A boosted fission weapon is a type of nuclear weapon that makes use of a small amount of fusion fuel to increase the rate, and thus yield, of a nuclear fission reaction. The fast neutrons released by the fusion reactions add to the fast neutrons released by the fission reactions, allowing for more neutron-induced fission reactions to take place. The rate of fission is thereby greatly increased such that much more of the fissile material undergoes fission before the core explosively disassembles. The fuel is commonly a 50-50 deuterium-tritium gas mixture. The fusion process itself adds only a small amount of energy to the process, perhaps 1%.