Fast breeder reactor

A fast breeder reactor is a nuclear power reactor in whose design tradeoffs have been made not to produce the ideal heat for power generation, but to produce reasonable heat but also a substantial amount of high-energy neutrons that will make ("breed") potential nuclear fuel of an appropriate plutonium isotope. Economically, it seems attractive when a reactor can produce 30 percent more fuel than it burns. The reactor product is not immediately usable as fuel, but requires complex and hazardous reprocessing.

There has been hesitancy to use this design, over concerns on weapons-grade plutonium becoming too widely available. Only two, neither of which is operational, has been built in the U.S.