Engineering Copilot: Fuel-Cycle and Isotope Reasoning

Reasoning over the breeder's tritium and helium-3 balance and the burner's D-3He supply, grounded in the twin's fuel-cycle module.

Closing the isotope loop

The breeder (Hyperion) exists to produce isotopes: a tritium-breeding design targeting the ~4 kg/yr tritium class and ~1.97 kg/yr helium-3, alongside 14 MeV neutrons. The Engineering Copilot reasons over the fuel-cycle inventory — tritium bred, burned, retained, and extracted — using the twin's fuel-cycle and isotope-balance module. It answers questions about inventory margin, self-sufficiency, and extraction scheduling.

The breeding-ratio lever

Tritium breeding ratio (TBR) is treated as a design lever spanning 1.1 / 1.5 / 1.8, not a fixed number. The copilot frames inventory reasoning against the chosen lever and is explicit that TBR is a design choice with an honest local-versus-net distinction. It never asserts self-sufficiency as settled; it cites the twin's balance and flags the open reconciliation.

fuel_balance(t):
  bred    = TBR * burn_rate(neutron_output)       # TBR in {1.1,1.5,1.8}
  losses  = decay + retention + extraction_ineff
  dI/dt   = bred - burned - losses
  report:  inventory margin, doubling context (schedule only),
           He-3 co-product ~1.97 kg/yr class
  flag:    local TBR vs net self-sufficiency (open reconciliation)

Burner fuel reasoning

• D-3He supply logistics reasoning (schedule and inventory, not economics)
• Helium-3 handling and accountancy across both machines
• Neutron-fraction context: 5.44% burner vs D-T breeder neutron budget
• Cross-machine isotope flow (breeder He-3 co-product as burner-relevant context)

All quantities are physical and schedule facts — inventories, rates, kilograms-per-year classes. The copilot is barred from economics: no monetary, value, or market framing enters its reasoning or output. Fuel-cycle conclusions are cited to the twin's isotope-balancing module and the frozen product canon, and any inventory action is a proposal to L4. See the twin fuel-cycle balance and TBR sweeps.