Nuclear fuel element

Since a great temperature gradient is caused in the radial direction of a fuel pellet, the upper and the lower ends of the pellet are extended outwardly and deformed into a saddle-like form, by which the end face of the pellet is brought into contact with a fuel can, to apply high stress and distortion to the fuel can. If nuclear fission products should exert on the stress-strained portion, the possibility of causing stress corrosion cracks is increased. Then, in the present invention, an aluminium thin film is formed as a second layer at the inside of a lined cladding tube comprising a pure zirconium layer disposed to the inner surface of a fuel can made of a zirconium-based alloy. This can protect the zirconium of the first coating layer and prevent selective corrosion due to corrosive fission products. Further, since aluminum is excellent in ductility and easily deformed, stress concentration can be moderated. (T.M.)