A Fast Neutron Reactor (FNR) is a type of nuclear reactor that uses fast neutrons to sustain the fission process. Unlike traditional reactors that use slow neutrons, FNRs can efficiently utilize a wider range of nuclear fuels, including plutonium and uranium. This allows for better fuel efficiency and the potential for recycling nuclear waste. FNRs are designed to generate more fissile material than they consume, a process known as breeding. This capability can help address concerns about nuclear fuel scarcity and reduce the amount of long-lived radioactive waste produced. Overall, FNRs represent a promising technology for sustainable nuclear energy.