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What is a Sodium-cooled Fast Reactor?
The concept of a Sodium-cooled Fast Reactor (SFR) is a trailblazer in the nuclear industry. Their story began when scientists thought, “What if we use liquid sodium instead of regular water to cool the reactor and generate energy?”. This bold idea took shape in the mid-20th century, and since then, SFRs have been making waves in the world of nuclear technology.
Fast Neutrons
A sodium-cooled fast reactor (SFR) uses the fast neutron spectrum – neutrons with an average energy in excess of 1 MeV. Therefore, no moderator is required.
Molten Metal Coolant
Commonly, a sodium-cooled fast reactor uses liquid sodium metal as a coolant because of its great thermal properties, including high boiling point (882.8 °C) and excellent conductivity (for heat transfer). Furthermore – sodium’s only stable isotope, sodium-23 (23Na), is a very weak neutron absorber, this helps to ensure the neutrons stay fast!
Using a liquid metal as a coolant allows the reactor core to operate at a higher temperature but without the need for high pressure – increasing efficiency of power generation and improving safety.
Fertile Fuel
In a sodium-cooled fast reactors, it is common to use a mixed oxide fuel comprising uranium dioxide (UO2), plutonium dioxide (PuO2) and sometimes other actinides too. This is facilitated by the use of the fast neutron spectrum enabling use of fertile fuels, based upon isotopes such as uranium-238 (238U) which can adsorb a fast neutron and convert into the fissile isotopes plutonium-239 (239Pu).
Alternatively, some experimental SFR designs use metallic fuels such as an alloy of uranium, plutonium and zirconium.
Development of Sodium-cooled Fast Reactor Technology
History of the Sodium-cooled Fast Reactor
Initial development of sodium-cooled fast reactor designs commenced during the mid-20th century as part of efforts to develop breeder reactors that could maximise fuel use and reduce nuclear waste, with early prototypes like emerging from the USA, France and Soviet Union. This included Superphénix, a French SFR prototype that was decommissioned in 1977.
What is happening today?
Countries like France, Japan, and Russia have been leading the charge, collaborating to improve and perfect Sodium-cooled Fast Reactor technology. What makes SFRs special is their ability to use fast neutrons, which are like the speedy messengers inside the reactor, making the whole process more efficient. This advantage is shared by other designs based upon molten metal cooling, such as a lead-cooled fast reactor.
Though SFRs aren’t currently operating anywhere commercially, scientists are working on smaller versions to test their potential. It’s like a sneak peek into the future of energy. By the next decade, we might witness the rise of sodium-cooled fast reactors, bringing us a new era of nuclear power that’s both reliable and forward-thinking.
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