Eventos Anais de eventos
COBEF 2017
Congresso Brasileiro de Engenharia de Fabricação
NUMERICAL ANALYSIS OF FRETTING PROBLEM IN FUEL ROD OF A PWR NUCLEAR REACTOR
Submission Author:
Silvana Carreiro de Oliveira , RJ
Co-Authors:
Césio Túlio Alves dos Santos, Luiz Carlos Rolim Lopes
Presenter: Silvana Carreiro de Oliveira
doi://10.26678/ABCM.COBEF2017.COF2017-0046
Abstract
One of the major causes of failure in a nuclear plant is the fretting problem in the fuel rod. Due to this, several experimental studies have been conducted in the last years to observe more about the phenomenon and predict when and in what location of structure fretting failure can possibly happens. One of the frequent occurrence of fretting in PWR nuclear reactors is the contact region between the spacer grid and fuel rod and happens because of flow-induced vibration. This work aims to characterize this region of contact through the finite element method, with the help of Abaqus application. For this, a simplified model of PWR fuel assembly was used and fretting simulations was performed for different rod displacement. In the model definition, the properties of the spacer grid and the fuel cladding materials (Inconel-718, produce by cold rolling and machining and the Zircaloy-4, made by extrusion, respectively) were used. Simulations allowed obtaining the stress state at the contact region, such as contact pressure and shear stress distribution along the contact surface, the size of this contact and the stick region for each different situation. To validate the model, a comparison between the numerical results obtained in computer simulation and the theoretical results derived from formulas of contact mechanics; mainly by the Hertz contact theory was done. In the contact region with the springs, the numerical results for the contact size changed by 10% and for the contact pressure, this variation was around 30% compared with the theoretical results. In the contact region with the dimples, the variation of the contact size was 10%, while the variation of the contact pressure ranged 20%. This comparison showed that the numerical results are in agreement with the theory, making the model valid.
Keywords
fuel fretting, Finite Element Method, contact mechanics
