The only effective difference between explosive ejection and high pressure spray discharge is one of burning rate. Under given temperature conditions, the rate of reaction is a function which depends on the rate of sodium exposure, which in turn depends on the mass rate and particle size of the sodium discharge.

Experiments at Argonne National Laboratory (35) for explosive ejections of 400°F sodium in 3-10 msec have shown that the pressures produced are much less than theoretically possible (Fig. 4.29). It is clear that there are three zones of combustion:

(a) When only a small amount of sodium is present, the peroxide is formed an pressures are only moderate because the peroxide reaction has a lower heat release than the oxide reaction.

(b) When more sodium is present, more heat is produced as the oxide is produced, because the extra sodium reduces the peroxide.

(c) When even more sodium is present, it acts as a heat sink and it is very effective in reducing the overall pressure rise.

The rate of fallout of the reaction products is an important parameter in the pressure-time characteristic, since, in the experiments, over half the airborne reaction products had settled to the floor of the reaction vessel within one minute of the ejection.