This research investigates the Flow-Induced Vibration (FIV) of a fuel rod within a fuel assembly using a novel technique to reduce the computational cost. In partitioned Fluid-Structure Interaction (FSI) problems, in high-density fluids because of strong interaction between the fluid and the structure, fulfilling the boundary conditions is likely to fail due to oscillatory convergence or even divergence, and especially shell geometry exacerbates the situation. Either ramping or Under-Relaxation (UR) or both will help avoid the failure but instead leads to additional numbers of coupling iteration, and therefore repeatedly solution ofsolvers. As a novelty, an equivalent (EQ) rod model is introduced to simplify modeling of a fuel rod’s complex geometry. The model makes under-relaxation and ramping algorithms unnecessary, or at least lessens the number of the Supplementary Coupling Iterations (SCI).To prove this, three benchmark problems have been investigated. The first one studies theFIV of a brass rod in anannularduct and the second one studies the FIV ofa shell bundle exposed to axial flow. Finally, the modal characteristics of a typical fuel rod is determined. Results reveal that EQ rod is applicable to boiling water reactors and pressurized water reactors although for fluids much denser than water as it is in heavyliquidmetal cooled reactors, the results are slightly different.