Abstract
ABSTRACTStudies 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.
Highlights
In sodium cooled fast reactors (SFR), the leakages in the secondary sodium pipes lead to sodium fires, which are classified as Pool fire, Spray fires and Column fire
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
Several studies have been initiated in Aerosol Test Facility (ATF), Radiological Safety Division (RSD), Indira Gandhi Centre for Atomic Research (IGCAR) related to physical and chemical characterization of sodium aerosols which help in hazard evaluation of Sodium cooled Fast Reactors with respect to sodium fire and dispersion of sodium aerosols
Summary
In sodium cooled fast reactors (SFR), the leakages in the secondary sodium pipes lead to sodium fires, which are classified as Pool fire, Spray fires and Column fire. The size of the sodium aerosols, formed at given humidity condition and suspended in a confined environment, changes by (i) accumulation of water vapour over particle followed by chemical conversion (Sitarski, 2012) and (ii) coagulation by physical process. The initial conditions are taken as: the initial mass concentration c = co obtained from the experimental value (for two different concentrations) and initial particle size is taken from the empirical relation derived from the previous experimental results conducted in ATF, (Subramanian and Baskaran, 2007) in which Cooper’s relation (Cooper, 1980) is modified by taking an empirical constant as 0.97 and dry particle radius (r0) = 0.45 measured in ATF at RH% of 20. By taking initial sodium aerosol radius from the modified Cooper relation, the parameters λ, and K are calculated Using these values, equations are solved for time step and the process continued till the convergence of size is reached
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