Journal article Open Access

Neutronic simulation of fuel assembly vibrations in a nuclear reactor

A. Vidal-Ferrandiz; A. Carreno,; D. Ginestar; C.Demazière; G.Verdu

The mechanical vibrations of core internals as fuel assemblies cause oscillations in the neutron ux that require, in some circumstances, to operate nuclear power plants at a reduced power level. This work simulates and analyses the changes of the neutron ux throughout a nuclear core due to the oscillation of a single fuel assembly without considering thermal-hydraulic feedback. The amplitude of the fuel assembly vibration is bounded to a few millimeters and this implies the use of ne meshes and accurate numerical solvers due to the different scales of the problem. The results of the simulations show a main oscillation of the neutron ux with the same frequency as the fuel assembly vibration along with other harmonics at multiples of the vibration frequency much smaller in amplitude. Also, this work compares time-domain analysis and frequency-domain analysis of the mechanical vibrations. Numerical results show a close match between these two approaches for the fundamental frequency.

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