where the foundry's chemistry happens. Its neutronics must accomplish several things at once: moderate a portion of the fast neutrons so that ⁶Li capture is efficient, multiply neutrons where the ⁷Li and multiplier reactions allow, capture the bred tritium for extraction, and absorb the neutron energy as recoverable heat — all while withstanding the damage the flux inflicts.

These goals compete. Moderating material and structure absorb neutrons that could have bred tritium; multipliers add neutrons but also parasitic capture; more structure means more strength but lower breeding. The blanket design is an optimization among breeding, heat handling, and mechanical survival, and its outcome is what fixes the net TBR.

The honest coupling to the TBR question

Because the blanket sets net breeding, every open question about TBR 1.8 is ultimately a blanket-neutronics question. Realistic coverage, the fraction of the plasma the blanket can surround, the penetrations it must accommodate, and the parasitic absorption of its own structure determine whether the ambitious lever setting is reachable. This is quantified by simulation and remains to be confirmed against a built blanket.

• Moderates, multiplies, and captures neutrons; recovers heat
• Competing goals: breeding vs structure vs heat vs survival
• Blanket neutronics fix net TBR — the crux of the 1.8 question

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.