Nuclear spent fuel cask full scope simulation using coupled Computational Fluid Dynamics models

The interest in medium to long-term nuclear spent fuel storage is growing worldwide. After being cooled during several years in the spent fuel pool, the fuel can be stored in dry casks in a second phase, being moved to a temporary repository for the mid-term and/or into a deep storage facility for the long-term. To ensure the fuel integrity, the peak cladding temperature (PCT) is a common safety parameter. The PCT can be estimated by performing simulations, and Computational Fluid Dynamics (CFD) codes have been widely used for this purpose. In this paper, the commercial CFD code ANSYS CFX 2019 R3 has been used to estimate the PCT in a generic spent fuel dry cask of 32 fuel elements. Although CFD codes are useful tools for that purpose, they also have drawbacks, mainly their computational cost to perform complex simulations. To overcome this issue, a methodology which splits the simulation in two separated but coupled models has been used, significantly reducing the required hardware. The results shown an adequate behavior of the fluid flow together with a best estimate estimation of the PCT for the most conservative thermal load of the cask. •The temperature distribution in a nuclear spent fuel has been obtained using CFX.•A mesh independency study has been carried out for the models.•A sensitivity regarding the flow modelling near the wall has been performed.•Enabling an anisotropic thermal conductivity can impact noticeably the results.