Jeff Tsai on thu 15 jan 04
This is a question. I neither have the knowledge of glazes or of Uranium to
feel confident to promote or detest it's use in glazes as recent discussions
have been.
My question is just, are all types of Uranium hazardous? This is just
something that has been bouncing in my head while reading the Uranium posts. I know
that one particular Uranium isotope is the kind used for atomic weapons,
"weapons-grade" uranium. I also know that there are other Uranium Isotopes with
varying amounts of...uh, nuetrons I believe. Are all those other variations, other
isotopes, also as lethal and dangerous as the the weapons-grade Uranium?
I realize this is not a ceramics question, but some of you seem rather well
infrmed on chemistry in general.
-jeff
Joe Coniglio on fri 16 jan 04
Jeff asks if there is a safe form of Uranium out there.
------------
Funny, the governments of Great Britain and the US think there is.
During the Gulf war and in the current conflict in Iraq virtually tons of
DU---That's Depleted Uranium has been steel jacketed and used in
artillary shells because it is very heavy. Uranium decays into Lead on
the periodic table. Uranium is heavier than Lead.
--So what to do with all the low level, spent Uranium slag from refining
and power plants?? Let's put it in an artillary shell and lob it on a
hapless enemy.
When the shell disinegrates it leaves a radioactive power residue all
of the place.
Gulf War Syndrome hasn't adequately studied the obvious, the
sicknesses probably came from US and UK soldiers being down
wind from their own spent munitions.
http://www.cadu.org.uk/
http://www.iacenter.org/depleted/du.htm
http://www.iacenter.org/depleted/mettoc.htm
http://www.gulflink.osd.mil/faq_17apr.htm
http://www.stopnato.org.uk/du-watch/
----
But it sure makes a pretty yellow.
Steve Slatin on fri 16 jan 04
Jeff--
The short version of the answer, though it drives some
people to distraction, is that uranium -- the metal --
is a toxin. Many of the metals in glazes are toxins,
and though most folks avoid lead, say, and maybe cadmium,
probably insufficient attention is paid to the toxicity
of the other metals. So yes, Uranium is hazardous in
any form, as are many other glaze constituents.
Edouard B. recently posted a link to an article he
Translated from the French on metabolization of=20
Uranium. Read this for a quick sanity check.
All uranium is radioactive. (This is to say, it suffers
spontaneous radioactive decay.) In naturally occurring
uranium (except from some sites in Gabon) the two primary
uranium isotopes exist in the proportions 99.3% U-238 and
0.7% U-235. The 235 is the stuff that's fissile, the
238 isn't useful in nuclear power or weapons. The 235
has to be enriched to 3% to be useful in power reactors;
the enrichment necessary to create weapons-grade uranium
is much higher. Naturally occurring Uranium also includes
a truly tiny amount of one other isotope -- U-234,
approximately 5 thousandths of one percent.
If you have U-235 and you bombard it with neutrons, you
will start to get a fission reaction -- the nucleus=20
breaks up, giving off additional neutrons. These neutrons
have quite a bit of energy, and you wouldn't wish to be
exposed to too much of them. =20
But a plain chunk of uranium metal (or a pile of Uranium
Oxide, known as "yellowcake") doesn't give off neutrons and
you don't have fission reactions ordinarily in nature (the
one exception being the Gabon thing, mentioned elsewhere --
do a Google search if you want to know more). U-235 and
U-238 give off primarily alpha radiation. An alpha
particle is like a nucleus with no electrons with two=20
neutrons and two protons {forgive me for the extremely poor
physics in this description} and has so little energy that
ordinarily your skin protects your body from the radiation.
That's not a misstatement, your skin protects you.=20
The next question, then, given that the radiation is mostly
relatively less-dangerous alpha emissions, is what is the
rate of decay of U-235 vs. U-238. Radioactive decay is
measured in "half life" the length of time it takes for half
of all of the atoms in a sample of pure metal to decay.
The half life of U-235 is 713 million years; that of U-238
Is 4.5 billion (thousand million) years. A cite for this is
http://www.reachingcriticalwill.org/resources/edkit/22urakey.pdf
So given the various concentrations of uranium in different
Compounds, how much radiation can you get from it? There's
A neat calculator -- I haven't checked its results -- on
http://www.antenna.nl/wise/uranium/rccu.html that does these
calculations for you.
This gets me back to my soapbox. (Sorry, folks.) The
hazard to using uranium, for the potter, is metal toxicity,
not radiation. The health Physics Society
http://hps.org/publicinformation/ate/q754.html
says "Depleted uranium and natural uranium both consist=20
primarily of the uranium isotope 238U. They are only very=20
weakly radioactive and are not hazardous radioactive=20
toxicants, but uranium is a weak chemical poison that can=20
seriously damage the kidneys at high blood concentrations."
Later on, same article, they say=20
As to its "heavy metal" toxicity, the closest analogy is lead.=20
However, metallic lead has considerably higher toxicity than=20
metallic uranium. Compounds of lead are much more hazardous=20
than compounds of uranium since uranium tends to form=20
relatively insoluble compounds which are not readily absorbed=20
into the body. Also, lead within the body affects the nervous=20
system and several biochemical processes, while the uranyl ion=20
does not readily interfere with any major biochemical process=20
except for depositing in the tubules and glomeruli of kidney=20
where damage may occur at high concentrations. This kidney=20
damage is dosage dependent and somewhat reversible. The=20
occupational exposure threshold limit air concentration value=20
is 0.2 milligrams uranium per cubic-meter based on chemical=20
toxicity.
The corresponding OSHA standard for lead
http://www.atsdr.cdc.gov/HEC/CSEM/lead/standards_regulations.html
Is 50 MICROgrams per cubic meter of air. (1 microgram is .001=20
Milligrams.)
And, just for kicks and jollies, consider this -- maybe you want
a yellow glaze, so you go with vanadium to avoid 'dangerous'
compounds. OSHA standards for vanadium are twice as demanding as
for uranium. http://www.cdc.gov/niosh/rtecs/yw258960.html
OF COURSE THERE'S ALSO A RISK TO THE USER OF POTTERY -- IF THE
GLAZE LEACHES. =20
If you use any glazed item for food use, you should make sure=20
it's got a stable glaze. NO ONE SHOULD MAKE OR SELL POTTERY=20
WITH POSSIBLY UNSTABLE GLAZES IF THEY WILL BE USED FOR FOOD.
The reason why people react to the thought of Uranium is that=20
there's a mystique about it. An X-ray technician in a hospital
typically gets many times more radiation exposure each year
than a worker in a uranium processing plant, though. And=20
for serious risks, read the threads here when people are trying
to clean stuff. Folks recommend acetone, methyl-ethyl-ketone,
benzene, etc. These things are toxic. Using them is hazardous.
And they are all fire hazards, besides. =20
I'm going to try to swear off this thread, now, and I'm sorry
For boring folks.
-- Steve Slatin
----------------------------
Subject: Uranium question
This is a question. I neither have the knowledge of glazes or of Uranium =
to
feel confident to promote or detest it's use in glazes as recent =
discussions
have been.
My question is just, are all types of Uranium hazardous? This is just
something that has been bouncing in my head while reading the Uranium =
posts.
I know
that one particular Uranium isotope is the kind used for atomic weapons,
"weapons-grade" uranium. I also know that there are other Uranium =
Isotopes
with
varying amounts of...uh, nuetrons I believe. Are all those other =
variations,
other
isotopes, also as lethal and dangerous as the the weapons-grade Uranium?
I realize this is not a ceramics question, but some of you seem rather =
well
infrmed on chemistry in general.
-jeff
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