Which is the Fast-Neutron Reactor that uses no moderator, uses fast neutrons, and generates plutonium from natural uranium?

Which is the Fast-Neutron Reactor that uses no moderator, uses fast neutrons, and generates plutonium from natural uranium?

• A. Candu Reactor
• B. Magnox Reactor
• C. AGR Reactor
• D. FNR Reactor

Answer: (D)

Fast-neutron reactors operate with a spectrum of neutrons that stay fast, so no moderator is used to slow them down. This fast environment lets the reactor both sustain fission with fast neutrons and breed new fissile material from natural uranium, specifically transforming U-238 into Pu-239 through neutron capture and subsequent beta decays. Because of this no-moderator, fast-neutron design and the natural-uranium fuel cycle, it’s the type that fits all parts of the description: fast neutrons, no moderator, and plutonium production from natural uranium. The other reactor types rely on moderators (such as graphite or heavy water) to slow neutrons to thermal energies, which changes the neutron spectrum and the fuel dynamics. They may use natural or slightly enriched fuels, but they do not operate as fast-neutron breeders, so they don’t match the criteria as well.

Fast-neutron reactors operate with a spectrum of neutrons that stay fast, so no moderator is used to slow them down. This fast environment lets the reactor both sustain fission with fast neutrons and breed new fissile material from natural uranium, specifically transforming U-238 into Pu-239 through neutron capture and subsequent beta decays. Because of this no-moderator, fast-neutron design and the natural-uranium fuel cycle, it’s the type that fits all parts of the description: fast neutrons, no moderator, and plutonium production from natural uranium.

The other reactor types rely on moderators (such as graphite or heavy water) to slow neutrons to thermal energies, which changes the neutron spectrum and the fuel dynamics. They may use natural or slightly enriched fuels, but they do not operate as fast-neutron breeders, so they don’t match the criteria as well.