Application of Hydrostatic Extrusion to Fabrication of Zircaloy Tubing

Abstract

Preliminary experiments in the extrusion of Zircaloy tubing using both cold and hot hydrostatic extrusion processes were carried out. In the cold hydrostatic extrusion, a maximum extrusion ratio of five could be obtained, but it should be limited to a maximum of three to prevent the occurrence of galling. When the cold hydrostatic extrusion process was applied to the final pass of cold reducing, the properties of the obtained tubes were nearly identical to those of the current boiling water reactor cladding tubes in spite of the difference of the crystallographic texture of the tubes. Application of the newly developed hot hydrostatic extrusion process to the extrusion of tube shells resulted in an increase of the extrusion ratio to three times that of the conventional direct extrusion. The tubing processed from hydrostatically extruded tube shells at the higher extrusion ratios showed higher strength and lower ductility than those of lower extrusion ratios in the tension tests. In the case of the burst tests, however, the ductility was higher in the tubes processed from the tube shells of the higher extrusion ratios.