Research on the performance of a passive cooling system for main control room emergency habitability

During severe accidents in nuclear power plants, the Main Control Room (MCR) Emergency Habitability System (VES) maintains a suitable thermal environment for operators and equipment to prevent accident escalation. However, existing VESs often fail to provide sufficient cooling capacity for the required 72-hour period. Considering the complexity and importance of the VES, this study integrates passive components to establish a passive cooling system that enhances cooling performance with minimal structural modification. Experimental and numerical analyses are conducted to evaluate the effects of operational and structural parameters on system cooling capacity and to determine the optimal configuration. Results indicate that the active chilled beam (ACB) contributes over 70% of the total cooling capacity, while the vortex tube accounts for less than 30%. Increasing the ACB entrainment ratio is an effective approach to enhance system performance, and the ejector works synergistically with the ACB to promote temperature reduction. Raising the initial room temperature is more effective in increasing total cooling output than reducing water temperature or increasing water flow rate, primarily because short-circuiting airflow occurs around the ACB, leading to poor indoor air circulation. To address this, the ACB should be installed flush with the ceiling, and a 30° supply angle under the vertical supply mode provides the optimal setup. Moreover, excessively high supply water temperature, low water flow rate, or insufficient compressed air pressure significantly reduces cooling performance. The findings offer a low-intervention and adaptable method to improve the emergency habitability of the VES.