Performance Test and Simulation Study on the Air Path of CAP1400 Passive Containment Cooling System
Authors: Xinxin Pan , Jingyu Huang , Chunjing Song 
Published: October 2017

As a large scale passive pressurized water reactor nuclear power plant, CAP1400 can remove the reactor decay heat to outside containment with the air cooling in the air flow path of passive containment cooling system (PCS) during the long-term period following an accident. Flow resistance characteristic and wind neutrality characteristic are the main performances of PCS air flow path. In order to study the performance of PCS air flow path, it is necessary to carry out the PCS wind tunnel test and computational fluid dynamics (CFD) analysis to establish a suitable method for the analysis of the performance of the air flow path.
This paper comes up simulating the internal pressure and velocity distribution in the air flow path under different wind speed through CAP1400 PCS 1:100 scaled air flow path wind tunnel test to research the air flow resistance and internal flow pattern. The test shows that local uneven flow phenomenon exists in the outer annulus of the air flow path, but the wind pressure distribution of inner annulus is not affected by environment wind speed, wind direction angle, landforms and the surrounding buildings. The wind pressure is uniform at different heights on the cross section and shows the neutrality feature.
Combining with CAP1400 PCS wind tunnel test, the CFD model is built. The measured inlet wind speed, turbulent kinetic energy and turbulent dissipation rate distribution parameters are inputs and the uniform wind conditions and gradient wind conditions of simulation analysis are developed. Simulation results show that:
1) In uniform wind condition, simulation result of pressure coefficient distribution trend at each cross section is consistent with the test trend and the deviation is very small, which basically can be controlled below 5%. The simulated differential pressures between inner annulus and outer annulus at different elevation are basically identical with the test results, which increase as the elevation arises. The simulated velocity distribution is basically identical with the test. The wind velocity at the upwind and central area of the flow path outlet is larger than other area, and a large swirling region comes on the leeward side near the wall 15cm, but simulated swirling region size at leeward side is slightly smaller.
2) In gradient wind condition, the pressure coefficient distribution trends are basically identical, and the deviation between the test and CFD analysis is 5–10% approximately. Considering the stability of gradient wind condition in wind tunnel is worse than that of uniform wind conditions, and more prone to wind speed fluctuations, therefore, the deviation is slightly greater than the uniform wind condition.
According to the CFD simulation and wind tunnel test, it can be found that the simulation of air flow inside and outside annulus has a high precision though the test results are slightly affected by the instrument tubes along the two sides of test model. In general, CFD simulation and wind tunnel test results are basically identical. Therefore, CFD analysis method is well verified by PCS wind tunnel test, which can be applied to the analysis of the actual power plant.