Technically, fast neutron reactors provide an elegant solution to the recycling question because all plutonium isotopes can be fissioned by fast neutrons. This allows the isotopic quality of the plutonium to be maintained or improved. Most fast reactors use plutonium as their driver fuel, with easily enough neutrons being produced to sustain the chain reaction. Fission of plutonium-239, for example, produces 25% more neutrons than uranium-235. This means that there are enough neutrons (after losses) not only to maintain the chain reaction but also to convert U-238 into more Pu-239 continuously. Such breeding is also possible in thermal reactors, of course, but not so easily or effectively.

Fast reactor technology is important in long-term considerations of world energy sustainability and they have also been suggested as vehicles for burning ex-military plutonium, about which there is international concern. In economic terms, however, much depends on the value of the plutonium fuel, which is bred and used and this, in turn, relates to the cost of fresh uranium.