Mass, stiffness, and damping identification for a pressurized water reactors fuel assembly by a proper orthogonal decomposition method

In this paper, dynamic tests of a fuel assembly subjected to an axial flow are presented. Tests are performed for various flow conditions, at several displacement amplitudes. The first four modes of the fuel assembly are excited, two confinements are tested. A parameters identification method based on a proper orthogonal decomposition (POD) analysis is proposed. Mass, damping, and stiffness parameters are presented for different displacement amplitudes and flow rates. An added mass effect in still water is observed, and the damping increases linearly with the flow rate. A nonlinear behavior of the fuel assembly is observed. An added stiffness effect increasing with the flow rate is observed, and the mass seems to depend on the flow rate. The by-pass seems to be responsible for these observations. (authors)