Production method of spacer for fuel assembly

Spacer constituent materials such as a spacer/cell and a spacer/band, both made of zirconium alloy are assembled by welding to manufacture spacers for a fuel assembly. In this case, after completion of the assembling operation by welding, a so-called β -quenching treatment is applied by keeping at a solid-solubilizing temperature to completely solid solubilize inhomogeneous tissues of the weld portion of the spacer constituent materials to a base material (β -phase), and then cooling the same rapidly. Accordingly, the weld portion of the spacer has the same tissue as the fuel element cladding tube already applied with β -quenching. Therefore, a production of a local cell between the spacer weld portion and the fuel element cladding tube is prevented. If a fuel assembly is constituted while supporting the fuel element cladding tubes by the thus formed spacers, electrochemical corrosion of the fuel element cladding tube can be prevented during reactor operation. Accordingly, safety can be improved. (I.N.)