Scheme of tritium breeding.

Method of tritium production in a fusion reactor by neutron capture in lithium. D-T fusion requires two isotopes of hydrogen, deuterium and tritium, as fuel. While deuterium is abundant on Earth, tritium is very rare. However, it can be produced directly in the reactor in tritium breeders inside blanket panels. The fusion reaction produces neutrons that collide with lead or beryllium atoms in the tritium breeder. These atoms act as neutron multipliers, producing from a single neutron a shower of neutrons that collide with lithium6 nuclei. The resulting 3 protons and 4 neutrons are then rearranged into one atom of helium (2 protons and 2 neutrons) and one atom of tritium (1 proton and 2 neutrons) while energy is released. Tritium breeders can be solid panels containing pebbles of beryllium and lithium in their compartments, or a liquid mixture of lithium and lead can flow through them. Solid breeders must be removed from the reactor for tritium extraction. Conversely, tritium may be extracted continuously from the liquid mixture.