Comment by trhway | Hacker News Reader

Comment by trhway | Hacker News Reader

>Because, as the people of Kuwait discovered after first Gulf War, depleted uranium leaves a potentially deadly dust behind after it burns. It sounds bizarre but, in the world of warfare, tungsten is the eco-friendly alternative.

i knew it is bad, just googled and according to some sources it is really bad, especially when it comes to birth defects : http://www.huffingtonpost.com/craig-considine/us-depleted-ur...

It is not necessary radioactivity that makes DU that bad, it is its toxicity that does it. Unfortunately, DU is still better for armor penetration : https://www.theguardian.com/world/2000/may/18/armstrade.koso...

"Armour penetration is increased by concentrating the force of a shell into as small an area as possible, so the projectiles tend to look like giant darts. [ ... ] The other metal used for anti-tank rounds is tungsten, which is also very hard and dense. When a tungsten rod strikes armour, it deforms and mushrooms, making it progressively blunter. Uranium is "pyrophoric": at the point of impact it burns away into vapour, so the projectile stays sharp. "

For penetrators you want density, hardness, and other penetration aiding properties. Tungsten is very dense, but as you point out it blunts when hitting a target, reducing its effectiveness (but if you have enough it'll still work).

The guardian article you linked is a little bit off on the properties of Uranium. Uranium is self sharpening (which means that when it slams into a target it fragments splinters off, leaving behind a sharp point). Uranium is also pyrophoric, which doesn't mean that it burns away pieces into vapor, rather it means that when it scrapes along as it's penetrating through metal it throws off sparks, just as flint and steel does. Additionally, Uranium is more flammable than Tunsten. This means that a long rod Uranium penetrator can punch through thicker armor than Tungsten and it spits out a rain of sparks and splinters as a burning hypervelocity rod comes through the other side of the armor. This leads to a very bad day for the target.

However, because of that pyrophoricity and that burning the result of using lots of DU shells on hardened armored targets is a lot of DU dust and vapor. Because Uranium is a toxic heavy metal this can have disastrous health effects.

> However, because of that pyrophoricity and that burning the result of using lots of DU shells on hardened armored targets is a lot of DU dust and vapor. Because Uranium is a toxic heavy metal this can have disastrous health effects.

Well, I imagine being hit by a tank round has so profoundly disastrous health effects anyway, the metal toxicity doesn't matter much!

(Yes, I know you probably meant adverse health effects for the people who wander into the area after the crew is killed, much like it happens with nukes, but still. The considerations are bizarre, like the article said)

> Well, I imagine being hit by a tank round has so profoundly disastrous health effects anyway, the metal toxicity doesn't matter much!

It's also toxic for the people firing the rounds because blowing up a cartrigde will also evaporate some trace amount of the bullet.

The considerations are hardly bizarre.

People live in warzones. People live in warzones just after they've been warzones. This is even more true in urban warfare. This is why the civilized world tries very hard to avoid using landmines in war, and why there's so much effort into preventing civilian casualties with unexploded munitions like cluster bombs, for example.

There is an argument to be made on whether or not the risk of collateral damage is justified, it's impossible to make war completely "safe", of course, but with DU the evidence is stacking up that the collateral damage is extreme and probably not a good tradeoff.

The misconceptions about DU in the media always irritate me. People hear "Uranium" and immediately start talking about radioactivity, but the D in DU should remind them that the whole point of DU is that it's significantly less radioactive than naturally occurring Uranium. I can find more radioactive rocks lying on the ground only a few hours drive from where I live.

DU, considered as a radioactive substance, has low radioactivity and low biological half-life. From that narrow point of view, it's really quite innocuous.

Uranium is, however, a reactive heavy metal, and breathing those as dust has never been good for you, whatever the metal (as those downwind of industrial plants with poor environmental oversight will be happy to tell you.)

1) "the whole point of DU is that it's significantly less radioactive than naturally occurring Uranium"

The D in Depleted (U-238) has nothing to do with it's radioactivity but that it's not fissile. Fissile U-235 is not too badly radioactive either (4 billion vs. 0.7 million year half life i.e. 77% more radioactive 0.5^(0.7/4) / 0.5).

We don't make depleted uranium to have less radioactive uranium (naturally occurring uranium is < 1% U-235). We have DU because we made nuclear bombs.

Interestingly the Ruskies have made DU arms far more expensive now with their breeder reactor (U-238 is fertile).

2) DU is an alpha emitter. I would bath in a bathtub made of alpha-emitters and sleep in a bed of alpha-emitters.

However, Uranium shatters making dust. I would not want to breath, eat, drink an alpha-emitter. It's a heavy hitting He ion that will knock the socks off anything in it's short path.

Not to mention U-238 becomes Th-234 with a half life of 24 days (very radioactive) with beta emission (ouchy!). There'll never be a lot of Th-234 (U-238's low radioactivity) but it'll all decay into you (Th-234 small nuclear half-life and large biological one).

So U-238 effectively decays in your body as a an alpha and beta!

What happens when you blow up DU? Gets scattered throughout the local environment.

3) ...Low biological half life

That's only relevant for disaster tourists. For people whose environment has been seeded with the stuff, the biological half life is completely irrelevant as it is replenished as you eat, breath and drink. An equilibrium concentration is therefore established.

Therefore, environmental half-life is far more important than a biological one.

I'm not advocating DU as a part of a healthy diet. It's more than 100 times as radioactive as bananas, after all. I am saying that the primary danger from DU is not its radioactivity, but the fact that it's a heavy metal. That still true (possibly even more true) in an area with excessive DU contamination.

The fissibility of Uranium isotopes is critically important in weapon design and storage. With regard to biological danger, it's the radioactivity that is important (unless you happen to be near a prompt critical event, of course). DU is about half as radioactive as natural Uranium, so I think my "significantly" was justified.

Body burden and biological half-life are better indicators of a given radioactive substance's danger to living creatures, especially in the case of alpha emitters. That's why proactive measures like prophylactic iodine and showers are effective in contaminated areas. Of course accumulating more doses of an agent is always going to be more dangerous---what's important in comparisons is how dangerous one dose is.

Your Th-234 argument is misleading, and you know it. Yes it's nasty, but U-238 decays to Th-234 with a half-life of 4 billion years. That event would occur in a human body so rarely as to be completely immeasurable unless the human was contaminated with so much U-238 they'd die instantly from the toxic exposure and whatever horrific event deposited that much.

We ingest alpha-emitters with every meal, and while we should avoid ingesting more than we have to, at the small rates we do even in the presence of U-238 (or a diet rich in Bananas and Brazil Nuts, for that matter), there's no statistical impact on lifespan.

Reply on news.ycombinator.com