Session: 11-02 Severe accident mitigation phenomena

Paper Number: 135227

135227 - Experimental Study on the Influence of Spray Characteristics and Temperature Control on the Removal Efficiency of Iodine Aerosols 

Abstract: 

Radioactive aerosol may be released into the gas and retained in the containment under severe nuclear accidents conditions. Spray system removal is one of the main ways to remove aerosols. Spray droplets and overpressure of primary loop in severe accidents create a complicated high temperature and high humidity environment. A significant portion of radioactive aerosols in nuclear accidents are soluble. These soluble radioactive aerosols (CsOH/CsI) in the containment of the high humidity environment will occur significant hygroscopic growth behavior and may dissolve in droplets. Moreover, if the spray solution is alkaline, changes in particle density, size, shape, and chemical composition of iodine aerosols may occur, significantly influencing the dynamic behavior of aerosol agglomeration, diffusion and deposition, and consequently, the aerosol removal efficiency of the spray system. While extensive research has been conducted on the spray removal of insoluble aerosols（TiO2\SiC）, studies on typical soluble iodine aerosols spray removal experiments are largely lacking. Mastering the spray droplet characteristics of the spray system and the thermal parameters of the environment is of great significance for the analysis of the removal efficiency of soluble iodine aerosols after nuclear accidents and the efficient control of the spray system.

In this paper, the experimental study of single nozzle with different spray characteristics on the removal efficiency of iodine aerosol was carried out. This study provides insights into the effects of different spray angles, pressures, flow rates, and pH values on the removal efficiency and influencing patterns of soluble iodine aerosols under various initial particle sizes, gas phase temperatures, and relative humidity conditions. Results indicate that, under similar aerosol density conditions, the aerosol removal rate were 7.9 × 10^-4s^-1 for iodine aerosols and 3.8 × 10^-4 s^-1 for TiO₂, soluble aerosols are more easily removed by spray systems in high-temperature, high-humidity environments compared to insoluble aerosols. The greater the aerosol solubility, the significantly higher the aerosol scavenging efficiency. The elevation of initial gas phase temperature and an increase in steam fraction exert a promoting influence on the spray removal rate of soluble aerosols. In the initial spray phase, soluble aerosol particles rapidly increase in size due to a substantial difference in water vapor pressure between aerosol surfaces and the spraying area. However, as spraying progresses into the middle and later stages, aerosol particle surface pressure equilibrates with external water vapor pressure. Concurrently, the droplet spraying action leads to a gradual reduction in aerosol particle size.

This study can provide reference for fundamental understanding of the aerosol removal mechanism of soluble iodine aerosols by containment spray droplets and improving the containment spray removal models.

Presenting Author: Jiaxuan Tang Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University

Presenting Author Biography: I am Jiaxuan Tang, born in 1995 in Yongchuan District, Chongqing. I am currently a doctoral candidate at Chongqing University, specializing in nuclear reactor thermal-hydraulics. During my master's, I focused on the numerical simulation of thermal-hydraulics in sodium-cooled fast reactors. In my current doctoral research, I am exploring the removal of radioactive aerosols. With a solid foundation in energy and power engineering, I am dedicated to advancing nuclear science for enhanced safety and efficiency.

Authors:

Jiaxuan Tang Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University
Yang Yang Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University
Luteng Zhang Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University
Jialong Li Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University
Liangming Pan Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University
Zhuo Liu China Nuclear Power Engineering Co., Ltd., Beijing 100840, China
Li Gao China Nuclear Power Engineering Co., Ltd., Beijing 100840, China
Yidan Yuan China Nuclear Power Engineering Co., Ltd., Beijing 100840, China