Low-Neutron and Waste: A Glossary
Plain definitions for the terms used across this section, from activation and clearance to dpa and transuranics.
This glossary defines the terms used throughout the low-neutron and waste section, so the rest of the pages can be read without hunting for meanings. Definitions are kept plain and specific to the fusion context.
Neutron and activation terms
- Low-neutron: a fuel cycle emitting a small neutron fraction — here 5.44% for the D–³He burner — as opposed to aneutronic (zero).
- Aneutronic: emitting no neutrons; the burner is not aneutronic.
- Activation: the process by which neutrons make stable atoms radioactive.
- Transmutation: the change of one element into another by nuclear reaction.
- dpa (displacements per atom): a measure of accumulated neutron damage in a material.
- Fluence: neutrons per unit area integrated over time.
Waste and disposal terms
- LLW / ILW / HLW: low-, intermediate-, and high-level waste; fusion produces the first two and none of the third.
- Clearance: release of material below regulatory thresholds for recycling or reuse.
- Actinides / transuranics: long-lived heavy elements (e.g. plutonium) bred in fission fuel; absent in fusion.
- Radiotoxicity: the biological hazard of a material if taken into the body.
- Detritiation: removing tritium from a material to recover it and lower the waste class.
- Reduced-activation material: an alloy or composite formulated to activate to mostly short-lived nuclides.
Used consistently, this vocabulary keeps the section's claims precise: low-neutron rather than aneutronic, activated structure rather than spent fuel, clearance rather than permanent waste. Precise words are part of the candor — they let a reader hold the machines to exactly what the physics supports, no more and no less.
These definitions apply across the section and are consistent with the frozen design points of both Kronos machines, which remain design-and-simulation studies. Where a term implies a number, the number is the canonical one used everywhere on this site.