Type of nuclear reactor using ²³⁵U as fuel. Enriched uranium is used to increase efficiency. To prolong the fission reaction, fast neutrons are slowed down with a moderator (graphite or heavy water) and the rate of reaction is adjusted by control rods (boron) which can absorb neutrons. Some neutrons react to form plutonium, but in smaller amounts than the original uranium, hence the term burner reactor. Compare fast breeder reactor.