| Description |
This study evaluates the structural integrity of spent nuclear fuel (SNF) rods under impacts caused by accidents during transportation. SNF rods consist of uranium dioxide fuel pellets encapsulated in a zircaloy cladding tube. The linear and nonlinear buckling analysis of a typical 532 mm (21 in.) long fuel rod segment is performed in finite element software Abaqus, under static loading conditions. Initially, the analysis is carried out for a vertical end drop, including an initial imperfection of 0.1 mm in the model. Thereafter, impact drops are evaluated with the fuel rod at different orientations. The results indicate that pellets significantly stiffen the fuel rod when its orientation is nearly vertical. However, the pellet contribution decreases significantly as the orientation angle at impact increases. The effect of pellet-cladding interaction (PCI) on the buckling performance of the SNF rods is also studied. The results indicate that the PCI composite action is partially retained even for relatively large rod impact angles with respect to the vertical direction. The inelastic buckling controls the buckling behavior of the fuel rods with lower slenderness ratio. Therefore, the effect of degradation mechanisms of the irradiated clad after long-term storage are considered on the buckling behavior of 252 mm (10 in.) and 140 mm (5.5 in.) fuel rod segments. The study concludes that long-term degradation only affects the 140 mm simply supported fuel rod segment, length equivalent to the end cantilever segment. However, this segment is not expected to fail because its buckling capacity is one order of magnitude higher than that of a typical 532 mm segment. |
