Fast breeder reactors are a type of nuclear reactor that generate more fissile material than they consume. They use fast neutrons to sustain the nuclear fission process, allowing them to convert non-fissile isotopes, like uranium-238, into fissile isotopes, such as plutonium-239. This makes them efficient in utilizing nuclear fuel. These reactors can help address the issue of nuclear waste by recycling spent fuel and reducing the amount of long-lived radioactive materials. Additionally, fast breeder reactors can contribute to energy sustainability by extending the availability of nuclear fuel resources, making them an important part of future energy strategies.