A CASTOR cask must safely remove the decay heat generated by spent nuclear fuel while maintaining the required shielding and containment functions. Because the cask is passive, heat transfer to the surroundings takes place without a conventional active cooling system.
FlowMotion used CFD and thermal analysis to determine the temperature distribution and heat dissipation from the cask. Heat is conducted through the solid cask structure and transferred from the outer surface to the surrounding air by natural convection.
Thermal radiation also contributes to heat rejection and becomes increasingly important as surface temperatures rise. The surrounding airflow is driven by buoyancy: air heated by the cask becomes less dense, rises and is replaced by cooler ambient air.
The coupled calculation provided local air velocities, temperatures and heat fluxes and made it possible to determine the resulting component and surface temperatures.
This approach allowed the passive thermal performance of the storage concept to be assessed under the relevant operating conditions.
