Nonlinear vibrations of a 3 × 3 reduced scale PWR fuel assembly supported by spacer grids

Franchini, Giulio; Faedo, Luca; Giovanniello, Francesco; Guisquet, Stanislas Le; Balasubramanian, Prabakaran; Karazis, Kostas; Amabili, Marco

doi:10.1016/j.nucengdes.2020.110674

Cited by 19 publications

(1 citation statement)

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“…Te fuel assembly is simplifed into a dynamic model whose dynamic characteristics need to be calibrated by experiments. Many kinds of tests exist in the literature that have studied these dynamic characteristics, such as the pluck test (or snap back test without impact) [1][2][3][4], swept sine excitation test [1,2,[4][5][6][7], step-sine harmonic excitation test [8,9], and broadband pseudorandom excitation test [2,8,9]. However, the pluck test is the easiest and most convenient method.…”

Section: Introductionmentioning

confidence: 99%

A New Experimental Method for the Nonlinear Modal Parameter Identification of a Pressurized Water Reactor Fuel Assembly

Yang

Guo

et al. 2023

Science and Technology of Nuclear Installations

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Establishing a dynamic model that accurately describes a realistic pressurized water reactor (PWR) fuel assembly is crucial to precisely evaluate the mechanical properties of the fuel assembly in seismic or loss of coolant accidents (LOCAs). The pluck test combined with the logarithmic decrement method has been widely applied in previous studies to extract fundamental modal parameters to calibrate dynamic models. However, most previous investigations focused on the first cycle of free vibration, which is strongly affected by stiction, baseline shift, drop conditions, and high-order mode interference, leading to inaccurate results. Moreover, these traditional methods cannot be used to extract high-order modal parameters. In this work, a novel experimental method for identifying the nonlinear modal parameters of a PWR fuel assembly is proposed. First, two algorithms are adopted to decompose the free vibration. Second, the local linearized modal parameters are extracted by a single-degree-of-freedom fitting method with a sliding window. Finally, these local linearized modal parameters are summed to obtain the nonlinear relationships between the modal parameters and amplitude. The new method makes more effective use of experimental data, obtains more accurate modal parameters than the logarithmic decrement method, and is capable of extracting high-order modal parameters. In the end, the test results are fitted by a fractional polynomial, which is of great value for numerical simulations.

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