Numerical analysis of forced convection heat transfer in a nuclear fuel storage vault

Forced convection heat transfer from fuel and blanket subassemblies to air in a nuclear fuel storage vault has been investigated in this work. Three dimensional simulations were performed for an actual fuel storage vault to improve the decay heat removal, air exchange rate, and thermal effectiveness. Forced airflow was used to remove the decay heat and an efficient ventilation arrangement was rigorously studied for long term storage of the nuclear fuel. The height of the interconnecting ducts between the blanket and fuel storage enclosures was systematically investigated to understand the ventilation performance. For this purpose, different temperature and air distributions inside the vault were analyzed. The mixing of air was enhanced, and the thermal stratification was reduced by connecting the ducts above the heat generating region. However, the fuel magazine temperature was reduced when the ducts were connected below the heat generating region. Furthermore, the effect of different shapes of interconnecting ducts on heat removal and air exchange rate through the vault was investigated. It was found that incorporating nozzles in the interconnecting ducts has led to an enhancement in air jet penetration and consequently a reduction in hot spot temperature. The validated computational model will be helpful in designing different aspects of nuclear fuel storage systems.