Fast breeder reactor development is concentrated on the liquid metal-cooled fast breeder reactor (LMFBR). Almost a dozen countries have major development and industrialization programmes related to the commercialization of LMFBRs. Development of LMFBRs has been underway for more than 35 years. During this period 19 LMFBRs have been constructed and operated. Presently, ten LMFBRs are operating, five are under construction, and five are in an advanced stage of planning. Present nuclear power technology and known uranium resources can serve as energy sources for about 50 years. However, with breeders, nuclear fission offers an almost inexhaustable source of energy, as they can utilize 60 to 70 times more of the energy contained in a unit mass of uranium. In addition, breeders will expand the volume of available uranium resources because of their ability to exploit economically lower concentration ores