Nuclear fuel can

Purpose: To maintain the integrity of a fuel can even if fuels are burnt to high degree. Constitution: Liner layers surface coated with metal such as copper or zirconium are disposed on the surface of a zirconium alloy substrate in contact with nuclear fuel materials. Then, the difference between the average crystal size of the zirconium-based alloy for the substrate of the metal tube and the average particle grain size of the liner layer is reduced by way of a predetermined heat processing step. That is, if the average crystal grain size of the liner layer is between 5 μm and 10 μm, the average crystal grain size of the substrate is made more than 5 μm, if the average crystal grain size of the liner layer is between 10 μm and 15 μm, the average crystal grain size of the substrate is made greater than 8 μm, if the average grain size of the liner layer is between 15 μm and 20 μm, the average crystal grain size of the substrate is made greater than 9 μm, while the average crystal grain size of the substrate is made more than 10 μm, in a case where the average crystal grain size of more than 20 μm in the liner layer. (Seki, T.)