Study On Flow-Induced Vibration Response Of Reactor Internals

Research on flow-induced vibration of reactor internals is of great significance to the safety of nuclear energy development.Based on numerical simulation method,the flow-induced vibration response of reactor internals is studied in this paper.The main contributions of this paper are as follows:1.The finite element models of the reactor core barrel and whole reactor internals are established by using the ANSYS software,respectively.And the dynamical characteristics of reactor internals vibrating in both air and still water are analyzed.Results show that the natural frequencies of the reactor internals vibrating in still water are lower than those in air.The first several order natural frequencies of the structure are related to the beam-type and shell-type frequencies.Moreover,compared with the beam frequencies,the shell frequencies of the reactor internals are strongly affected by the added mass of the fluid.2.Based on CFD the software,the LES turbulence model is used to simulate the fluid field of the reactor internals.And the turbulence characteristics of the flow are mainly considered.The turbulence pulsation forces on the outer surface of the core barrel are used as the input of the reactor internals~'response calculation.Results show that the vibration responses of the core barrel are featured by the coupled vibration of one-order beam-type and shell-type(1,2),and its maximum displacement response is appeared in the middle of the generating line at the entrance of the core barrel.3.In view of the difficulty that in charatering the fluid force distribution on the outer surface of the core barrel is difficult to be characterized by fewer measurement points in the scaled model test,a simple time domain method based on the simulation fluid force is proposed in this paper,which combines the arrangement of measuring points in a row in the model test of reactor internals.Because it is difficult to characterize the fluid force distribution at the entrance position by using the layout of the measuring points,the additional measuring points at the entrance position is considered.The response of the reactor internals under the fluid force simulated by adding a row of measuring points in one circle is compared with that under the fluid force simulated by the full simulation.It is shown that the response obtained by adding the inlet fluid force measurement points shows a better agreement with the response under the full simulation fluid force.4.In order to investigate the effects of inlet fluctuating velocity on reactor internals response,a Fluent UDF program was developed to control the inlet velocity,and the reactor internals response under fluctuating flow was obtained.Results show that with the pulsating flow,the frequency components of reactor internals contain the frequency of inlet pulsating flow velocity.When the frequency of pulsation is close to the first-order beam-type frequency of the core barrel in still water,the response is dominated by the first-order beam-type vibration,and the bottom response of the core barrel increases greatly.