Numerical Simulation of Air Flow through Cracks of Structures in Nuclear Power Plant

Objective Human health is protected by nuclear plant ventilation systems providing the dynamic air shields by maintaining differential pressure between contamination zone and other areas and the radioactive contamination leaking is prevented. Under the premise of the shielding function for radioactive materials, it is important to avoid excessive design redundancy in fan flow capacity, thereby enhancing the economic viability of nuclear power plants.

Method A numerical simulation study was conducted by the domestic computational fluid dynamics software KILI V1.0 to simulate the air flow experiments within building gaps completed by Baker et al. The results were compared with those obtained by commercial software FLUENT.

Result The critical Reynolds number within narrow gaps could be very low, potentially leading to turbulent flow conditions even at low air velocities. Therefore, turbulence models should be adopted in three-dimensional simulation. The method of determining the boundary layer mesh thickness based on the Y+ value did not achieved good computational results. Instead, the approach of using a fixed boundary layer mesh thickness yields better accuracy.

Conclusion The KILI software demonstrated high accuracy in calculating air flow within narrow gaps. During the design process of ventilation systems, numerical simulation methods can be employed to reasonably match the designed ventilation rate of the room with the ventilation rate through door and window gaps. This approach allows for avoiding excessively redundant designs while ensuring the shielding function for radioactive materials, thereby balancing the safety and economy of nuclear power plants.