Suppression of Vapor Explosions in a Water-Molten-Tin System by Augmentation of the Void Fraction

Abstract

Experiments were performed to determine the likelihood of a vapor explosion when injecting an inert gas (nitrogen) and a coolant (water) into a pool of molten metal (tin) in a large-scale chamber (~20 kg fuel). The injection flow rates of the water and nitrogen gas were the principal experimental variables, with average water flow rates up to 0.05 × 10-3 m3/s and gas flow rates ranging from 0.33 × 10-3 to 1.67 × 10-3 m3/s. Of 35 successful experiments, 11 resulted in an explosive interaction, as determined by audible signals, videotape, and accelerometer data. The main objective of the investigation was to determine the existence of a boundary between explosive and nonexplosive regions in the water-gas flow rate plane: Such a boundary was indeed identified and approximated by a straight line. Two experiments in which explosive interactions were obtained in the low water/gas flow regions after a relatively long time of coolant injection (~5 to 10 s) demonstrate the hitherto undervalued importance of the temporal variable.