Thermal and ignition type steam explosions of single drops of molten aluminum

Interactions between drops of molten Al-Li alloys and liquid water

“…• Streams of bubbles of the sort observed here never relined when globules of pure aluminum with similar weights and at similar temperatures were released into liquid waterat room temperaturecontainedin a similar chamber (Nelson et al 1989(Nelson et al , 1991b(Nelson et al , 1990c • When underwatersteam bubbles with volumes as large as 1 L were formed intentionally by triggering steam explosions of these same pure aluminum globules in v,,ater at room temperature, the bubbles collapsed quickly and disappeared permanently, usually within about 20 msec, due to condensation (Nelson et al 1989(Nelson et al , 1990c. The rise times of the bubbles generatedby the AI-Li globules were long compared to these disappearancetimes (typically, it takes about400 msec for a bubble formed at the tx)ttom of our chamber to ri_e to t_e surfaceof the water).…”

“…This might be because of mechanical motion caused by the onset of transition boiling of water while the metal is still molten. Since aluminum and its "alloysfreeze at about the same temperature that transition boiling would _t in (Nelson et al 1991b), it might be expected that these alloys might not explode spontaneously if the melt were partially or completely solidified.…”

“…Although thereare studies of theexplosions that occurduringrelease of large amountsof these alloys intowaterand other coolants (Page et al 1987), accounts of industrialaccidents with the alloys (Epsteinand Miller1987), underwater capacitordischargefommfionandcombustionof tiny dropsproducedfroman AI-Lialloy wire (Lee and Ford1988), scoping studiesof the release of dropsof a commercial Al-Cu-Li alloy into water (Nelson et al 1989), relatedstudiesof the solubility (Anyalebechiet al 1988(Anyalebechiet al , 1989a(Anyalebechiet al , 1989b and diffusion (Anyalebechi 1990) of hydrogen in the liquid and solid alloys and their oxidation (Partridge 1990), there is no directly applicable information_ to "allowappropriate predictions. Moreover, because of the generation of gaseous hydrogen and nonprotective oxides as the alloy drops react with water, earlier studies of the interactionsof aluminumdropswith water(AndersonandArmstrong1981, Nelson et al 1991bNelson et al , 1990c) also offer littlepracticalguidance.…”

The Trigger Mechanism of Vapor Explosion

“…There are many experimental investigations about the trigger mechanism. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] It is pointed out that the vapor explosion is suppressed under the conditions of (1) low subcool of coolant, (2) uranium dioxide, (3) high pressure and (4) small amount of coolant on the containment vessel floor. However, it is not identified yet that the coolant subcooling and molten material properties affect and suppress which process of the vapor explosion, since the trigger mechanism is consist of many complex processes and it is very difficult to identify the dominant mechanism for each process.…”