What is meant by nuclear fuel?
Nuclear fuel is any material that contains fissionable nuclides and can be used in a reactor to develop a nuclear chain reaction. According to this definition, uranium is a nuclear fuel, as well as uranium oxide. The former is a chemical element, some of whose isotopes are fissionable; the latter is a specific chemical compound containing these isotopes. Fissionable isotopes are understood to be those nuclides likely to undergo fission. To be more exact, it would be necessary to specify the energy of neutrons that can make the isotope fissionable; for example, U238 is not fissionable by thermal neutrons, but it is fissionable by fast neutrons, although with a low effective section. In the absence of a more precise definition, fissionable isotope is usually understood to mean any nuclide that will fission by the action of thermal neutrons. The only thermal neutron-fissionable isotope found in nature is uranium 235. Its proportion in natural uranium is 0.711 percent. There are other fiss
