Full-Load Thermal–Hydraulic Optimization of Spent Nuclear Fuel Storage Vaults

The increasing use of nuclear energy, a reliable baseload power with minimal greenhouse gas emissions, makes managing the heat of dry storage for spent nuclear fuel (SNF) a key engineering issue. Our research indicates that strong heat layers form in standard setups, with over 40% of the vault exceeding 85 °C when airflow stops. A staggered cask setup with outlets on both sides and a 0° inlet yielded the best results, exhibiting the lowest standardized temperature (θave = 0.23) and maintaining wall temperatures below 65 °C. Input speed (4.0–6.0 m/s) is the most significant factor, dropping output temperature from 80 °C to 38 °C. While convection is the primary method of heat transfer (over 90%), radiation becomes significant in low-flow areas, although its effect diminishes as surface temperatures increase. Pressure loss stays low (about 3.2 Pa), which is suitable for mechanics. To improve the system’s practicality and sustainability, it is advised to use both active and passive cooling and to reuse low-grade heat. This work provides reliable guidance for HVAC design under full-load conditions, enhancing the safety, energy efficiency, and cost-effectiveness of SNF storage.