Fast reactors are a type of nuclear reactor that operate using high-energy (fast) neutrons instead of slowing them down with a moderator. Unlike thermal reactors, they do not require neutron moderation.
Key Characteristics:
- No moderator is used, allowing neutrons to retain their high kinetic energy.
- Designed to use fast neutrons to sustain the fission chain reaction.
- Typically use fuels enriched in uranium-235 or plutonium-239 to maintain reactivity with fast neutrons.
Advantages:
- Can breed more fuel than they consume by converting fertile material like uranium-238 into fissile plutonium-239 (hence also called breeder reactors).
- More efficient use of nuclear fuel, extracting more energy from the same amount of material.
- Can potentially burn long-lived radioactive waste, reducing the burden of nuclear waste disposal.
Coolants:
- Use coolants that do not slow neutrons, such as:
- Liquid sodium
- Lead
- Gas (like helium)
In essence, fast reactors are advanced nuclear systems that leverage the high energy of fast neutrons to improve fuel utilization, reduce waste, and potentially support a more sustainable nuclear fuel cycle.