“What is a breeder reactor?” A breeder reactor produces more material capable of sustaining a nuclear fission chain reaction than it consumes to generate energy. Using fission, atomic nuclei split into two or more smaller nuclei. This process converts a small amount of mass into energy. A breeder reactor utilizes uranium-238 or thorium, two readily available materials. The "breeding ratio" is the number of new fissile atoms created for each fission event. This helps us understand how much fissile plutonium-239 is created compared to the amount of fissionable fuel used to produce it. Ideally, the breeding ratio is 1:4 our results have been historically been about 1:2. Two fuel cycles breeder reactors use are: uranium-plutonium (fertile material