A STUDY OF THE FORMING OF ZIRCALOY-2 HEMISPHERES BY POWER SPINNING

S>Twelve Zircaloy-2 sheets, with thicknesses between 1/8and 5/16-in., were formed into 15-in.-diameter hemispheres by power spinning in an effort to determine the feasibility of using such a method to fabricate core vessels for the Homogeneous Reactor Project (HRP). The fabrication of an entire hemisphere as a unit is of interest because it would reduce the number of welds required to form a vessel. This in turn, would reduce the chance of weld contami nation and consequent impairment of corrosion resistance and mechanical properties. A number of difficulties such as laps and earing, were encountered but were overcome by modifications of the procedure. The maximum percentage of reduction in shell thickness was between 30 and 40%. The springback on the equatorial radius increased with thickness from 0.040 to 0.175 in., whereas the diametral ellipticity varies between 0.016 and 0.100 in. Three complete spheres were welded in a vacuum chamber using a technique developed by the vendor. Although the welding was not quite of HRP quality, it demonstrated that the spun shells could be assembled into vessels. (auth)