During off-normal conditions, the temperature transient experienced by a CANDU fuel bundle may lead to deformation of the bundle via fuel element bowing between the spacer pads due to sub-channel temperature gradients, or fuel element sagging under gravity. The resulting deformation could impact the coolant flow distribution through the bundle, causing further degradation of the fuel cooling. Moreover, the deformation of the fuel elements may also lead to contact with the pressure tube, leading to localized heating that may compromise the integrity of the pressure tube. The objective of this work is to create a 3D finite element model to analyze bundle deformation behaviour under transient conditions. The methodology and preliminary results are presented herein.

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