Flow-induced vibration analysis of nuclear fuel rods using equivalent fuel element model

• Published in: Nuclear engineering and design 2020-07, Vol.363, p.110639, Article 110639
• Main Authors: Nazari, Tooraj, Rabiee, Ataollah, Kazeminejad, Hossein
• Format: Article
• Language: English
• Subjects: Algorithms; Axial flow; Boiling water reactors; Boundary conditions; Computational fluid dynamics; Computer applications; Coupling; Equivalence; Equivalent fuel rod; Flow generated vibrations; Fluid-structure interaction; Heavy metals; Iterative methods; Liquid metal cooled reactors; Modal characteristics; Nuclear energy; Nuclear fuel elements; Nuclear fuels; Nuclear reactors; Pressurized water reactors; Reactors; Solvers; Strong interactions (field theory); Vibration; Vibration analysis
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2020.110639

•The EQ rod model simplifies the complex geometry of fuel rods in FSI problems.•The technique reduces the computational costs in FIV problems.•The method overcomes divergence problems for the structural large deformation. 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.