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elementcollector1
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Sigh... The only good deposits near me are in Idaho, and these just appear to be random placers - not exactly a good place to start looking. Still,
I'll keep this map in mind if I ever get the opportunity.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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annaandherdad
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The last article I posted says that since new regulations were implemented in the US for disposing of thorium, the production of rare earths from
domestic monazite has virtually ceased. Monazite also sometimes has uranium in it, which as far as I'm concerned would be undesirable. Still, if I
could get my hands on several kg of it, it certainly would be tempting to process it.
Any other SF Bay chemists?
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IrC
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Plenty of places, especially on BLM land where you or elementcollector1 could pan on a weekend camping trip along a stream without worrying about
someone bothering you. Get an empty 5 gallon plastic paint bucket, a shovel, and a couple items from Garrett: http://www.garrett.com/hobbysite/hbby_gold_pans.aspx
http://www.garrett.com/hobbysite/1650200_14in_sifter_classif...
http://www.garrett.com/hobbysite/1650400_super_sluice.aspx
Set the screen on the bucket and fill it from the stream bed using the shovel, and the pan repeatedly filled with water is used to wash it down into
the bucket. When you have a decent amount of finer material in the bucket use the pan in the stream filling it half full from the bucket and washing
this material down to black sand. You pie pan will lose most of the black sand. The ridges in the 15" Garrett pan were designed with much
experimentation to keep the sand as you wash out the rest meaning many times less work to collect what you want than the smooth pie pan. In one day of
fresh air outdoors you could fill the bucket with black sand. Don't forget to look for Gold flakes and small diamonds in the black sand as well.
In the 80's I worked in R&D all week in Phoenix, waiting to spend my weekends 90 miles North just below Prescott, Az working my two Gold placer
claims. Great way to get the hell out of the city every week even if only for a little while. I ran a small sluice box and used a pan to process the
output from it. For your purpose panning would do as well, since you do not need to process large amounts looking for Gold.
"Science is the belief in the ignorance of the experts" Richard Feynman
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annaandherdad
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IrC, thanks a lot! That's some really useful information. I'll have to see if any of those thorium placer deposits in North and South Carolina are
on public land. Also, my daughter is really interested in going to into the Sierras to pan for gold, although she might lose her enthusiasm if we
actually did it.
Any other SF Bay chemists?
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IrC
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http://www.blackcatmining.com/mining-equipment/mini-sluice.c...
Something like this would provide pounds of black sand with relatively easy work, you set it up on the side of the stream to allow water to run
through it as you shovel in gravel from the stream bed. You remove the carpet from the sluice every so often and wash it inside your 5 gallon paint
bucket half full of water. This way you clean the carpet, the black sand settles to the bottom of the bucket. Put the carpet back in the sluice and
run it again. Eventually you carefully pour the water out of the bucket leaving pounds of black sand in the bottom to take home and process. They have
a page of tutorials: http://www.keeneeng.com/resources.html
Actually a lot of weekend fun as a hobby. I ran a 3.5 inch dredge and recovered about 14 oz Gold in 83 on my weekends. Was a nice way to get fresh
outdoor air and sun to combat stress from the work week.
http://www.blackcatmining.com/
This place has about the lowest prices. You use the pans to work the output from your sluice box, not really required if the black sand is your goal
instead of Gold obviously. Would be a fun camping outing for you and your daughter. There are more places you can find to do this with no problems
than you may think. Without worrying about the 'guy with a shotgun' you mentioned earlier. Many do this as a hobby.
Watch a few vids on how to operate the gear before you go out: http://www.youtube.com/results?search_query=Sluice+Box
http://www.youtube.com/watch?v=F6KRHey8Ors
http://www.youtube.com/watch?v=4OR1MlXneFo
Edit: forgot to add a couple Gold panning vids:
http://www.youtube.com/watch?v=ZqpxZ9p3hao
http://www.youtube.com/watch?v=W2db-nGQgWo
Don't forget to pick a couple nicely shaped lightweight shovels.
[Edited on 5-6-2014 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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elementcollector1
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Used to gold pan as a hobby, so I have everything but the sluice...
14 oz?! Where were you, Yukon?
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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IrC
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I had 2 placer claims outside Prescott, Arizona back in those days. Eventually moving from Phoenix in the 90's I could not keep up the yearly filing
and assessment work so someone came in and filed over me. Turned out to be a mining company that searched county courthouse records looking for claims
with out of date paperwork so they could grab them forcing the owner out. I mean if you were a day late these people jumped on it. All over Arizona,
and most other states they have people looking. Then around 94 Clinton repealed the 1873 mining act so it no longer mattered.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Dan Vizine
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Quote: Originally posted by annaandherdad  |
They estimate 140g of K in a human body of 70kg, the nominal value they use. Due to the content of K40, this translates into 4,400 Bequerel (they
cite this as 266,000 decays per minute). The say that 89% of the decays are beta decays with a maximum energy of 1.33MeV. When I work this out, it
comes to 8.4x10^-10 J/sec = 1.2x10^-11 J/kg-sec, assuming 70kg body, which is 3.6x10^-4 J/kg-year, or nominally 36 millirad/year. But the article
quotes the value of 16 mrad/year. Now I believe the rad is 100ergs/gm, before any biological effect fudge factors are applied. But the article says
that the beta decays of the K40 exposes the human body to only 16mrad/yr. So did I make a mistake? Maybe the difference is accounted for by the fact
that the 1.33MeV quoted is the *maximum*energy per beta decay; since some energy is carried off by the neutrino, the *average* energy deposited in the
tissues would be less, maybe bringing the number down to 16mrad/yr. I'm just guessing about this.
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When I repeat your calculations I get the same answer within rounding errors...
0.89(266000 dis/min) X (1 min/60 sec) X (1.33 MeV/dis) X (1.60x10E-13 J/MeV) X (1/70 kg) X (31500000 sec/yr) X (100 rad/J kg) X (1000mrad/rad) =
38mrad/yr
Your reasoning re. average vs. peak MeV/disintegration is the only logical answer. This shouldn't have been glossed over, it leaves you scratching
your head.
I haven't looked at the related Th calculations yet, but lunchtime is almost over. They will get looked at this evening, hopefully. Right now, it's 70
F outside and so it's time to get this starting material broken up and divided into a few lots.
Update: What a nicely behaved free-flowing solid. There were loosely consolidated clumps that broke easily. The resultant material resembled the fine
granular NaOH (formerly sold by Red Devil) in terms of density and texture. Very easy to be neat when weighing and transferring.
If no other stuff comes up, maybe I'll get to the first reaction this weekend. Still debating if I want to use my sintered glass or buy something
disposable...guess I'm off to eBay to see what's available....
[Edited on 8-5-2014 by Dan Vizine]
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annaandherdad
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And while we're on the subject of thorium, there is the story of Thorotrast.
http://en.wikipedia.org/wiki/Thorotrast
Gives interesting information about what happens to you (and your life expectancy) if you eat thorium oxide.
Any other SF Bay chemists?
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annaandherdad
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Dan, I didn't see your answer sooner. I'll do so as soon as I can.
Any other SF Bay chemists?
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Dan Vizine
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Robert,
I was doing some calculations on the daughter products just to see the magnitudes and ranges involved.
Only 1/2 pound of the pound was mine. The MW of the nominal tetrahydrate is 318.12, so the ~1/2 pound (actually 227 g) is 4.30*10E23 molecules.
I calculated average lifetimes from the half-lives.
I derived the # of atoms of each species by multiplying 4.30*10E23 by the ratio of its half-life to that of 232Th. From that I derived the average
number of disintegrations per second and the number is 9.5*10E5 for all daughters except 212Po which shows 6.1*10E5 per second and 208Tl which shows
3.4*10E5 per sec due to branching in the decay chain.
All of the disintegration/sec figures are self-consistent except for the parent 232Th. I can't find my error. I get 6.8*10E5 here. Essentially all
atoms are 232Th, so there are 4.30*10E23. The half-life is 1.4*10E10 years, or 4.4*10E17 sec for an average lifetime of 6.3*10E17. Dividing #
molecules by average lifetime of the 232Th in them, gives me 6.8*10E5 which is only about 72% of the activity of the daughters(?!).
Some of the abundance figures were interesting though:
about 246 trillion 228Ra atoms
about 30 billion 228Ac atoms
only about 76 million 220Rn atoms
while for 212 Po, if i did this correctly, only 1 atom exists, on average, for 3 msec/sec. For the other 997 msec, on average, 0 atoms of 212Po exist.
The amounts are truly tiny.
I found it perplexing that the entire decay chain (and the others) consists of only one of two things, either alpha or beta emission. Other processes,
like positron emission, don't seem to make notable contributions I guess?
Is it valid to multiply the activity times the sum of the energies for all steps of the 232Th --> 208Pb chain (42.6 Mev) to get the total radiated
energy? Meaning 9.5*10E5 disintegrations/sec times 42.6 Mev/disintegration times 1.6*10E-13 J/MeV?
[Edited on 11-5-2014 by Dan Vizine]
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annaandherdad
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Dan, I can't do justice to your message tonight, I'm giving an exam tomorrow and it isn't ready yet. Just wanted to mention some things I learned.
Some of the alpha decays in the thorium decay chain are accompanied by gammas. The wikipedia article I was looking at (on decay chains) just gives
the total energy of each decay, without breaking it down.
http://en.wikipedia.org/wiki/Decay_chain#Thorium_series
I don't know which ones, but a little research would find the answers. I also heard that the reason they use Americium (I think it's 242) in smoke
detectors is that it is an alpha decay that is free from gammas, so the radiation is confined to the small ionization chamber.
I have a clunky old yellow geiger counter from the 60's, it has a shield that you're supposed to remove in order to allow it to detect beta particles
(otherwise the shield blocks them). It never detects alphas; with the shield up it only detects gammas. It works, and registers counts when I open
my little bottle of thorium nitrate, but the sound is pretty faint and I'd like to get a better one. bfesser has some reports of a good, modern
geiger counter. At some point I want to invest in one.
As for the beta decays, I gather from the wikipedia article that they're all electron emissions; the little arrows are all to the northeast on the
chart of nuclides. These could be accompanied by gammas, too, I don't know.
The decay of K40 is more complicated, there there is a certain branching ratio for electron absorption and for positron emission.
Any other SF Bay chemists?
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Dan Vizine
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Hi Robert,
As I understand it, there is an inevitable gamma ray component to these decay chains for two related reasons;
1) Bremsstrahlung from beta decays
2) Need for the nucleus to throw off energy after alpha or beta emission perturbs it
Here is the breakdown of the energies/step
232Th-->228Ra 4.1 MeV
228Ra-->228Ac 0.05 MeV
228Ac-->228Th 2.1 MeV
228Th-->224Ra 5.5 MeV
224Ra-->220Rn 5.8 MeV
220Rn-->216Po 6.4 MeV
216Po-->212Pb 6.9 MeV
212Pb-->212Bi 0.6 MeV
212Bi-->212Po 2.3 MeV
212Po-->208Pb 9.0 MeV
208Tl-->208Pb 5.0 MeV
A lesson I have learned, and recently re-learned, about radiation: It's never as simple as it seems, even on the rare occasions that it seems
simple.....
Is gamma ray production from Bremsstrahlung proportional to the ke of the emitted particle? It seems it would have to be.
[Edited on 13-5-2014 by Dan Vizine]
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annaandherdad
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Hi, Dan. When you computed the activity (decays per sec) of the daughter products, you multiplied the number of atoms times the lifetime, right? And
the lifetime is the half-life divided by log 2=0.69. I suspect your 72% is actually 69% = log 2.
Also, it's Th(NO3)4(H20)4, right? That's what wikipedia says, I don't have my bottle with me right now. I get 552 for the molecular weight.
In any case, you've got a substantial fraction of a mole. Here are my results for the amount of each daughter species, in units of mole (daughter)
per mole (parent 232 Th):
228 Ra 4.09 x 10^-10
228 Ac 5.07 x 10^-14
228 Th 1.36 x 10^-10
224 Ra 7.08 x 10^-13
220 Rn 1.25 x 10^-16
216 Po 3.27 x 10^-19
212 Pb 8.64 x 10^-14
212 Bi 8.19 x 10^-15
212 Po 4.32 x 10^-25
208 Tl 1.48 x 10^-16
Notice that on average, there is less than one atom of 212 Po for every mole of 232 Th.
And I get an activity of 9.41 x 10^5 Bequerel/mole for the parent 232 Th (in my earlier post I estimated this at 10^6).
On to bremsstrahlung.
Any other SF Bay chemists?
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Dan Vizine
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Hi Robert,
My replies in blue:
When you computed the activity (decays per sec) of the daughter products, you multiplied the number of atoms times the lifetime, right? And the
lifetime is the half-life divided by log 2=0.69. I suspect your 72% is actually 69% = log 2.
Actually, I didn't. I mistakenly divided by average lifetime. Oops.
Also, it's Th(NO3)4(H20)4, right? That's what wikipedia says, I don't have my bottle with me right now. I get 552 for the molecular weight.
Yes, it's nominally the tetrahydrate.I feel [slightly] less silly about this error. I referenced the American Elements
website to get an anhydrous MW of 246.04 (image attached), and ignoring common sense, I added 4 mol H20 (72.08) to get 318.12.
Notice that on average, there is less than one atom of 212 Po for every mole of 232 Th.
Yes, even in my flawed calculations I got that result. That was rather fascinating.
Well, I should adjust my numbers to see if they jive with yours.
[Edited on 13-5-2014 by Dan Vizine]
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annaandherdad
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Hi, Dan, on thinking about gamma rays I'm trying to separate what I know for sure, what I've just learned recently, and what I think is right based on
general principles but where I could be wrong or have an incomplete picture. So with that disclaimer, here's what I think I know about this
situation.
One reason for gamma rays in radioactive decay is that an alpha or beta transition typically takes one nucleus into an excited state of another, which
then decays by an electromagnetic transition to its ground state. In this situation, the gamma ray comes off with a definite energy (the difference
in the energies of the two nuclear levels). It's also possible that a cascade of transitions and gamma rays will be followed to reach the ground
state, instead of a single transition.
Another mechanism for the production of gammas in radioactive decay is bremsstrahlung, as you say, but based on what I know I believe gamma rays by
this mechanism should be less frequent and of lower energy than those described in the previous paragraph. In addition, these gammas (or x-rays,
photons by whatever name you want to give them) will come off with a continuous spectrum of energies.
Bremsstrahlung is a somewhat confusing name, because it's used for different types of physical processes. One if them is when a high speed, light
particle, typically an electron or muon, is passing through matter. When the particle passes close to a nucleus it is accelerated by the nuclear
electric field, and emits radiation (typically one photon) as a result. The energy of the photon follows a distribution; most of them have only a
small fraction of the energy of the particle, but the distribution has a significant tail extended to higher energies, so that occasionally the
charged particle loses almost all of its energy, which is converted into the energy of a single photon. Bremsstrahlung is the dominant mechanism
for energy loss when relativistic electron pass through matter. Electrons from beta decay are typically relativistic when they are created.
This is probably not the kind of bremsstrahlung you are referring to, although in beta decay the ejected electron will undergo bremsstrahlung if it
passes through matter (as it usually does). You are probably referring to the fact that in beta decay the ejected electron may be accompanied by a
photon, which can be thought of as the radiation produced when the electron is created accelerated out of the nucleus (getting a big push from the
nuclear electric field). Based on what I know, this type of event (beta particle plus photon) should be exceptional, that is, more rare than a beta
particle without a photon, because producing the photon requires a higher order of perturbation theory and the probability involves an extra factor
of the fine structure constant (1/137). In any case, when a photon is produced, it has a spectrum of energies, from zero all the way up to the
maximum energy released in the beta decay.
So based on all of this my guess would be that the majority of the most energetic gamma rays from decays such as in the thorium chain will be from
nuclear transitions following alpha or beta decay, with a discrete spectrum.
There are other mechanisms for the production of gamma rays in radioactivity, for example, positron emission will be followed by the annihilation of
the positron with an electron.
As I related, a friend of mine told me that smoke detectors use 241 Am (in an earlier post I guessed that it was 242, it's actually 241) because
their alpha emission is not accompanied by a gamma ray. According to wikipedia, however, that's not quite correct, the alpha decay 241 Am -> 237
Np is accompanied by a gamma ray in a small percentage of the cases. My friend may be right, however, that the low number of gammas is one reason
this isotope is used in smoke detectors, that is, not much radiation escapes from it. Wikipedia says there is 37KBq in a smoke detector.
Any other SF Bay chemists?
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Dan Vizine
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Hi Robert,
The former mechanism is the one I meant for Bremsstrahlung, which roughly translates to "breaking energy". This was the gamma source I wondered about.
But, there isn't much need to wonder about the hazards too much, a wealth of thorium related work has been published over the last 60 - 70 years.
I've assembled a body of information that indicates the relative dangers of 232 Th and 238U. The results also clearly show the different natures of
the the radiological hazard.
In the following passages it is instructive to remember that the alpha particle causes the highest ionization per unit length of path, it is this
radiation which is of greatest concern in considering radiation inside the human body. Externally only the beta and gamma radiations are cause for
concern.
In the processing of thorium materials, decay products fall into several columns of the periodic table and therefore behave chemically in different
ways. Because of the short half-lives of many of the later decay products, the chemical problem is essentially one of handling two elements, thorium
and radium.
When thorium is separated from other isotopes in the decay series, the thorium fraction has only a slight alpha activity. There is no beta radiation
and only a slight amount of gamma radiation (from the 0.09-MeV gamma rays which emanate from Th-228 decay). More on the efficiency of separations to
follow.
However, the activity from the Th-228 side of the chain is quickly re-established. A first equilibrium state is reached in about 36 days (10
half-lives of Ra-224). Activity then declines, as Th-228 decays faster than it is replenished by decaying Ac-228. About 3 years after separation, the
activity is lower than at any other time except immediately after separation. From this point, activity increases until the second equilibrium state
is reached in about 60 years.
After chemical transformations occur, non-thorium fractions contain Ra-228, which has as one of its decay products the strongly active Th-228. An
example of the acute radiotoxicity of some of the isotopes involved can be found in the work on Th-228 by Finkel and Hirsch. They state that Ra-228 is
as toxic as Po-210, Pu-239 or U-233. The 20- to 30-day LD50 for these alpha emiters fall between 36 and 58 microcuries/kg and indicate a toxicity
within the first month after injection twenty times as great as that for Ra-226. The 20- to 30-day LD50 value for Ra-224 was estimated at about 1000
microcuries/kg of body weight. On the activity basis, these LD50 values suggest that when thorium is separated from the radium isotopes, Ra-228
constitutes the main health hazard.
For purposes of better understanding the relative radiological hazards, thorium is often compared with uranium. While the two are considered to be
about the same order of hazard, the nature of the hazards differ.
While the decay rate of Th-232 is only one-third that of U-238, the number of alphas emitted per disintegration of Th-232 is, except for brief periods
of time after separation, three times that of U-238. The total energy of the alpha radiation from thorium is 36.2 MeV. The total energy from U-238
plus U-234 is only 9 MeV.
It is the Th-234 and Pa-234 found with the uranium which account for the beta activity in natural uranium. The beta radiation from uranium in
equilibrium with Th-234 and Pa-234 exceeds that from thorium in equilibrium with all of its daughters. Beta dose rates in contact with infinite
sources would be approximately 240 and 115 mrem/hr for uranium and thorium, respectively. On the other hand, thorium gives considerably more gamma
radiation than does uranium. Uranium dose rates from infinite sources have been estimated at about 10 mr/hr in comparison with 50 for thorium.
So, the results are a little surprising. Now I want to try to apply the thorium dose rate conversion factors to roughly quantify risk.
[Edited on 16-5-2014 by Dan Vizine]
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Dan Vizine
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"So, the results are a little surprising. Now I want to try to apply the thorium dose rate conversion factors to roughly quantify risk."......wow, the
arrogance...
Quantifying risk is more complicated than I ever imagined. I see a certain similarity between just trying to get a very basic understanding of this
area and the actual process of nuclear fission, they are both an ever-broadening series of branches.
Every thing I pursue, be it effective dose, absorbed dose, kerma, infinite sources or whatever, inevitably ends up in it being defined in terms of
many others variables. Usually, I need to look up definitions of a number of these which are, in turn, being defined in terms of several others
variables...etc.
[Edited on 17-5-2014 by Dan Vizine]
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Dan Vizine
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So many details....
powerful stirrer for the Th(OH)4 : check (It's a re-purposed Buchi stirring motor)
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Dan Vizine
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Some suggested practices, collected from the internet:
Chemical SOP’s – Uranium & Thorium
Specified Hazards
a) Both uranium and thorium emit alpha particles, which have a relatively large kinetic energy but due to the (relatively) high mass and charge they
will not penetrate the epidermal layer of the skin. Since keratinized epidermal cells do not have a nucleus and are relatively metabolically inert,
they are basically immune to damage due to ionizing radiation. Therefore the outer layer of skin is an effective shield for alpha particles (the one
exception is the eye where viable metabolically active cells are at the surface). Damage from alpha particles occurs when they are injected, ingested
or inhaled such that the alpha emissions interact directly with viable tissue. If that occurs, alpha particles will cause
approximately 20 times as much biological damage, per unit of energy absorbed, as gamma rays or beta particles. It is important to ensure that
airborne concentrations of uranium be minimized as far below the ACGIH (2006) limit of 0.20 mg/m3 of air as possible and that designated areas are
cleaned when contaminated – this prevents the spread of contamination. Problems can best be avoided by careful control of any finely divided
material and by good hygiene practices.
b) Uranium is more toxic than lead [1], and is radioactive. Uranium exposure can lead to kidney damage and disease,
lung fibrosis and malignant neoplasm formation in the lungs, hematopoietic system damage and leukemia. Thorium [2]
should be treated in a manner similar to uranium.
Activities which could produce airborne particles of uranium/thorium must be performed using the proper equipment.
The following ppe must be worn:
i. Air purifying respirator.
ii. Unvented goggles, if respirator is not full face.
iii. Tyvek suit with booties
iv. Thin walled nitrile gloves
Only use the following personal protective equipment once, check it for contamination and then dispose of it:
• Thin walled nitrile/ latex gloves
• Tyvek suit with booties
• Respirator cartridges (APR, R100 or better)
Decontamination procedures for elastomeric respirator and goggles: (elastomeric respirators and unvented goggles must be decontaminated prior to
storing them.)
1. After removing respirator from face, discard respirator cartridges as contaminated radioactive waste.
2. Use two respirator cleaning wipes (alcohol free), one to wipe the exterior of the respirator and the other to wipe the interior. Use another wipe
to clean the goggles. Be sure to wipe all surfaces. Used wipes must be disposed of as radioactive waste.
3. Disassemble the respirator in accordance with manufacturer recommendations.
4. Wash all parts of the respirator, and the goggles in the mild soap solution/warm water solution prepared before you began clean-up. Do not dump
water in tub down the drain.
5. Rinse washed goggles and respirator components in the sink and set them on paper towels to air dry prior to storage.
6. Set tub of water aside and let the water evaporate from the tub. Once evaporated use the Geiger counter to determine if interior of tub is
contaminated. If tub is contaminated then clean it using a respirator wipe, then use the Geiger counter again to determine if contamination exists.
If the tub won’t wipe clean then note that it is contaminated on the label of the tub. Store the tub in its designated area.
Work Area Decontamination Procedures
1. Use a HEPA vacuum to collect any loose contamination.
2. Use a damp cloth and bucket of mild soap solution and water to wipe contamination that the HEPA vacuum did not collect from contaminated surfaces.
Then use the Geiger counter to determine if radioactive contamination is still present. Repeat process until area is cleaned up, or it is determined
that such work is futile.
3. Set bucket of water aside in a designated are and let the water evaporate. Once the water is evaporated use the Geiger counter to determine if
interior of bucket is contaminated. If bucket is contaminated then clean it using a damp towel and then use the Geiger counter again to determine if
contamination is still present. If the bucket won’t wipe clean then note that it is contaminated on the bucket label. Store the bucket in its
designated area.
4. Towels, rags, and other such items used to clean up need to be disposed of as radioactive waste.
[1] LD50 oral for Pb (in Pb- acid Batteries) is 500 mg/Kg). For rats the LD50/21 days was 6 mg of uranium ore per
kilogram body weight (6mg U/kg). This is comparable to the ORL-RAT LD50 for diarsenic pentoxide (As2O5) which is 8 mg/kg—meaning that it would only
take 600 mg (0.6 g, about half the mass of a dollar bill) of ingested As2O5 to kill off a 75 kg human. The only plus is that U oxides are mostly
insoluble. The RfD for uranium (soluble salts) is 0.003 mg/kg/d based on body weight loss and moderate nephrotoxicity in rabbits
[2] Animal studies: LD50 value: thorium nitrate: 48mg/kg (IVN rat); thorium oxide: 400mg/kg (IMS mice); LC50
value: No information available. Annual limit of intake (human) : 200 Bq;
All of the above simply validates my suspicion that drying the hydroxide and calcining it will be the most difficult step to do cleanly.
[Edited on 29-5-2014 by Dan Vizine]
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blogfast25
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Interesting, Dan. Makes me think about the use of DU in armour piercing conventional tank munitions again...
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Dan Vizine
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Apparently there's more laying around than I realized. A current estimate is that it may take $300 M to clean up the DU in Iraq.
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blogfast25
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If it is more toxic than lead, using it in an application that pulverises it into open air and into a human environment may have been slightly
irresponsible, to say the least.
But I've a feeling you won't find the military carrying out any environmental impact studies...
[Edited on 30-5-2014 by blogfast25]
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Dan Vizine
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I've been giving the prolonged high temperature calcination step the most thought of all. I see it as clearly the most hazardous by a large
margin. This is the step most likely to cause aerosol formation (this and the hydrolytic work up with decomposing Ca causing bubbling), which is
really the only thing I fear in this prep. My thinking has radically changed as this project has progressed. I'm much less worried about gamma
emanations than the feeble ("I can even go through a sheet of paper") alpha particles. This is the exact same reason that plutonium is so toxic.
I had considered two large silica melting crucibles shaped like bowls. Put them together like a clamshell and heat. But in what? My furnace? I'd
rather not contaminate that. So......?
Then this mullite process tube appeared on eBay for only $20. It is 2 inches in OD and a foot long. Wrapping it with Super Kanthal A-1 wire will allow
the 900 C that I need, easily. The cool, open end of the process tube can be fitted with an exhaust tube which will carry all effluents to a mineral
oil trap.
[Edited on 31-5-2014 by Dan Vizine]
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Dan Vizine
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Finally found some time....
To a stirred, clarified, room temperature solution of thorium nitrate tetrahydrate (227 g, 411 mmol) in distilled H2O (2.5 L) was added 28% aqueous
NH3 (317 mL, 285 g, 4.60 mol) in one portion. The temperature of the resultant white slurry was found to rise slightly (~35 C). Stirring was continued
under ambient conditions for 1.0 h and then the precipitate was collected by filtration and washed in succession with distilled H2O (3 x 500 mL),
dilute aqueous NH3 (0.6 M*, 5 x 500 ml) and additional distilled H2O (5 x 500 mL). The filtrates were combined for disposal. The bright white solid
was allowed to air dry in preparation for calcining.
* Prepared by dilution of 103 mL 28% aqueous NH3 to a volume of 2.5 L with distilled H2O.
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