Materials Qualification for 14 MeV Neutrons
Fusion's 14 MeV neutrons damage materials in ways fission data cannot fully predict; qualification is an open program for the whole field.
A spectrum without a database
D-T fusion produces 14 MeV neutrons — far more energetic than fission neutrons. They displace atoms and, importantly, produce helium and hydrogen inside materials through transmutation, which drives swelling and embrittlement in ways fission-reactor data does not fully capture. Qualifying materials to this spectrum is an open problem across fusion, not unique to the breeder.
Why existing data is not enough
No operating facility yet produces a full-fluence 14 MeV spectrum, so material lifetimes at high dose are extrapolated from fission irradiation, ion beams, and modeling. Each surrogate misses part of the picture — fission lacks the high helium generation, ion beams lack depth and volume. The breeder's center-post, first wall, and structure all depend on closing this gap.
- 14 MeV neutrons produce more helium and hydrogen per dpa.
- Transmutation gases drive swelling and embrittlement.
- No facility reproduces the full spectrum at fluence today.
- Lifetimes are extrapolated and must be verified as data arrive.
Honest posture
The breeder treats 14 MeV qualification as open, monitored work. Component lifetimes such as the ~0.01 fpy center-post note are working figures to be confirmed against real damage data, not settled numbers. Stating this plainly is part of the machine's design-and-simulation status.
Surrogates and modeling together
Because no single facility reproduces the full spectrum at fluence, qualification combines fission irradiation, ion beams, spallation sources, and physics-based modeling, each covering part of the gap. The breeder cross-checks these surrogates against one another and against operating data as it accumulates, treating lifetime predictions as bounded estimates to be tightened, not final numbers.
This page documents a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. Figures are computed, reproducible targets, not measurements.