Nuclear fuel is fissionable material of reasonably long life, used or usable in producing energy in a nuclear reactor. Nuclear fuel consists of various chemical and physical forms of uranium and plutonium. Fluid fuels are required in homogeneous reactors; heterogeneous reactors use various forms of fuels – pure metals or alloys, as well as oxides or carbides. The fuel must have a high thermal conductivity, be resistant to radiation damage, and be easy to fabricate.
In accordance with the definition of the Atomic Energy Act, nuclear fuel consists of special fissile substances in the form of
plutonium-239 and plutonium-241
uranium with the isotopes U-235 or U-233 enriched
substances containing one or several of the aforementioned substances
substances with the aid of which a self-perpetuating chain reaction can be upheld in a suitable plant (reactor) and which are determined in an ordinance having the force of law
nuclear fuel enrichment
Enrichment is the separation of the fissionable isotope of uranium, uranium-235, from the more abundant uranium-238 isotope. Gaseous uranium (VI) fluoride undergoes diffusion separation using cascades of barriers with microscopically small pores. The difference in mass between the two isotopes is minimal, but sufficient so that the heavier, slower-moving uranium-238 molecules are concentrated on one side. High-speed centrifugal-force separation methods are also used.