Metallic Fast Reactor Fuels

Metallic fuels are neutronically ideal for fast reactors because they produce an extremely hard neutron spectrum. Early metallic fuels had little endurance, due to excessive swelling. By incorporating space for swelling, very high burnups are now routinely achieved. Uranium-plutonium alloys with 10% zirconium to raise the melting point have been shown to be extremely reliable. Fuel swelling, mechanical and chemical interactions with various cladding materials, performance during transients, failure mechanisms, and behavior following both benign and complete failure of fuel pins have been extensively studied. The basic phenomena governing the performance of this type of fuel are well known, and have been sufficiently well modeled to specify design parameters that will assure reliable performance.