The secondary effects of high-altitude nuclear explosions, such as neutrons, gamma rays, X-rays, and charged particles transported in the atmosphere, can cause radiation damage to important facilities and personnel such as airports. The Monte Carlo (MC) method can simulate the interaction between particles and matter, as well as the coupled transport of multiple particles in forming the nuclear radiation field, making it the most commonly used technique for the numerical simulation of nuclear explosion radiation environments. However, directly using MC program codes to model spatially complex three-dimensional geometries in large and intricate scenarios is a time-consuming and challenging task.

To address this bottleneck issue, this study investigates the modeling technique of converting large facility computer-aided design (CAD) geometric models into MC-computable codes. The method of combining CAD parametric modeling with MC computational models is applied for the first time. Additionally, a calculable MC code was constructed using the McCad conversion interface.

Finally, taking an airport as an example, a modeling of the airport control tower was conducted, incorporating parameters such as materials and structures, and a simulation of neutron radiation shielding was performed. This validated the feasibility of the proposed method and the constructed model, laying a foundation for further in-depth research on airport radiation protection.