orwell2013
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Low level alpha-radiation emitting agents - safety aspects
I have problems to find info regarding real aspects of threat concernig dealing with such substances like Thorium-232 nitrate, uranyl nitrate and
uranyl acetate. I'm couriuos how dangerous could be accidental oral or inhalation exposition to even minor quantities of them? Is it safe to operate
with this without a hazmat suite and radiation-level meter? Or maybe my cares are an overkill? 
How much of it is actually needed to develop ARS/cancer/leukemia with acute exposition by swallowing or inhalation? I found out that those are likely
to be disposed by the body if the exposition is once and/or is little... Right?
Thanks in advance
P.S. My question is related TO SAFETY WITH DEALING WITH THOSE (!!!) and NOT how to poison/kill anyone! So NOT LOCKING this thread is highly WELCOMED !
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Endimion17
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Those are not low level alpha-emitters. Those isotopes are, but those samples aren't. You've completely forgot about their daughter atoms which can be
furiously radioactive.
Uranium compounds are mostly toxic (heavy metal). Thorium compounds have an additional kind of weak radiotoxic effect.
Oral consumption is dangerous for kidneys. Inhalation is very dangerous.
If you're an amateur, don't toy with those things.
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Hexavalent
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I attest. If you just want to see a needle go up and hear a noise on your Geiger counter, then a tiny amount of 241Am can be found in smoke
alarms inside the detector itself.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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woelen
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Buildup of daughter isotopes is possible, but the net radiation level never will exceed more than a small factor of the initial radiation level (e.g.
a factor of 5 or so, but that's all).
Suppose you start with 238U. This breaks down through a series of daughter products and the chain has a length of a few elements (5 to 10 products
until some stable isotope is reached). All of these daughter products are shorter-lived than the original 238U. If this 238U is in a closed vessel,
then after a certain (long) time there will be a steady state situation in which all isotopes remain present at roughly the same amounts (daughter
products are produced and created at the same rate). Suppose a daughter product is produced which has a half-time 1000000 times as small as 238U, then
the molar amount of this daughter-product at steady state will be 1000000 times as low. Initially it will be lower, but it goes asymptotically to the
factor of 1000000. Just do the math (write out differential equations) and then you'll see. So, weakly radioactive products like uranyl nitrate and
thorium salts will never become ferociously radioactive.
My conclusion hence is that natural or depleted uranyl nitrate and thorium salts do not pose a significant radiation risk. Only if they are swallowed
or dust is inhaled I can imagine that there is some radiation risk, but I think that in such situations the chemical risk is higher (both metals are
very toxic heavy metals and are at a similar level of toxicity as lead, cadmium and mercury).
You can work with these without special radiation suits. You must be careful with them, simply because of their chemical toxicity, but the
radioactivity of these to my opinion only is a minor risk. Alpha particles do not make it more than a few tens or hundreds of microns in solid and
liquid matter and beta particles (either normal beta and positrons) may reach a few mm in glass and already is shielded by a thin sheet of metal.
Gamma rays have a better option of reaching you, but the amount of gamma radiation from such sources is VERY low and gamma rays also are much less
ionizing and may simply pass through your body. Overall I would not worry at all about the radioactivity of these substances.
It becomes another matter with enriched uranium (e.g. nearly pure 235U) and stuff like neptunium or even worse plutonium. But in practice you never
will encounter anything like that.
[Edited on 15-4-13 by woelen]
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watson.fawkes
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Quote: Originally posted by woelen  | | My conclusion hence is that natural or depleted uranyl nitrate and thorium salts do not pose a significant radiation risk. Only if they are swallowed
or dust is inhaled I can imagine that there is some radiation risk, but I think that in such situations the chemical risk is higher (both metals are
very toxic heavy metals and are at a similar level of toxicity as lead, cadmium and mercury). |
The inhalation
risk from alpha emitters is rather high. They are chemically active exactly because they decay. As the alpha is emitted, you not only have the alpha
itself but also an actinide ion in a (2-) state, which is about as potent as oxidizer as there is. The alpha loses its kinetic energy by knocking into
molecules and knocking off electrons, with concomitant radical formation. Think of each decay as a hot poker of reactive ions.
As I recall, even depleted U has more toxicity from its radiation profile when inhaled or ingested than the radiation-free chemical toxicity. I don't
have a reference to cite for that; sorry.
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woelen
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As I wrote, inhalation is a risk, but this is true for nearly all toxic chemicals. I have the impression though that inhaling dust of e.g. HgCl2 is
worse than inhaling dust of uranyl nitrate, but both are bad!
What I wanted to say, though, is that uranyl salts and thorium salts can be dealt with in a safe manner without special suits and special radiation
detection equipment. You have to be careful with them, but they are not instant death in a bottle. You still can buy green-glow glass beads and that
kind of things and these contain U-salts in low quantities (IIRC a few percents).
[Edited on 16-4-13 by woelen]
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orwell2013
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| Quote: | | Uranium compounds are mostly toxic (heavy metal). Thorium compounds have an additional kind of weak radiotoxic effect. |
Are you sure thorium is not a heavy metal?
| Quote: | Those are not low level alpha-emitters. Those isotopes are, but those samples aren't.
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In case of uranium the isotope included in uranyl salts is much lower level alpha emitter but probable it is. Thorium -232 is the main isotope of
thorium family and definitely IS a low level alpha emmiter. I have an radiological (!) and toxicological hazard warning on the label of the container.
| Quote: | | Oral consumption is dangerous for kidneys. Inhalation is very dangerous. |
Due to acute chemical toxicity or to radiotoxity and accumulation ?
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Endimion17
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woelen, the samples will never become ferociously radioactive because the amounts of ferociously radioactive radioisotopes inside are very small. Even
with that in mind, it is dangerous, especially with thorium.
It's not dangerous in the way that would require beta-ray blocker suits or lead plates or alpha-active dust filter masks if you work with couple of
grams every now and then without creating airborne dust like calcinating nitrate to oxide, but bottles filled with thorium compounds in amounts
present as chemical reagents (50 g, 100 g, 250 g) are quite loud on gamma counters. I wouldn't go near those things with my balls, and it's best to
obtain a healthy distance, at least half metre, and a lead pig would be nice, too, if it stays in the lab.
Given the usual sloppiness of amateur chemists, the dispersal of the material would make a workbench and drain contaminated and quite active when
checked with counters. Honestly, I have no idea how such reagents even cross national borders because they should be easy to pick up at customs.
Natural uranium or depleted uranium compounds (almost every U-reagent is depleted), there's hardly any difference. Enriched uranium would pose a
neutron radiation threat if significant quantities are present at close location, and that will, of course, never happen because such material is
simply off limits.
I've said they have an additional radiotoxic effect. Simple heavy metal toxicity and radiotoxicity encountered at heavy isotopes are mixed
together in a spectrum, and not easy to discern.
| Quote: | | In case of uranium the isotope included in uranyl salts is much lower level alpha emitter but probable it is. Thorium -232 is the main isotope of
thorium family and definitely IS a low level alpha emmiter. I have an radiological (!) and toxicological hazard warning on the label of the container.
|
I'm not saying it is not an alpha-emitter. I'm saying you can loudly hear the samples of thorium salts on gamma counters because of thorium's
gamma-active daughter radioisotopes.
How much of the nitrate you have? Standard 50-100g? I suppose it's inside a glass reagent bottle. Take a gamma counter and put it directly over the
glass. You'll hear a nasty surprise. Not even a decent lead sheet will stop it.
| Quote: | | Due to acute chemical toxicity or to radiotoxity and accumulation ? |
I'd say oral consumption of uranium compounds is mostly dangerous because of heavy metal toxicity. Tubes inside kidneys are very susceptible to
uranium and just fail.
Inhalation would be more in the radiotoxic part of spectrum. Lungs don't have special mechanisms that could quickly remove such matter, so alpha
radiation inside intracellular fluid of alveoli would be a constant source of water and oxygen radicals which would irritate the tissue, leading to
inflammation.
[Edited on 16-4-2013 by Endimion17]
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Endimion17
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I wouldn't worry too much about the uranium compounds. They can remain in plastic containers. Any stray beta will be blocked. Alphas can't get out,
and gammas are weak and they aren't abundant enough. Keep a healthy distance and ventilate the room to be absolutely safe. For example, if you work in
your lab 8h/day and the weak gamma source is in the wooden drawer right in front of your genitals, that would not be a good idea.
As for thorium, keep the bottle at minimum 1 m distance and put it behind few centimetres of lead.
I'm actually describing mild overkill measures, I hope you understand.
Of course, this is just radiation protection. Rays.
Radiochemical protection is much more complex. If you want to do radiochemical experiments, I'd recommend analytical experiments with uranium. Low
concentrations, low quantities. Any "cooking" approach is not something I'd recommend to anyone.
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woelen
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Btw, what interesting things can be done with thorium compounds? I have no experience with their chemistry, but isn't it simply a colorless ion which
only can occur at +4 oxidation state and which only has colorless salts and complexes? What is a typical application of thorium salts?
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Endimion17
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I've never done anything like that. As far as I know, thorium is rather boring if someone wants colours. Maybe some organic complexes give off slight
tints, I don't really know.
Its halogenides are transparent to some parts of the IR spectrum, so they're used for special lenses. It was a more common practice in the past, so
it's possible that if you've got an older camera, your lenses might contain thorium. They become yellow with age due to radiation-induced damage, but
it's (at least mostly) reversible if UV rich light such as strong noon sunlight is passed through them for few hours.
Apart from obsolete x-ray contrasts and heating mantles, fluoride is used in thorium nuclear reactors...
If I find the time, I'll look up for some analytical experiments that detect thorium.
Uranium is a much more interesting element that comes in many coloured oxidation states.
<iframe sandbox width="420" height="315" src="http://www.youtube.com/embed/Nq91FyX8zAI" frameborder="0" allowfullscreen></iframe>
Unfortunatelly, I've never had a chance to do such experiments.
[Edited on 16-4-2013 by Endimion17]
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phlogiston
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I work with uranyl acetate sometimes in a lab, and it is not very dangerous. Just use gloves and labcoat and work cleanly. I also work with
radioactive compounds (mostly 14C, 3H, 32P, 35S isotopes) and even those do not require the sort of measures (hazmat suits) you describe. Just a good
pair of gloves, labcoat and perform regular checks around the lab for spills (door handles, benches, equipment/control knobs etc)
I am surprised that this forum, which sneers at 'chemophobia' is so full of people that think radioactivity = instant death.
It is by no means easy to obtain hazardous quantities of radioactive materials. A few grams of natural/depleted uranium or thorium are not
particularly dangerous. Certainly not more dangerous than many of the non-radioactive chemicals discussed here on a daily basis.
The radioactivity is actually very helpful in the sense that it is so easily measured with such high sensitivity that is easy to locate even tiny
spills and clean them up. You can't do that with lead/mercury/cadmium nitrate for instance.
[Edited on 26-4-2013 by phlogiston]
[Edited on 26-4-2013 by phlogiston]
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orwell2013
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Is the thorium nitrate soluble in acetone? How much?
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