Thermo-mechanical analysis of a nuclear spent fuel dry cask using CFD results in a FE code

Abstract

As the pools in nuclear power plants are reaching their full capacity, the use of dry cask systems to store the spent fuel is growing. This leads to an increasing need of a better understanding of nuclear spent fuel behavior during its storage phase in dry casks, ultimately, ensuring that the safety limits are not compromised. Previous computational fluid dynamic (CFD) studies have found that the gap size between the canister and the basket have a remarkable impact on the fuel peak cladding temperature. However, because the exact gap size is usually unknown, this is routinely modelled as a constant thermal resistance between the components or it is not considered directly. On the other hand, the non-uniform temperature distributions in the components are expected to affect differently the gaps, through the non-uniform thermal displacements of the casks components. In turn, the possible reduction or increase of the gaps will affect the thermo-hydraulic performance of casks.In this paper, a thermo-mechanical analysis of a spent fuel dry cask is presented. The temperatures of the cask’s components obtained in a previous CFD simulation with STAR-CCM+ code are employed in the finite element code ABAQUS with the aim to study the overall behavior of the cask components. Additionally, a detailed analysis of the gaps is performed to help improving future CFD studies. The results presented in the paper confirm that the thermal displacements and stresses are relatively low, as compared to safety limits. The non-uniform relative displacements of the components obtained in the analysis of the gaps have facilitated explaining the differences in fuel temperatures between CFD simulations and experiments.