Neutron Budget and Products
The breeder's 14 MeV neutrons are a budget: some breed tritium, some make helium-3, and some serve materials irradiation.
Neutrons as the product
In a breeder, the fusion neutrons are the product, not a byproduct. Each D-T fusion produces a 14 MeV neutron, and the machine's output at 85.0 MW fusion power is fundamentally a neutron flux that is then allocated to different uses.
How the budget is spent
- Breeding: neutrons captured in the lithium-bearing blanket produce tritium (~4 kg/yr class)
- Coproduction: pathways yield a helium-3 coproduct (~1.97 kg/yr)
- Irradiation services: 14 MeV neutrons for materials testing and isotope production
Why the budget framing matters
A neutron used for one purpose is not available for another. Blanket coverage, penetrations, and multipliers all shift the budget. Framing output as a neutron budget makes the trade-offs explicit: raising breeding ratio, for example, may compete with neutron availability for irradiation services.
Product accounting
The tritium class output near 4 kg/yr is the bankable base product; helium-3 near 1.97 kg/yr is a strategically valuable coproduct; neutron-hours are a service. All three flow from the same 85.0 MW neutron source, which is why gain, not net power, is the requirement.
These are projected outputs for a machine not yet built. The actual budget is measured at the fuel-loop gate, where neutron yield and breeding ratio are reported against pre-registered predictions.