[ RadSafe ] uranium fire fume characteristics

[James Salsman]

Bill Kolb wrote:

> There's too much theoretical chemistry and not enough real chemistry in
> this discussion.

You are absolutely right about that.  The empirical fact is that
B. Salbu et al. found uranyl ion in the combustion product of an
enclosed burn -- something that U.S. Army scientists have apparently
never thought to try, or to look for:
   http://dx.doi.org/10.1016/j.jenvrad.2004.04.001

Quoting Simon Cotton in _Lanthanides and Actinides_ (New York:
Oxford University Press, 1991) page 126:  "Aerial oxidation of
any uranium compound eventually results in the formation of a
uranyl compound."  See also:  S. P. McGlynn and J. K. Smith,
J. Mol. Spectrosc. 6 (1961) 164; R. G. Denning, et al., Mol. Phys.,
37 (1979) 1109; W. R. Wadt, J. Amer. Chem. Soc., 103 (1981) 6053;
P. Pyykko et al., Inorg. Chem., 28 (1989) 1801.

The culprit could also be UO3, a light oxide (uranyl oxide?!) that
the U.S. Army has also apparently never found, probably because of
their open-air burning methods.  UO3 is only slightly less soluble
than U3O8, and represents about a fifth of typical combustion
products by weight of the original uranium, but it's much lower
density apparently causes it to waft up and out of range of collectors
placed near the base of the fire, where UO2 and U3O8 accumulate.

Quoting A. Pfister in Chapter 8, "The Chemical Toxicity of Uranium,"
of _Depleted Uranium: Sources, Exposure and Health Effects_ (World
Health Organization, Ionizing Radiation Unit, 2001 --
http://www.who.int/ionizing_radiation/pub_meet/en/Depluranium4.pdf ),
page 103: "Until more information on the chemical form of uranium and
DU in the environment is obtained, it would be prudent to assume that
it is in a soluble form (ICRP Type F)."

> UO2(NO3)2 completely decomposes into an oxide when
> heated above a few hundred degrees C (about 500C, if memory serves but
> definitely at liquid soldering temperatures). It goes from a light
> yellow-green color to a deep orange just before decomposing into the
> oxide.

That is correct, too, except perhaps one could quibble about the word
"completely."  Sadly, a few milligrams of aerosol uranyl compounds can
be more toxic than several grams of UO2 or U3O8.  Something is causing
a 50% increase in birth defects in children fathered by 1991 Gulf war
veterans, and there are no remaining hypotheses that don't involve
uranium.  Oil well fire smoke, anti-nerve gas agents, insect repellents,
etc., have all been ruled out by noncombatant cohort studies.

> At the temperatures it would take to form UO2(NO3)2 in the first
> place, I find it very difficult to believe anything but the oxide
> would survive.

Fair enough.  The characteristics of a uranium fire involves rapid
cooling as pressure forces products out from the plasma into the
surrounding air.

Sincerely,
James Salsman

P.S.  I have recently learned that the U.S. Defense Department does
not have any valid export licenses for uranium or uranium oxide.  How
could firing uranium ordnance into enemy territory be construed to
not involve an export of those substances?