A liquid metal fast breeder (LMFBR) is a type of nuclear reactor which is capable of producing more so-called fissile material than it takes in. A LMFBR has exceptional fuel economy when compared with a light water reactor. A LMFBR uses liquid metal to regulate heat in heat transfer systems instead of water due to its high conductivity and overall better ability to distribute heat effectively.
A breeder is named such due to it’s ability to breed fuel or produce more usable fuel. A breeder reactor uses a fissile material as fuel, which is a material that is capable of sustaining a nuclear fission chain reaction. Fission means dividing or splitting especially splitting the atom. A breeder reactor produces more fuel than it takes in and is self-perpetuating.