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A fast neutron reactor [abbreviated, FNR later in the next article. AKA, ‘fast reactor’] is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons. Such a reactor needs no neutron moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor.
In order to sustain a fission chain reaction, the neutrons released in fission events have to react with other atoms in the fuel. The chance of this occurring depends on the energy of the neutron; most atoms will only undergo induced fission with high energy neutrons, although a smaller number prefer much lower energies.
Natural uranium consists mostly of three isotopes, U-238, U-235, and trace quantities of U-234, a decay product of U-238. U-238 accounts for roughly 99.3% of natural uranium and undergoes fission only by neutrons with energies of 5 MeV or greater, the so-called fast neutrons. About 0.7% of natural uranium is U-235, which undergoes fission by neutrons of any energy.
[In an FNR n]atural uranium… is turned into several isotopes of plutonium during its operation. Two of these, Pu-239 and Pu-241, then undergo fission in the same way as U-235 to produce heat. In a FNR this process is optimised so that it 'breeds' fuel. Some U-238 is burned directly with neutron energies above 1 MeV. Hence FNRs can utilise uranium about 60 times more efficiently than a normal reactor.
Unit 4 of the Beloyarsk nuclear power plant in Russia has started commercial operation, state nuclear corporation Rosatom announced today. The BN-800 fast neutron reactor started operating at 100% power for the first time on 17 August.
The 789 MWe BN-800 Beloyarsk 4 is fuelled by a mix of uranium and plutonium oxides arranged to produce new fuel material as it burns. Its capacity exceeds that of the world's second most powerful fast reactor - the 560 MWe BN-600 Beloyarsk 3.
GE Hitachi Nuclear Energy (GEH) and Southern Nuclear are to collaborate on the development and licensing of [FNRs] including GEH's Prism sodium-cooled fast reactor, the companies announced yesterday.
Prism is a sodium-cooled fast neutron reactor design built on more than 30 years of development work…
Each Prism reactor has a rated thermal power of 840 MW and an electrical output of 311 MW. Two Prism reactors make up a power block, producing a combined total of 622 MW of electrical output. Using passive safety, digital instrumentation and control, and modular fabrication techniques to expedite plant construction, the design uses metallic fuel, such as an alloy of zirconium, uranium, and plutonium. It can therefore be used to close the nuclear fuel cycle, recycling used nuclear fuel to generate energy.
Most of these designs are generally not expected to be available for commercial construction before 2030–40.
The BN-800 reactor is a sodium-cooled fast breeder reactor, built at the Beloyarsk Nuclear Power Station, in Zarechny, Sverdlovsk Oblast, Russia. Designed to generate electrical power of 880 MW in total, the plant is the final step to the commercial plutonium cycle breeder. The plant reached its full power production in August, 2016.
Such a reactor needs no neutron moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor.