Effect of bending on the geometry and collapse pressure of helical steam generator tubes: Numerical study

This study investigates the effects of bending processes on the geometry and collapse pressure of helical steam generator tubes used in Small Modular Reactors (SMRs). The bending process induces geometric imperfections such as ovality and eccentricity, as well as work hardening, which significantly impact the structural integrity of the tubes. Finite element analysis, employing an implicit numerical scheme, was used to simulate the multi-roller bending process, considering three different curvature radii and varying tube thicknesses. The results indicate that thicker tubes exhibit higher eccentricity, while thinner tubes show increased ovality. Additionally, the collapse pressure was found to increase with tube thickness and the degree of plastic deformation. By applying an implicit finite element scheme to simulate the multi-roller bending process, this study captures realistic geometric imperfections and work hardening effects that are often overlooked in prior studies. These findings contribute to improving the accuracy and reliability of the design and manufacturing of helical steam generator tubes in nuclear reactors.