Transmutation of actinides: fast neutrons are most effective
Fast neutrons are effective at destroying the heavy nuclei present in reactors, including those that are supposedly not fissile. Here the probability of fission of the isotopes of plutonium and the minor actinides using slow neutrons in a classic PWR reactor is compared with the probability using fast neutrons in a hybrid reactor. With fast neutrons, all the elements have a good chance of being eliminated by fission. The effectiveness of the fast neutrons is due to the extra energy supplied by their kinetic energy, which makes the fission of fragile nuclei easier.
IN2P3 (Source: ORNL-4628 PWR spectrum and energy amplifier)