FBRs

FBRs, or fast breeder reactors, are a class of nuclear reactors that use fast neutrons for fission and employ a breeding blanket of fertile material to generate additional fissile fuel. Unlike conventional thermal reactors that rely on a moderator to slow neutrons, FBRs operate with fast neutrons, which enables the conversion of non-fissile isotopes such as uranium-238 into fissile plutonium-239 (and thorium-232 into uranium-233). A breeding ratio greater than one means the reactor produces more fissile material than it consumes, enabling a closed fuel cycle in which fuel is continually recycled.

Most FBR designs use a liquid metal coolant, with sodium being the most common choice, though lead and lead-bismuth are also used in some designs. They typically run on metallic or mixed-oxide (MOX) fuels and rely on reprocessing to separate plutonium and other actinides for reuse. The broad goal is to improve resource utilization by converting abundant fertile material into usable fuel and, in some designs, to reduce long-lived waste by transmuting certain actinides.

Historically, several nations pursued FBR programs, including France, Japan, Russia, and India. Demonstration and prototype reactors have informed domestic programs, with varying outcomes due to safety, cost, and proliferation concerns. Some projects have been scaled back or halted, while other programs continue research and development as part of broader strategies for sustainable nuclear energy and closed fuel cycles.

Safety and policy considerations are central to FBR development. Sodium coolant poses reactivity and fire risks if leaks occur, requiring robust containment and emergency systems. Proliferation concerns arise from fuel reprocessing to extract plutonium. Economic competitiveness, regulatory maturity, and public acceptance also influence the future deployment of fast breeder technology.