Analysis of Deformation Effects on Falling Spray Droplet Motion Under Postulated Sodium Spray Fire Scenario in SFR

Analysis of accidental sodium leak resultant fire events is important in the safety evaluation of Sodium-cooled Fast Reactor (SFR). The sodium leaked out from the heat transport system can disintegrate into numerous droplets of various sizes and their burning in the surrounding air atmosphere constitutes the spray fire event. Accurate evaluation of droplet velocity is essential in the spray fire analysis, as the residence time and burning rate of spray droplets in the air depends on the falling velocity. In this work, a numerical model has been developed to evaluate the falling sodium droplet motion in the gas medium along with the possible droplet deformation effects. The model has been validated using the settling velocity data of free falling liquid droplet experiments in the literature and model predictions shown good agreement with the experimental results. The model has been used to evaluate the settling velocity of sodium droplets of different sizes and these results revealed the effect of droplet deformation on the falling velocity of sodium droplets. This model is incorporated into the sodium fire analysis code for the realistic simulation of postulated sodium spray fire events in the safety evaluation of SFR.