Coupled physics simulation of fracture in nuclear fuel pellets induced by resistive heating

Separate-Effects Tests for Studying Temperature-Gradient-Driven Cracking in UO2 Pellets

“…This thermal gradient as shown in Figure 9, drives the radial cracks to propagate axially until they meet the axial cracks, at which point the pellet is completely fractured. The formation of significant axial cracks in the experiments as shown in Figure 8, is reasonably consistent with the predictions of Yeh et al [9]. As previously mentioned, those simulations employed 2D planar models, and only predict the extent of axial cracking at a given location in the cross-section, and not the number or location of axial cracks along the axis of the pellet.…”

“…Since the current is passed transversely across the pellet, there is significant spatial variation in the current density across the pellet cross-section. Preliminary two-dimensional (2D) BISON simulations conducted by Yeh et al [9] show that the temperature contours of the experiments conducted in this study were oblong as opposed to the circular shape that would be seen in a reactor environment. Because of the nature of these oblong temperature contours and the resulting thermally induced stresses, Yeh et al [9] predicted that most radial cracks would initiate near the electrodes and propagate inward, while axial cracks would initiate at azimuthal locations at 90°…”

“…As long as the computational models can replicate the experimental environment, these experiments can be used for validation of those models. The experimental data has been used in a parametric study conducted by Yeh et al [9] encompassing electrical conductivity and heat transfer coefficients where the temperature and cracking data from these experiments were successfully implemented in validating the 2-D cracking model in BISON.…”

“…The data collected will be used in the validation of UO2 cracking models in BISON. In the meantime, the experimental results were used for successfully validating 2-D UO2 cracking models in BISON [9]. The 3-D cracking models' validation is currently a work in progress.…”