Some reactors (only one in commercial service) do not have a moderator and utilize fast neutrons, generating power from plutonium while making more of it from the U238 isotope in or around the fuel. These get more than 60 times as much energy from the original uranium compared with the normal reactors. These are expensive to build. Further development of them is likely in the next decade, and the main designs expected to be built in two decades are FNRs
