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This is an old revision of this page, as edited by 178.15.151.163 (talk) at 15:52, 7 June 2016 (→‎Sanity check). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Sanity check

There is loads of talk here about uranium causing radiation related effects. For a quick sanity check Uranium-238 has a half life of 4.5 billion years - this is so long that the radioactivity is minute, certainly being exposed to U238 dust is radiologically irrelevant [ref I will do the sums if anyone asks]. It is a heavy metal and that causes chemical issues but anyone claiming radiological issues with U238 is either ill informed or a scaremonger. — Preceding unsigned comment added by Mtpaley (talk • contribs) 00:54, 26 August 2013 (UTC)[reply]

If you're talking about depleted uranium, you have yet to explain the fact that all kinds of birth defects and cancer swept through Falluja after depleted uranium bombs fell there. Coincidence? I think no — Preceding unsigned comment added by 99.124.143.83 (talk • contribs) 21:14, 1 February 2015‎

Mtpaley, you say "certainly being exposed to U238 dust is radiologically irrelevant [ref I will do the sums if anyone asks]". Ok, you're on. Let's see the math. It would be a good addition to the article. GangofOne (talk) 09:24, 18 February 2015 (UTC)[reply]
Let's try this analysis on for size. Herein I use e notation: 3e-2 is the scientific 3x10-2, or 0.03.
Typical fallout dust particles (http://www.engineeringtoolbox.com/particle-sizes-d_934.html) range a factor of ten on each side of a micron in size. Uranium metal density is about 20 gm/cm^3, so the average mass of a 100% uranium particle is 20 / (e-6)^3 = 2e-17 grams. 238 grams of U-238 contains 6.02e23 uranium atoms (Avogadro's law). So a typical fallout particle contains about 5 million uranium atoms, assuming the particle is 100% uranium, plus or minus a factor of 10. [Oops, make that a thousand, 10^3.]
Now, the half-life of U-238 is, as stated, about the age of the Earth, about 4.5e9 years. Roughly stated then, it takes about 4.5e9/5e6, or about a thousand years on average for a single uranium atom in that particle to decay, throwing off an alpha particle and an atom of Th-234. It is well known that thermal alpha particles (typical of decay alphas) pose little threat to humans externally; they are absorbed by dead exterior skin cells with zero detrimental effect. Internally, they may impinge on live cells, and in sufficient concentration, "burn" close cells. One alpha per 1000 years means that over an average human lifetime, uranium particles, unless present in truly huge numbers, are inert.
Why do people worry about fallout, then? Because it holds many substances which have much shorter half-lives than U-238. Iodine-131, for example, with a half-life of 8 days. In DU penetrators, uranium-238 is the only radioactive material present. This is a totally new concept for many anti-nuke people, that the isotopes to worry over are those with the short half-lives, not those with the long ones. Well water in Finland, for comparison, shows 220 becquerels of radioactivity per liter from dissolved radon, and is considered safe (a becquerel is one decay event per second; the hypothetical U-238 particle gives off 3e-11 Bq).
I disagree that this analysis should be in the article - for one, it is original research (I've not seen this calculation anywhere else), which in wikipedia is forbidden. Second, it is very rough and there are lots of simplifying assumptions - the +/- 10x multiplier, for one, "cubic" particles, and what happens with the left-over thorium, for others. So I will leave it right here. Anyone is welcome to use it elsewhere with my full permission. SkoreKeep (talk) 04:26, 9 May 2015 (UTC)[reply]
The conclusions of mtpaley are consistent with what is stated (in Swedish) by the Radiation and Nuclear Safety Authority Finland. BP OMowe (talk) 19:00, 22 May 2015 (UTC)[reply]
Oy, where to start. Good thing we don't do original research; this is a mess! First off, a 1e-6 m cube (1 micron cube) of U-238 would weigh 2e7 g/m^3 * (1e-6 m)^3 = 2e-11 g. You were off by six orders of magnitude due to your units error. Assuming the nonconservative activity in a 1 micron cube when dust likely to be retained in the lung (not, of course, fallout) tops out at 10 microns introduces another 3 orders of magnitude error. For a range of 1-10 micron cubes, we have 5e10 to 5e13 atoms, not 5e6 (you made a 2 order of magnitude calculation error in this step somehow, but it partially cancelled out your earlier errors). For the activity level you want to use mean lifetime; not half life. The mean lifetime of 238U is 2e17 seconds, so that is 4e6 to 4e3 seconds (1-1000 hours) per disintegration per particle. A person exposed to a uranium fire could inhale many thousands of the particles.
Subsequent decay of 234Th and 234Pa daughter and granddaughter products happens instantaneously relative to the 238U half life, so the activity of the Uranium is effectively tripled to by the beta emitters. Summing up, the resulting activity is on the order of 0.01-10 Bq (a third of which will be the more damaging alphas). Hardly Chernobyl, but not the "one disintegration per 1000 years" you came up with either. Our article is accurate in reporting that the radiological hazard is negligible compared with the heavy-metal toxicity. VQuakr (talk) 05:27, 4 November 2015 (UTC)[reply]
And you can multiply all of those numbers by the number of particles inhaled, which is very unlikely to be one isn't it. It could in fact be an ungodly large number. 178.15.151.163 (talk) 15:52, 7 June 2016 (UTC)[reply]

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Erroneous unreferenced sentence

@ In Intro: "It is only weakly radioactive because of its long radioactive half-life (4.468 billion years for uranium-238, 700 million years for uranium-235; or 1 part per million every 6446 and 1010 years, respectively)." The strength of radioactivity of a radioactive substance is in no way related to its radioactive half-life. I do not know what point the writer was shooting at here, but it's a clean miss. Marbux (talk) 05:28, 22 October 2015 (UTC)[reply]

@Marbux: half-life and decay energy are indeed related for alpha emitters; see the Geiger–Nuttall law. I agree a source should be added, though. VQuakr (talk) 07:52, 22 October 2015 (UTC)[reply]

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