The safe and efficient storage of spent nuclear fuel is a crucial aspect of nuclear energy management. This study employs computational fluid dynamics (CFD) simulations to investigate the thermal performance of a dry spent fuel storage system under different ventilation conditions. The system comprises vertical wells housing fuel canisters, with cooling facilitated by either forced ventilation or natural convection. The simulations examine airflow patterns, temperature distribution, and heat transfer mechanisms in both ventilation modes. Results show that forced ventilation promotes a uniform velocity distribution, effectively reducing temperature buildup within the storage well. In contrast, natural convection relies on buoyancy-driven airflow, resulting in irregular velocity patterns and higher temperature gradients. Despite these differences, the maximum temperatures of the fuel canisters and concrete walls remained within safe limits (below 300 °C and 90 °C, respectively) under all conditions. These findings demonstrate that the ventilation system successfully regulates temperature, ensuring the safe and reliable long-term storage of spent nuclear fuel.