PURPOSE: To provide a zirconium based alloy excellent in corrosion resistance and suitable as a material for fuel cladding pipe or a core structure such as a channel box or a spacer.

CONSTITUTION: In the production process of a fuel cladding pipe made of zircaloy, an alloy of Zr added with 0.5-2.0wt.% of at least one kind of Y and Pb with at least 1wt.% thereof being present in the form of solid solution, is employed as the compositional material for an original pipe 1.