Volume 15, No. 6, November 2015, Pages 2270-2276 PDF(697 KB)
Size Evolution of Sodium Combustion Aerosol with Various RH%
Amit Kumar, Venkatesan Subramanian, Ramakrishnan Baskaran, Balasubramanian Venkatraman
Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, India
- The initial size distribution of sodium combustion aerosol is independent of mass concentration.
- The size of aerosol increases by absorption of moisture.
- Hygroscopic growth particle size is dominant in the mass concentration of about 0.5 g m–3.
- Coagulation growth particle size is dominant in the mass concentration of about 3.0 g m–3.
- Higher the RH%, the particle enlargement is also found higher.
Studies on sodium aerosol characteristics are very important for fast reactor safety. Physical and chemical changes that occur at various times at various atmospheric conditions to sodium aerosols would results particles in various diameters. In this context, a study has been conducted in Aerosol Test Facility, Radiological Safety Division, in which sodium combustion aerosols were generated in a controlled manner and made to hover in a confined volume. The particle diameter (Mass Median Diameter - MMD) is measured on-line with progress of time by using Mastersizer. The experiments are conducted by generating aerosols in two different mass concentrations viz. 3.0 g m–3 and 0.5 g m–3 and in three different relative humidity conditions viz. 20%, 50% and 90% to show the influence of relative humidity on the particle diameter. A theoretical simulation of particle growth due to coagulation is drawn and compared with the experimental value. It is observed that sodium combustion aerosols size grow due to absorption of moisture (hygroscopic growth) in the initial period of times say in first 20 minutes followed by Brownian coagulation. An empirical relation is determined based on the difference between coagulation growth and experimental observation and applied to match experimental observation of particle diameter. A detailed experimental procedure, theoretical simulation and comparison of results of particle growth between experimental observation and theoretical simulation are presented in this paper.
Sodium combustion; Aerosol size; Growth; Relative humidity.