[ RadSafe ] [Fwd: RE: uranium combustion produces how much UO3(g)?]

[Eric D]

I am a little late in responding to this post and I apologize.  The
reference quoted by Mr. Salsman for describing the composition of the
particles in the DU aerosol is dated (1979).  A great deal of work has
transpired since that time.  I would like to discuss as many of the points
below as I can.  The most thorough study done to date is the recently
released Depleted Uranium Capstone Study (2004).  The aerosol analysis did
look for and found small quantities of UO3 in the form of schoepite.  For
reasons that are beyond my expertise, separating UO3 from U3O8 was difficult
and it was assumed in the study that UO3 was present whenever U3O8 was
found. The Capstone Report can be found at
http://www.deploymentlink.osd.mil/  


I read the paper by Dr. Alexander and found it extremely useful for other
projects that I am currently working on.  The science is out of my comfort
zone but the experimental setup and the purpose of the work were clearly
stated in the article - study the uranium released in a LOC in a spent fuel
storage facility by transpiration.  The experiment determined the
transpiration rates of uranium and the forms of uranium that occurred when
dry air, dry argon and pure oxygen with and without water vapor at
temperatures that ranged from over 1000K to over 2000K.  The starting
material was depleted fuel rod pellets (not uranium metal) that were crushed
and then oxidized in a platinum crucible at 850K.  In each case the starting
material for the experiment was U3O8 or a mixture of U3O8 and UO2 (for the
argon). The air experiments were done with dry air and air that contained
10% steam and 50% steam and a partial pressure of UO3 was measured for each
condition.  It was very clear from the paper that the environment was very
well controlled.  I am going to follow up with Dr. Alexander because it is
some very interesting work.

The issue of "uranyl oxide gas" and measurement of UO3 gas/vapor is
mentioned throughout the discussion and each time it is mentioned in
connection with "burning in air." Along with discussing this I would like to
clear up the statement < More than 30% of such bullets' uranium metal
burns in air when they are fired against hard targets.>

This statement is partially correct.  The work done by Gilchrist I believe
had 30% but the amount varies based upon the hardness of the target. Not all
of the expended portion of the penetrator ignites.  The 30% refers to that
portion of the round that is "expended" during penetration.  The main
difference is the environment the DU is in when it ignites.  It is not the
pristine air used in the experiment being quoted. From the moment of impact
the DU "fire-flies" (colloquial term we used to describe the portion of the
DU that ignited) are burning in a particle-rich environment that is a
combination of all the materials in the armor, and once penetration occurs,
all of the materials inside the vehicle.  We were able to observe the
dynamics inside the vehicle using ultra-high speed cameras and saw DU
fire-flies for fractions of a second followed by a dense dark smoke that
dissipated over time. These particles aid in rapid condensation.  The
particle morphology in the Capstone report is extremely interesting and in
my personal opinion supports rapid condensation of vapors produced.

< Inhalation of uranium combustion fumes is suspected in major
illnesses reported in veterans and civilians of the February,
1991 Gulf War.>

This is the first time I have seen the word "fumes" used in describing DU
internalizations.  All of the many US, International and UN, studies and
independent reviews done to date are in direct conflict with this statement.
There are good summaries of each at http://www.deploymentlink.osd.mil/ 

< But the portion of UO3 which doesn't condense disperses further
and faster than the aerosols, and are absorbed directly into the
bloodstream if inhaled, dissolving immediately to uranyl ions
which cause chromosome damage leading to immunological disorders
and congenital malformations in the children of the exposed.>

The message this statement is conveying is incorrect.  Rapid dispersal
yields a rapidly reducing concentration which in turn rapidly reduces risk.
>From a radiation dose perspective (chromosomal aberrations) a more soluble
compound poses far less radiation risk then a compound of lesser solubility.
There is no evidence supporting the claim of congenital malformations in
children of people exposed to the low very levels of exposure that would
occur.  The evidence from the VA follow-up of veterans inside vehicles at
the time the vehicles were struck is to the contrary.  Immunological affects
of very high concentrations of uranium in the body (as with embedded
fragments) have been undertaken at AFRRI and the results are posted, I
believe, on their web site.  I would be interested in reading the studies
that support this particular statement.

Sorry for the long post.

Eric Daxon