Thermal explosions resulting from fuel-coolant interactions: Analysis of single bubble hydrodynamics

Abstract: High-speed photographic data and pressure traces of thermal explosions from the contact of single drops of iron oxide with water were analyzed according to models describing underwater chemical explosion and cavitation bubbles. The objective of the study was to develop a simple method for analyzing the microscale hydrodynamics of fuel-coolant interactions (FCI). We have found that for a given external pressure and liquid density essentially all the features of the radial motion of the explosion bubble, including the total energy release, are uniquely determined by a single parameter—the bubble period. Nearly all of the heat transfer from fuel to coolant occurs during the 10⁻⁵ to 10⁻⁴ sec timespan of coolant vapor film collapse during which the fuel fragments. The observable features of the resulting explosion bubble are not significantly affected by the degree of heat transfer from vapor to coolant liquid and the bubble can be modeled as an empty cavity. The method developed during this study should facilitate investigations on FCI by simplifying the analyses of thermal explosion data. Further attention can be given to experiments on the effects of fuel parameters,e.g., surface tension and viscosity, on fragmentation, heat transfer, and explosive yield.