Analyzing Fuel Bundle Deformation Using the Finite Element Method

Abstract

During off-normal or accident conditions, the temperature transient experienced by a fuel bundle may lead to deformation of the bundle via fuel element bowing between the spacer pads due to subchannel temperature gradients, or fuel element sagging under gravity. In these conditions, the deformation could impact the coolant flow distribution through the bundle, causing further degradation of the fuel cooling. The deformations of the fuel elements may also lead to fuel element contact with the pressure tube, leading to localised heating that may comprise the pressure tube integrity. The objective of this work is to create a three-dimensional finite element model to analyze bundle deformation behavior under transient conditions.