Reactors of this line do not slow down neutrons. As a result, there is no moderator. For the fuel, either plutonium as fissile material mixed with natural or depleted uranium, or enriched uranium is used.

Ordinarily a fast neutron reactor is composed of a core proper composed of the fissile-fertile mixture of plutonium and uranium in the form of mixed oxides (Mox), and around the core, a cover, composed only of fertile material.

As coolant, a fast reactor uses liquid sodium in spite of the fact that sodium presents the great inconvenience of catching fire in the presence of air and exploding in the presence of water. To try to decrease the danger, a fast reactor has two sodium circuits and a steam circuit. The second sodium circuit, not radioactive unless the primary circuit leaks, transfers heat to the steam circuit.

Excepting critical assemblies and small research reactors, three fast neutron reactors have been constructed in France: Rapsodie, 40 MWth (Cadarache), Phénix, 233 MWe net (Marcoule) and Superphénix, 1200 MWe net (Isère). Rapsodie (undergoing dismantling) and Phénix entered into service in 1967 and 1973 respectively, even before the first big pressurized water reactors. Superphénix is undergoing final shutdown operation.

European Fast Reactor—Under Development

The EFR project was officially launched in 1989 as an initiative in international cooperation, with the participation of a consortium of electric utilities: EFRUG (European Fast Reactor Utilities Group) including EDF of the consortium of construction companies EFR-Associates including Framatome/Division Novatome, and the group of research and development bodies that includes the CEA. The purpose was to create a reactor that could, in the immediate future, help manage wastes and, in the long term, assure a source of energy [EFRA 93]. After ten years of study, the researchers had developed the conception of a nuclear reactor that could equip a commercial power plant (1500 MWe) and meet "the most recent safety standards." However, because Europe is not lacking in energy at present, electricity producers decided, at the end of 1998, to freeze the EFR program. The detailed study will not be begun in the near future [Lefèvre 99]. However, certain studies of future fast neutron reactors are being carried on in different frameworks, such as that of the French Capra project.

Generation IV Reactors--Under Development

France is a member of the Generation IV International Forum, created at the initiative of the US Department of Energy in 2000 to collaborate on research and development of advanced reactors to go into industrial operation around 2040. In 2002 the Forum chose six types of reactors on which to concentrate:  the gas-cooled fast reactor (GFR) Very-high-temperature reactor (VHTR), Supercritical-water-cooled reactor (SCWR), the Sodium-cooled fast reactor (SFR), the Lead-cooled fast reactor (LFR), and the Molten salt reactor (MSR),  

In January 2006 President Chiraq committed France to constructing a prototype of one type of Generation IV reactor.  The prototype, he stated, will go into operation in 2020.   

The reference reactor for the 2020 prototype is the sodium-cooled fast reactor.  Choices will need to be made in regard to the reactor's technological characteristics, including the power (between 250 and 600 MWe), the architecture, and the system for converting heat into electricity.  The CEA hopes that the options will be consolidated in 2009 and that, based on research conducted by the CEA, the government will in 2012 make final technological choices and decide to start construction.  It is intended that this reactor, when built, will participate in experiments in transmutation of minor actinides.  The reactor will be named Astrid.

The gas-cooled fast reactor is being studied in a European framework.  A decision to construct a small experimental reactor, likely outside France, may be reached in 2012.  The experimental reactor is likely to be cooled with helium and to operate at low power (50 MWth).  The reference fuel for the reactor is made of plates constructed of a honeycomb of silicon carbide in which tablets made of carbides of actinides are placed.  The recycling of actinides will be studied [CNE 2, 2007 and 2008].

                                                                                               --updated 10 December 2008