--- Ronn!Blankenship <[EMAIL PROTECTED]> wrote: > No. Naturally-occurring uranium is about 99.3% > U-238 (half-life 4.5 > billion years) and 0.7% U-235. Only the U-235 is > fissionable, so the two > isotopes must be separated for use in nuclear power > plants or nuclear > bombs. The left-over non-fissionable material (99.6 > to 99.7% U-238 IIRC, > as the separation process is not perfect) is what is > called "depleted > uranium" and used in places where a metal which is > significantly denser > than lead is desired, such as armor-piercing rounds > and as the > counterweights for the control surfaces on aircraft. > (From > <<http://www.science.co.il/PTelements.asp?s=Density>>, > the density of > uranium is 17.95 g/cm^3, and the density of lead is > 11.35 g/cm^3, so a > given volume of uranium has 1.58 times the mass of > the same volume of lead.) > > -- Ronn! :)
Hey Ronn. I believe that there's actually more to it than just that. DU is used in both armor and armor-piercing rounds. This isn't terribly surprising - so it steel, after all. It's useful in armor because it's very dense and very tough (osmium, for example, is denser than Uranium but also melts in your hand).
Um, just to be picky, osmium melts at 3045�C and boils at 5027�, so you must have a rather warmer hand than I do. You may be thinking of _gallium_, which has a melting point of about 30�C and so will melt in your hand. (As would cesium and francium, but both of them are alkali metals which would react rather violently with the moisture in your hand to release hydrogen energetically enough that it would catch on fire, and francium is radioactive besides.)
Osmium is indeed the densest element at 22.6 g/cm^3, though iridium is so nearly equal in density that it is very difficult to actually measure the difference in density between the two metals.
It's useful in projectiles for both those reasons, plus an interesting third one - DU has some neat mechanical properties. A round made of DU that impacts instead of deforming as it punches through the armor (the way steel would) actually flakes off in bits and pieces, and the flakes tend to ignite. Thus a DU sabot round that hits an enemy tank both smashes through the armor _and_ ignites the flammable objects (ammunition and people, chiefly) inside.
This is true.
I suspect that an additional practical reason why DU is used is the fact that a fair amount of it is produced as a waste product of the nuclear industry . . .
-- Ronn! :)
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