Sodium-cooled fast reactors (SFR)
Safety approach of generation IV nuclear reactors

SFRs are fast neutron spectrum reactors, i.e. without moderator; the heat produced in the core is extracted by a molten metal, sodium. Compared with thermal neutron spectra, a fast neutron spectrum enables natural uranium (uranium 238), a "fertile" material, to be converted more efficiently into plutonium, a "fissile" material, enabling the SFR to be used in breeder mode, or, conversely, for increased plutonium consumption.

In SFRs, the power density in the core is very high: it can be of the order of 300 MW/m³, a value to be compared with around 100 MW/m³ for pressurized water reactors in the French nuclear power fleet. The maximum temperature of the sodium when the reactor is operating is around 550°C,...