Definition of Tritium

Tritium is a relatively rare form of hydrogen isotope with an atomic mass of three (one proton and two neutrons). It is radioactive with a half-life of 12.3 years, decaying into a low energy beta particle with an average energy of 5.7 keV which will not penetrate a sheet of paper. In the natural state, there is only about 10 kg of tritium in the upper atmosphere. But, it can be produced in fission reactors and high-energy accelerators by bombarding lithium or lithium compounds with high energy neutrons. In a larger fusion experimental reactor or power plant, tritium could be continuously generated by using the high energy neutrons from the fusion reaction to transmute the lithium or lithium compounds contained in the surrounding power core. With proper design and choice of materials, the net tritium breeding ratio can exceed one. This means that a fusion plant is capable of generating enough of the tritium part of the fuel mix to be self-sustaining. The other part of the fuel mix, deuterium, is plentiful and easily obtainable from ordinary water.

ITER Test Blanket