Experimental and numerical assessment of sodium aerosol behaviour during pool fire in a rectangular chamber

Understanding the spatio-temporal transport of the aerosol resulting from a sodium fire is essential for mechanistic assessment of the severe accident source term. To develop mechanistic models for evaluating aerosol transport, the Indira Gandhi Center for Atomic Research (IGCAR) has started a series of experiments to understand the spatio-temporal behaviour of the aerosol in a large volume. These experiments involved the measurement of the temperature, humidity and aerosol characteristics at multiple locations, which improved the understanding of aerosol spatial dispersion during typical sodium fires. In the first experiment, a pool fire was created using 2 kg of sodium in the MINA test chamber to obtain the spatial dispersion of the aerosol over time along with the temperature distribution. Before attempting a detailed mechanistic assessment of aerosol transport, lumped codes were developed in-house to assess the sodium pool, average gas and wall temperatures, pressures, and aerosol characteristics. Results from the experiment indicate spatial heterogeneity in the aerosol concentration across different elevations of the MINA test chamber, and there is a need for CFD-based assessment. The lumped analysis agrees well with the average temperatures, median diameters, and mass concentration. The maximum concentration of sodium aerosols in the chamber is approximately $\sim$ 3.2g/m${}^3$. The median diameter of the initial aerosol increases from $0.2\mu m$ to $5.5\mu m$ after 50 min of sodium fire. The median diameter of the aerosol decreases to $3\mu m$ after 180 min of the sodium fire. The details of the experiments and significant findings are discussed in the present manuscript.