Finite Element Simulations of a Fuel Element Simulator Sagging Experiment

Abstract

Finite Element Simulations of a Fuel Element Simulator Sagging Experiment A.F. Williams, S. Yatabe, and A. Belov In the IEC-I-1 test, an internally heated CANDU fuel element simulator was subjected to five temperature transients: three to a sheath peak temperature of 600°C, followed by two further transients to a sheath temperature of 800°C. The element was simply supported at the ends, and during the test the element sagged under its own weight by over 7 mm at the midpoint. A detailed 3D finite element model of this experiment was created using the ANSYS finite element software package. The model includes fuel pellets and sheath as separate components that interact via contact elements. The major deformation process for this experiment is creep of the zircaloy sheathing. The model was successful in determining the amount of deformation, despite the complexity of the many interacting components and the non-linear nature of the creep mechanism. The study included a detailed sensitivity study of a number of model parameters, including pellet-to-sheath friction, contact penalty function, rigid body damping (opening stiffness), time step size and the creep rate ratio limit.