[ RadSafe ] uranium trioxide gas exposure patterns (was: ... RE: Gardner Sellafield cluster)

[James Salsman]

John Andrews wrote:

> [Uranium trioxide gas] blows away.  It does not stay 
> where it is generated and deposit at the rate of 60 cm/year. 
> It blows away.  Far away.  It dilutes.  It mixes.  It disperses.
> It does not stay around.  Soon it is gone.  That is my point.

Sure, I'm not disputing that, but chlorine gas blows away too,
and does so more quickly because it is a smaller molecule.  That
hasn't kept it from being used as a chemical weapon, and I'm sure
you know that you don't want to be anywhere near a chlorine gas leak.

The difference, of course, is that chlorine has an immediate effect,
while uranium takes a while to make it from the lungs to the kidney,
if there is enough to cause kidney damage, and to the testes, where
it will accumulate over repeated exposures and lead to an increase
in the incidence of birth defects, even if there isn't enough to
cause kidney damage from any single exposure (it clears from the
kidney, but accumulates in the testes, bone, and brain, where it is
known to cause significant behavioral changes in mammals.)

Multi-milligram exposures from UO3 gas are likely without being
near the point of impact.  The most widely used form of DU ordnance
is the 30 mm armor piercing incendiary round, each with 292 grams
of uranium (98% U-238.)  These bullets are fired from automatic
weapons, typically at over 10 rounds per second, e.g. from the
Apache helicopter's M230 gun, in bursts of a few seconds each.
They are designed to burn on impact, but will only do so if they
strike a hard target, and then only about 70% of each round burns.
So, assume if 20 rounds are fired in a single burst, 10 might
burn, resulting in two kilograms of uranium in combustion products,
at least 200 grams, and probably 400 grams of which should be
uranium trioxide.  The convection of the fire will cause the plume
to spread out into an initial cloud, but after the gas cools, it
will spread less quickly than chlorine.  Based on chlorine cloud
behavior, I think it is reasonable to assume that such a cloud
would occupy about 1,000 cubic meters after 10 minutes or so in
a moderate wind.  That would mean each lungful (5 liters) would
contain about 1.5 milligrams of elemental uranium in monomeric
uranyl oxide form, and so a minute of exposure would probably
result in deposition of at least a few milligrams, just from a
single, two-second burst of machine gun fire, 10 minutes downwind.

The question I am least certain about is the deposition rate.
For some reason, even though we have lung absorption studies of
granular uranium trioxide dust, as far as I and Gmelin can tell,
nobody has ever tested the toxicity of uranium trioxide gas,
probably because even though it has been known as a uranium
combustion product since 1961, it is "not infrequently ignored."

Sincerely,
James Salsman