To achieve adequate corrosion resistance in high-temperature water, the chemical composition and fabrication of zirconium cladding material must be carefully controlled. Present technology permits the satisfactory fabrication of a variety of fuel materials which are compatible with zirconium cladding. Homogeneity and melting crucible problems still exist with some of the fuel alloys. Zirconium-clad fuel elements of the bonded type are produced by pack rolling or coextrusion of the fuel and cladding. The optimum working temperature represents a balance between the need for minimizing differences in plasticity between fuel and cladding and for adequate diffusion at the clad-fuel interface. Unbonded fuel elements require close dimensional control of fuel and cladding and high-quality closure welds which are made possible by the excellent welding characteristics of Zircaloy.