Abstract
Spent nuclear fuel (SNF) is nuclear fuel that has been irradiated and discharged from nuclear reactors. During the whole management stages of SNF before it is, in the end, disposed in a deep geological repository, the structural integrity of fuel rods and the assemblies should be maintained for safety and economic reasons. In licensing applications for the SNF storage and transportation, the integrity of SNF needs to be evaluated considering various loading conditions. However, this is a challenging task due to the complexity of the geometry and properties of SNF. In this paper, a simple and equivalent analysis model for SNF rods is developed using model calibration based on optimization and process integration. The spent fuel rod is simplified into a hollow beam with a homogenous isotropic material, and the model parameters thus found are not dependent on the length of the reference fuel rod segment that is considered. Two distinct models with different interfacial conditions between the fuel pellets and cladding are used in the calibration to account for the effect of PCMI (Pellet-Clad Mechanical Interaction). The feasibility of the models in dynamic impact simulations is examined, and it is expected that the developed models can be utilized in the analysis of assembly-level analyses for the SNF integrity assessment during transportation and storage.
Highlights
The Spent nuclear fuel (SNF) (Spent Nuclear Fuel), which is the discharged nuclear fuel after irradiation in a nuclear reactor, should be carefully managed due to its strong radioactivity and toxicity
It is noted that the SNF with a burnup greater than 45 GWd/MTU is categorized into high burnup fuel (HBF), whose characteristics are distinctively different from those of low burnup fuels
In areal pureHBF, bending, thealso loading are implemented with relevant keywords in and bonds form condition is consistent throughout the length of the fuel rod, and it is expected that material properties between fuel pellets, but these bonds are not considered in this work
Summary
The SNF (Spent Nuclear Fuel), which is the discharged nuclear fuel after irradiation in a nuclear reactor, should be carefully managed due to its strong radioactivity and toxicity. The cladding serves as the first barrier preventing the release of radioactive materials into the environment For this reason, the integrity of SNF and cladding should be carefully evaluated during the licensing process of SNF transportation and storage, and it is enforced by safety regulations [2,3,4]. The SNF rods are often simplified into beams with degenerated section and material properties This model simplification procedure is not simple due to the complicated composite behavior of fuel pellets and cladding with uncertain interfacial conditions. In the work of Lee and Kim [24], the material properties of the equivalent beam model of the SNF rod was found using optimization, considering two distinct interfacial conditions. The beam models found are examined in dynamic impact simulations to check their applicability in the assessment of fuel rod failure under accident conditions
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