aneutronic fusion is fusion using fuels such as proton–boron-11 that release little or none of their energy as neutrons, at the cost of far higher required temperatures than deuterium-tritium fusion.
The appeal of aneutronic fuels is everything the neutron complicates. In the 📝D-T reaction, 80 percent of the energy leaves as a 14.1 MeV neutron, which damages structural materials, activates them, and obliges the plant to breed 📝tritium. Proton–boron-11 fusion instead yields three charged 📝alpha particles and no neutron at all, while deuterium–helium-3 produces a proton and an alpha particle, with neutrons arising only from side reactions. Because the products are charged, their energy could in principle be converted to electricity directly, without a steam cycle.
The price is steep. Aneutronic reactions have far smaller fusion cross-sections than D-T and require ion temperatures roughly an order of magnitude higher — billions of degrees for proton–boron-11 — while radiation losses climb with the fuels' higher nuclear charge. Whether a proton–boron-11 plasma can produce more fusion power than it radiates away remains an open physics question. That is why aneutronic fusion is pursued by a minority of fusion companies and research programs, and why first-generation power plants are designed around the neutron-producing but far more attainable D-T fuel cycle.