Study of Tornado Missile Impact Mitigation for Nuclear Safety-Related Piping Using Viscous Damper Supports

External safety-related piping in nuclear power plants may be exposed to tornado missile impact, resulting in local indentation, global bending deformation, and transient support responses, which may threaten the structural integrity and safety functions of nuclear power plants. Existing pipe impact studies have mainly focused on failure behavior under idealized or prescribed boundary conditions, while the application of viscous damper supports remains limited. In this study, a three-dimensional nonlinear finite element model of a pipe-support system is established in Abaqus. The model is used to investigate the effects of support type, damper parameters, support stiffness ratio, pipe span, and wall thickness on impact response and energy dissipation. The results show that support flexibility accounts for the major reduction in global bending relative to rigid supports, while viscous dampers further reduce support displacement and velocity and provide additional energy dissipation. In the benchmark case, the viscous damper support reduces peak global bending by 78.9% compared with the rigid support, and reduces peak support displacement and velocity by 55.6% and 54.5%, respectively, compared with the elastic support. Its influence on local indentation remains limited. These findings indicate that viscous damper supports mitigate impact responses primarily by controlling support motion and altering the energy dissipation behavior of the pipe–support systems, rather than by directly suppressing local indentation. This study provides a reference for support layout and parameter selection of external safety-related piping subjected to tornado missile impact.