fast breeder reactor Nuclear reactor which uses fast neutrons to convert uranium to plutonium and which creates more fuel than it uses. A chain reaction is set up in which ²³⁸U, with an initial charge of ²³⁹Pu to begin the fission process, discards fast neutrons each of which induces fission in another nucleus. Excess ²³⁹Pu is produced where plutonium production exceeds rate of fission. About 60% of fuel elements in fast breeder reactors is converted to useful energy compared to 0.5–1% in burner reactors. Plutonium can be recycled, but other radioactive products are waste. See RADIOACTIVE WASTE.

fast breeder reactor A nuclear reactor that uses fast neutrons to convert uranium to plutonium and which creates more fuel than it uses. A chain reaction is set up in which ²³⁸U, with an initial charge of ²³⁹Pu to begin the fission process, discards fast neutrons, each of which induces fission in another nucleus. Excess ²³⁹Pu is produced where plutonium production exceeds rate of fission. In fast breeder reactors, about 60 per cent of the fissionable material in the fuel elements is converted to useful energy compared to 0.5–1 per cent in burner reactors. Plutonium can be recycled, but other radioactive products are waste. See radioactive waste.