# Why does the U.S. Army use "depleted uranium" to make munitions? **URL:** \ **Category:** Factual Questions\ **Created:** [May 5, 2003, 4:05pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206 "2003-05-05T16:05:08Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [May 6, 2003, 1:59am UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/21 "2003-05-06T01:59:35Z")
Any idea as to how these DU shells are machined ? or are they just casted ? ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [May 6, 2003, 5:29am UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/22 "2003-05-06T05:29:10Z")
Well, golly. For once I might get to add a worthwhile bit. One machines brittle metals at low speeds and low feed rates. I went and googled a couple of sites talking about machining tungsten. It sounded just like the chill around a malleable iron cast slug. Now, just FYI, a friend of mine machines tungsten on a regular basis so I’ll have to go pick his brain tomorrow, but I can tell you that brittle metal’s a relative bitch to machine (ain’t nothing like 12L14). (Plus you get black boogers in your nose from leaning over the work.) As a machinist I’d guess they make pretty tight casts, either investment casting or die casting (q.v.) so there is not a great deal of material to be taken off of the cast. As a machinable figure it is fairly regular. The penetrator is a long cylinder with tapered ends. The front needs to accept a ballistic cover of some sort (read aerodynamic and cheap) and the back gets fitted to a set of aluminum (or aluminium, as you will) fins. That’s about it, as far as I can figure out. They’re not doing a lot of machining on these bad boys. I’ll be back at 6:00 am PST to bump this up for our East Coast dopers. ---
**Author:** ![bugg](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@bugg](https://boards.straightdope.com/u/bugg)\ **Post date:** [May 6, 2003, 6:51am UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/23 "2003-05-06T06:51:31Z")
Regarding the 4.5 billion year halflife, when you have kilograms upon kilograms of it, you have decays happening at a rate that’s considerable. When you’re talking about the dust getting into your lungs, you have uranium particles that aren’t stable enough where they won’t decay at all before you die, but are rather decaying at such a slow rate where you’re constantly exposed to low level radiation (predominately in the form of alpha particles) - and the health data from what that can do to you is, well, inconclusive at best. If the halflife were shorter, it’d be far more dangerous but for less of a time. But there’s still evidence to suggest that U-238, at 4.5 billion years, is decaying rapidly enough to be a health risk but not rapidly enough to be able to wait it out. That’s the 4.5 billion year figure. BTW, I have had the honor of meeting Doug Rokke, who was in charge of cleaning up tanks destroyed by DU (friendly fire) in Saudi Arabia and Kuwait. He and his team are all sick or dead, and I tell you, he’s an interesting guy to talk to. ---
**Author:** ![Blackclaw](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@Blackclaw](https://boards.straightdope.com/u/Blackclaw)\ **Post date:** [May 6, 2003, 11:58am UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/24 "2003-05-06T11:58:14Z")
> [@](#): > > \*Originally posted by SenorBeef \* > \*\*Tungsten was actually used by all sides in Europe during WW2 for special enhanced penetrator rounds. I’d imagine the modern preference for DU, if it’s slightly basically inferior, would be due to it’s mass producability. \*\* Tungsten is an inferior penetrator. The Iraqis use tungsten ammo with little success against US tanks ---
**Author:** ![SCSimmons](https://avatars.discourse-cdn.com/v4/letter/s/e495f1/32.png) [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)\ **Post date:** [May 6, 2003, 2:08pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/25 "2003-05-06T14:08:50Z")
> [@](#): > > \*Originally posted by Marley23 \* > **Depleted uranium IS easier to come by: the material used is radioactive waste. Instead of being buried, it’s made into shell casings and used in various rounds and bombs. The name “depleted uranium” is actually a bit misleading, since it also contains plutonium and other elements.** This is incorrect. Depleted uranium rounds are _not_ made from radioactive waste-this misconception may be the source of some of the misunderstanding regarding these rounds. Natural uranium consists primarily of two isotopes: U-238 and U-235. Only U-235 is fissionable, and the concentration (a bit less than 1%) is insufficient to maintain a self-sustaining chain reaction. Early nuclear piles used external neutron sources to maintain fission, but to build a power plant or fission bomb, the proportion of U-235 must be increased to ~5% or ~90%, respectively. So, from 100 kilograms of natural uranium, you can make about 20 kg of power-plant grade uranium with 80 kg of virtually pure U-238 left over. Or, you can make about 1 kg of weapons-grade uranium with 99 kg of U-238 left over. As anyone who grew up during the Cold War can attest, the U.S. has made a hell of a lot of nuclear weapons, using a tremendous amount of weapons-grade uranium. That means they have about 100 times as much pure U-238, a.k.a. depleted uranium, left lying around. So it’s real cheap-effectively free, since we were going to be left with it anyway … ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [May 6, 2003, 2:24pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/26 "2003-05-06T14:24:06Z")
So SCSimmons, what about the phrase “the material used is radioactive waste” is incorrect? I read your explanation, but that seems to agree with the statement. I guess I can see that most people would assume that “radioactive waste” is what you take out of a reactor when it’s no longer useful for fuel, but I’d still consider the term to include what’s left over after you get enriched uranium, be that for a power plant or weapons. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [May 6, 2003, 2:34pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/27 "2003-05-06T14:34:25Z")
> [@](#): > > _bugg wrote:_ > If the halflife were shorter, it’d be far more dangerous but for less of a time. Well, if the half-life were 4.5 _thousand_ years, it would be one million times more dangerous for one-millionth of the time. However, 4500 years is still a whole lot longer than I’ll be exposed to it, so I would just say that it’s a million times more dangerous. ---
**Author:** ![Tony\_Montana](https://avatars.discourse-cdn.com/v4/letter/t/278dde/32.png) [@Tony\_Montana](https://boards.straightdope.com/u/Tony_Montana)\ **Post date:** [May 6, 2003, 2:49pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/28 "2003-05-06T14:49:08Z")
> [@](#): > > \*Originally posted by owlofcreamcheese \* > \*\*they use it because they have to, nothing else can take out thick armor effectively, and unless we want our people being shot by invincible tanks we need to use whatever there is that will stop them, if you can think of something better, I’m sure they will use it. \*\* But what of the[TOW missile ?](http://www.leyden.com/gulfwar/tow.html) IIRC there’s a more portable versions also. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [May 6, 2003, 2:51pm UTC](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206/29 "2003-05-06T14:51:35Z")
It was my mistake, and I actually semi-corrected it later. It’s not radioactive. It’s left over from nuclear reactions, but it’s not itself radioactive (won’t make you glow ;)). [Previous page](https://boards.straightdope.com/t/why-does-the-u-s-army-use-depleted-uranium-to-make-munitions/173206.md?page=1)