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Fast reactors

A nuclear reactor capable of producing its own fuel? It’s not science fiction, but the principle of the breeder reactor, also called fast-neutron reactor. Like other reactors, it produces energy in a plutonium core, but some of the neutrons emitted in the fission reactions are used to bombard the uranium-238 (the most abundant uranium isotope) present in the fuel, transmuting it into uranium-239, then neptunium and ultimately into plutonium.
Several breeder reactor concepts were selected by the Generation IV International Forum, but the most advanced is indisputably the sodium-cooled fast reactor. As the name suggests, it uses sodium as a coolant to transfer heat from the reactor. The same principle was used in the two CEA and EDF PHENIX and SUPERPHENIX breeder reactors, which were decommissioned in 2009 and 1998 respectively. The Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID), an experimental breeder reactor that could go online in 2020, is also sodium-cooled.
Does this mean that sodium-cooled fast reactors are the future of nuclear power? Some critics point to their daunting complexity, in particular the difficulty of using sodium, a liquid so volatile it ignites upon contact with water and air. There is no guarantee that this type of reactor could be made safer than an EPR, but it could nonetheless become viable should uranium become scarcer and therefore more expensive. For this reason, many countries are taking an interest in sodium technology. Another alternative would be the development of gas- or lead-cooled fast reactors, although these technologies are much less advanced.