Impact of a high temperature sodium spray on a target: PDA preliminary characterization

The behaviour of high temperature sodium when spread into air is not well known, although of capital interest in preparing safety systems in plants that use large amounts of it. A new set-up was built to produce high temperature liquid sodium sprays and jets, that were observed when produced in nitrogen inert atmosphere and in air. Sodium sprays were produced by submillimetric nozzles simulating a small leakage, while a rupture diaphragm of 30 millimetres diameter simulated a more severe failure. Sodium was pressurised up to 9 bar, and heated up to 550°C, while the surrounding gas, nitrogen or air, was kept at atmospheric conditions. High speed cinematography was used to observe the liquid macroscopic behaviours, while Phase Doppler Interpherometry was used to measure the sodium droplets velocity and size, when possible. Particular care was put in preparing this new experimental set-up, because of the partially unknown and potentially dangerous phenomena involved, requiring double confinement of the spray set-up and remote controlled operations. Spray macroscopic shape and some granulometric characteristics could be measured, and are reported together with occurrence of ignition.