Patent ID: 7389669
Filing Date: 2008-06-24
Classification: C21D

Abstract:
1. A process for removing the residual tensile welding stresses in an inner layer of a weld metal and a heat-affected zone of a coupling between a pressurized water reactor pressure vessel nozzle and an intermediate transition pipe that spans between the pressure vessel nozzle and a primary coolant piping section, where the nozzle and the primary coolant piping section have each been butt-welded end-to-end to different ends of the intermediate transition pipe by means of circumferential welds, which process comprises: mechanically introducing circumferential compressive stresses in a first section on said transition pipe spaced from the weld between the pressure vessel nozzle and the intermediate transition pipe by applying a radial load inwardly on said first section; and mechanically introducing circumferential compressive stresses in a second section on the primary coolant piping section by applying a radial load inwardly on said second section; wherein the amount of said radial load being applied on said first and second sections is sufficient to permanently reduce the outside diameter at a midplane of the first and second sections in a range of about 0.2 to about 3.0 percent, the percent of permanent contraction at said midplane of said first and second sections upon which said radial loads are applied being greater than the permanent contraction at the midplane of the weld between the pressure vessel nozzle and the intermediate transition pipe, said inner layer at the weld location between the pressure vessel nozzle and the intermediate transition pipe assuming a concave configuration as a result of said application of said radial loads.