Fuel element

Object: To prevent entry of nuclear fission fragments having high kinetic energies into a cladding material to avoid a failure of the cladding material. Structure: An outer peripheral surface of a fissionable material or an alloy containing said material is surrounded with at least one kind of auxiliary cladding material for absorbing nuclear fission fragments selected out of Zr, Nb, Mo, Mg, Al, Ti, Fe, Zn, Sn, Cu, etc., and said cladded material is further coated in its outer periphery with a main cladding material. (Kamimura, M.)