Aluminum-Water Explosions

Inadvertent contact of molten aluminum and water may lead to an event termed a thermal explosion. These incidents may produce little vapor, but they are accompanied by sharp, local shocks which are potentially damaging to personnel and equipment. Although not a major problem to aluminum producers, they do occur in casting plants, and it is important that preventative measures be enforced. The same general comments apply to other metal processing industries such as steel and copper. 

The lead in studying both the cause and prevention of molten metal-water thermal explosions has been taken by Alcoa. The Aluminum Association also sponsored several research programs both at Alcoa and at Battelle-Columbus. The Ai onne Natio Laboratory has carried out experiments with molten aluminum and water. 

The test programs which are summarized in detail in this section were usually not planned to test a causative mechanism. Rather, they were carried out to determine the effect of variables which were thought to be important in initiating the event. The results were normally reported only as explosions achieved or, conversely, not achieved. 

In most tests, molten aluminum was poured into a vessel containing water. In a few instances, however, water was injected onto or below a pool of aluminum. The first type of experiment would model one of the more familiar types of industrial accidents, i.e., one in which an ingot break or a furnace leak allowed molten aluminum to contact a source of 

The aluminum spill tests in water led to effective plant preventative schemes wherein organic coatings were placed on all solid surfaces which, in the event of an accident, might be in contact with molten metal and water. Use of such coatings has greatly diminished the frequency of thermal explosions. 

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Experimental test results for molten aluminum-water RPTs are described in Section V. Also shown is a tabulation of most documented aluminum-water explosive boiling incidents (see Table XIV). In many accidents, the quantity of water was quite small, e.g., some resulted when wet aluminum ingots were loaded into melting furnaces containing molten aluminum. In contrast, one notes that few, if any, serious events have ever been obtained when small quantities of aluminum were contacted with a large mass of water. Since laboratory tests were often carried out in the latter fashion, most of these have produced negative results. 

Besides the aluminum industry, the nuclear power industry has been interested in molten aluminum-water explosions due to the presence of aluminum metal in some boding water reactors. Certain accident scenarios lead to a meltdown of the reactor core with concomitant contact of molten aluminum and water. 

Results from extensive test programs on molten aluminum-water explosions have been reported by Long (1957), by Hess and Brondyke (1969), and by Hess et al. (1980). In almost all experiments, molten aluminum, usuaUy 23 kg, was dropped into water from a crucible with a bottom tap (see Fig. 9). In only a few tests was there instrumentation to indicate temperatures, pressures, delay times, etc. The test results were normally reported as nonexplosive or explosive—and if the latter, qualitative comments were provided on the severity of the event. A large number of parameters were varied, and several preventative schemes were tested. Over 1500 experiments were conducted. Some of the key results are summarized below. ... 

It is clear that the Alcoa research teams have provided a valuable data base to examine the mechanism of aluminum-water explosions. However, before considering proposed theories, the research studies at Argonne National Laboratory and elsewhere are summarized. 

Higgins quotes unpublished work at both Aerojet and DuPont that aluminum-water explosions were difficult to obtain, but alloys of aluminum with small amounts of lithium, sodium, or uranium were quite reactive. 

Extending this concept, we now consider those experiments which led to molten aluminum-water explosions without the presence of a wet, solid surface. In all of these there was an external shock applied to the system—usually in the form of an exploding wire or a detonator. As presumed by the investigators, these artificial shocks could be very effective in collapsing steam films. 

Dewing, E. W. (1980). The initiation of molten aluminum-water explosions. Memo., AIME Meet., 1980, Las Vegas, Nevada. 

As with the smelt-water case, if an RPT did take place, the event was localized and rarely was dam e severe far from the site of contact. Modeling molten aluminum-water incidents (and, in fact, other molten metal-water explosions such as in the steel industry) has not been partic-... 

Several studies attempted to determine whether chemical reactions were occurring at the aluminum-water interface. The finding that there was some light emission and local high temperatures led to the conclusion that reactions do occur, and they may be of more importance in the more violent explosions. 

In Table XV, some data are given for molten metal-water explosions not involving aluminum. In most of these cases, the quantity of metal was large. Because only the more serious explosions are reported, these tend to illustrate the most damaging type of event. Again, it is interesting to note that usually only small quantities of water were involved. 

Two large blocks of aluminum, each weighing about 600 kg, were being loaded into a furnace. Later investigation ascertained that one block had a small amount of water (about a teaspoonful )- When this block entered the molten aluminum, an explosion occurred... 

Anderson, R. P., and Armstrong, O. R. (1981). Experimental study of small scale explosions in an aluminum-water system. Pap., Winter Anna. Meet., ASME, 1981, New York. 

Krause, H. H., Simon, R., and Levy, A. (1973). Smelt-Water Explosions, Final reports to Fourdrinier Kraft Board Institute, Inc. Biittelle Laboratories, Columbus, Ohio. Lemmon, A. W. (1980). Explosions of molten aluminum and water. In Light Metals 1980 (E. McMinn, ed.), p. 817. (Proceedings of Technical Sessions Sponsored by TMS Light Metals Committee at 190tb AIME Armuat Meeting.)... 

Aluminum (or Magnesium)-MethanoI (or Water) Explosives. According to Shidlovskii (Ref l mixts of Al and HaO(2 3) or Mg and H20(1 1) are capable of combustion when subjected to intense heat. The Mg mixture can be detonated with a primer while the Al mixt cannot. The same investigator claimed (Ref 2) that on the basis of theoretical calcns of. he at evoln, mixt s of Mg or Al with HaO or ales are potentially more powerful expls that the usual military materials, with.Mg-MeOH giving the max gas evoln. The tests were conducted in bombs or lead enclosires with tetxyl detonarors to set off the mixts of powdered metal and the liquid. All mixts tested were found to be powerful expls with Mg-H30 being most sensitive to shock, while Al-HaO and Mg-MeOH were less sensitive and required a booster... 

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