Development of scaling laws of heat removal and CFD assessment in concrete cask air path

This study investigates heat transfer in a concrete cask such as one used at intermediate storage facilities of PWR spent fuels. Sufficient removal of decay heat is necessary not to damage fuel cladding that functions as a radioactive materials barrier. The experimental design parameters were derived in the half-scale model for the assessment of the design analysis methodology including a CFD tool. The scaling methodology was developed to design the half-scale model of the concrete cask in the spent fuel dry storage through scaling analysis. As one of the most important scaling laws, the requirement of similarity was selected for the temperature rise between the inlet and the exit in the air path. Based on the natural circulation in the channel, the scaling law was derived for total canister power maintaining the similarity of the temperature rise. Then, the temperature calculation and the flow analysis were performed in concrete cask facilities for the prototype and the half scale model using Computational Fluid Dynamics code. Through the CFD simulations, the similarity of the temperature rise was demonstrated well between the inlet and the exit, and the exit temperature was well maintained between the prototype and the half scale model. Also the scaling ratios of air mass flow rate and exit velocity obtained by the scaling analysis were in good agreement with those predicted by CFD analysis.