chironex
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Carbonate test for neutrons
Many years ago I was working on building a fusor and was interested in neutrons and more specifically, using them to "transmute" one element into
another. I like the idea of being able to take something normal and make it radioactive, and all the things you can do with that. Recently I had an
idea for an experiment.
Sodium exists almost entirely as sodium23. If you were to expose sodium to a strong neutron source (and ideally slow the neutrons down first to
increase chance of absorption), some neutrons should be absorbed and you should end up with stable magnesium24. So the experiment goes like this. Make
a concentrated solution of sodium carbonate, which should be clear. If you expose it to enough neutron radiation, some magnesium should form.
Magnesium carbonate however, isn't particularly soluble, especially not in an alkali solution. So it should precipitate out. If nothing else, the
solution should go cloudy after a while.
I feel like the easiest way to attempt this is with a "neutron oven" made of high density polyethylene and using a americium/beryllium or similar
neutron source. Let it cook for a few hours and see if it goes cloudy.
I have no idea if there's any practical purpose to this, frankly there probably isn't, but it's interesting all the same. Any thoughts on if would
work? Anyone with a neutron oven wanna give it a try?
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Maroboduus
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I believe the technical term for the number of slow neutrons needed to make that happen would be, "a shitload".
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j_sum1
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You might be able to improve this slightly by using potassium carbonate (which is more soluble than Na2CO3) and produce calcium carbonate (which is
less soluble than MgCO3). If you play the game close to saturation then it might just be possible to detect something. But it aint gonna be any kind
of cloud chamber. Nice idea but I fear not sensitive enough to be practical.
It is definitely worth doing some proper calculations to check feasibility. Maybe exposure to a strong source on the order of days is sufficient to
cause Raleigh scattering.
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wg48
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You probably don't want to be in the same room or even house of a neutron source that is powerful enough to transmute a quantity of an element
sufficient to detect with a precipitate.
Fortunately smoke detectors only contain about 1ug (rounding it up) of americium half of which will decay in about 400 years. So about 1/3,500,000 of
that 1ug of will decay per hour. That about 0.3ng. At 100% transmutation efficiencies of thats 0.03ng of sodium. More realistic efficiencies
apparently are less that 0.1% which rounding up again is 0,0003ng per hour ie 0.000,000,000,000,0003g per hour approximately give or take an order or
two..
That’s millions of times less than the impurities already present in a few grams of any sodium salt you have.
So its very very very impractical.
[Edited on 1-11-2016 by wg48]
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j_sum1
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Thanks for that wg48. I didn't have opportunity to think it through and crunch the numbers at the time I made my comment.
I think you have put this into perspective nicely.
A bit of a shame in a way. It was a novel concept.
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wg48
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Your welcome j sum.
Perhaps its surprising that radioactivity was detected more than 100 years ago. Fortunately there are more sensitive methods than the precipitation of
an insoluble transmuted element.
Radioactivity was first detected with silver halide film. Which can detect a single high-speed particle. Which means its detection limit is about 1yg
or 0.000,000,000,000,000,000,000,001g. It is even possible by eye to detect a single electron from the flash of light it makes hitting a florescent
screen and my favourite, Millikan’s oil drop experiment. That's detection of less than 0.001yg. Our technology and ingenuity is very impressive
considering we are only smart apes well ok very smart apes.
[Edited on 1-11-2016 by wg48]
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PHILOU Zrealone
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You should be dancing the Neutron dance (Beverlyhills cop movie)     
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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phlogiston
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Most methods for detecting the decay of single atoms rely on the fact that although a single particle is emitted, it has so much energy that it can
initiate many ionization events to yield a small but detectable signal, be it in the form of a flash of light, insulator breakdown, formation of
hole/mobile electron pairs, etc.
Your proposed method does not have that advantage. You need at least 1 neutron to form one atom of magnesium (and in practice you actually need many
neutrons for each atom of Mg).
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MrHomeScientist
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Perhaps another (extremely) long term experiment for woelen to try?
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careysub
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Quote: Originally posted by wg48  | Your welcome j sum.
Perhaps its surprising that radioactivity was detected more than 200 years ago. Fortunately there are more sensitive methods than the precipitation of
an insoluble transmuted element.
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The usual date given for this is February 1896 by Henri Becquerel, with the exposure of photographic film to a specimen of uranium salts, which is 120
years ago.
However Claude Niepce de Saint-Victor, a cousin of photographic pioneer Joseph Nicéphore Niepce, described his observations of this same phenomenon
to the Académie des Sciences in 1858 (158 years ago), but no notice was taken so he is not given credit.
About that which we cannot speak, we must remain silent.
-Wittgenstein
Some things can never be spoken
Some things cannot be pronounced
That word does not exist in any language
It will never be uttered by a human mouth
- The Talking Heads
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wg48
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Thanks careysub I have corrected my error.
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Maroboduus
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Sure, it's impractical, but I just wanted to point something out about this putative reaction that I missed at first.
You wouldn't get magnesium carbonate alone. You'd get magnesium hydroxide too.
There aren't enough carbonate ions to keep all that newly formed magnesium happy.
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Metacelsus
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You'd get beta particles (electrons) directly from the decay (and electron antineutrinos, but those don't matter here). If absorbed by the water, the
electrons would eventually generate hydroxide and hydrogen gas.
Another problem with the idea is that the water in the solution would probably absorb many more neutrons than the sodium. (This is based on a rough
comparison of the neutron absorption cross sections, and the fact that hydrogen atoms will be present at roughly 110 mol/L).
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phlogiston
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If you were to also saturate the solution with 235U-uranyl carbonate, the numbers of available neutrons could be amplified tremendously.
If the setup could be engineered to be in a barely subcritical configuration (amount of liquid, shape of the container), perhaps it might be possible
to generate a visible precipitate from a small number of initial neutrons.
The solution would probably be need to be kept under pressure to prevent sudden boiling from obscuring the precipitate.
[Edited on 2-11-2016 by phlogiston]
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wg48
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Metacelsus: I thought the blanket generated and moderated the neutrons from the beta. Don't you get the occasional neutron when an electron hits
something.
Phlogiston: A neutron reflector and perhaps a heavy water moderator would significantly reduce the size of a barely subcritical configuration and the
excess heat could be used to generator electricity not that you will need electricity for lighting because you will glow in the dark LOL
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Maroboduus
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| Quote: Originally posted by phlogiston | If you were to also saturate the solution with 235U-uranyl carbonate, the numbers of available neutrons could be amplified tremendously.
If the setup could be engineered to be in a barely subcritical configuration (amount of liquid, shape of the container), perhaps it might be possible
to generate a visible precipitate from a small number of initial neutrons.
The solution would probably be need to be kept under pressure to prevent sudden boiling from obscuring the precipitate.
[Edited on 2-11-2016 by phlogiston] |
Yeah, and if a frog had wings it wouldn't bump it's ass a hoppin'
If you just set off a large hydrogen bomb in the lab the neutron flux would be more than enough to make a precipitate, but cleaning up afterwards
would be a drag.
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wg48
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Maroboduus: Actually you would not need a large hydrogen bomb a small neutron bomb would do it more effectively. The clean up would be much less but
still very messy LOL.
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chironex
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| Quote: Originally posted by Maroboduus | Sure, it's impractical, but I just wanted to point something out about this putative reaction that I missed at first.
You wouldn't get magnesium carbonate alone. You'd get magnesium hydroxide too.
There aren't enough carbonate ions to keep all that newly formed magnesium happy. |
What if you had a supply of carbon dioxide bubbling through the solution? Would help tip it towards carbonate formation rather than hydroxide.
Thanks for all the responses. I realize this isn't practical at all and that silver halides would work better. If I was just going for detection I'd
use my nice helium 4 proportional tube XD. This is all more of a curiosity.
Ok so you'd need higher neutron flux, but in theory it could work? You probably wouldn't wanna be near anything capable of this reaction, but still
would be interesting to see what it would take to make it work. I like the idea of pressurized uranyl carbonate. Sounds exactly as dangerous and crazy
as I like my theoretical chemistry XD Rather than concentrated uranyl carbonate, maybe lower the concentration and add a small amount of beryllium
salt to the solution to increase the neutron count further. Beryllium carbonate is relatively soluble comparatively so it shouldn't crash out if you
use a small enough amount, but then you risk it not actually helping.
Alternatively could put the initial sodium or potassium solution in a neutron beam from a nuclear reactor, that ought to be plenty. Expensive, but
effective! And would probably be safer than pressurized uranyl carbonate
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Maroboduus
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Actually, the hydroxide is less soluble, so it would be a MORE sensitive test.
But 100 times more sensitive isn't gonna help much if you're at a trillionth of the threshold.
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unionised
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Adding uranium would complicate things a lot.
https://en.wikipedia.org/wiki/Spontaneous_fission
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phlogiston
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Hmm, very good point, it would.
Spontaneous fission (SF) can be considered a background signal against which the unknown neutron flux is to be measured. Both will be amplified by the
235U. The ratio of the neutron flux to be measured against the contribution of SF is relevant. A signal to background ratio of 1/10 is
often considered acceptable for quantitative measurements in analytical chemistry.
As a result of SF, the detection solution also cannot be kept for long periods of time, as SF will continuously generate neutrons and cause a MgCO3
precipitate to form after some time, even if no signal is present.
So, spontaneous fission imposes a limit on the neutron flux that can be detected with this method, which depends on many factors including the
isotopic purity of the uranium used.
Ofcourse, all of this is highly impractical and dangerous. It is just of academic interest.
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wg48
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There are heroic experiments that detect some particles with apparently improbable transmutation methods.
In the Homestake experiment they detected solar neutrinos using tons of dry cleaning fluid to get just about one transmutation per day of an atom of
chlorine.
Its not really comparable to detecting a precipitate as they used the decay of the transmuted chlorine for its detection but heroic never the less.
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careysub
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Since nuclear transformations involve a million times as much energy as a chemical transformation (as a rough guide) the quantity of product in any
laboratory experiment is roughly a million times smaller, total reaction energies being equal (though here too, nuclear reactions typically involve
much smaller amounts of energy so even a million fold reduction understates how large a reduction in product mass is involved).
Because of this any detection method must be one that it extremely sensitive, and typically has some large multiplication effect. So nuclear reaction
products are detected with radiation detectors that can measure individual particles due to cascade reactions. When these methods are chemical, they
are colorimetric - relying on the ability of optical observation to detect extremely small changes. The use of photographic film can be considered an
example of this.
If you want to chemically (i.e. not by radiation emission) detect a radiochemical you will need to use a reagent that forms chromophore complexes with
high absorption coefficients. The use of arsenazo reagents to detect trace amounts of actinides for example.
About that which we cannot speak, we must remain silent.
-Wittgenstein
Some things can never be spoken
Some things cannot be pronounced
That word does not exist in any language
It will never be uttered by a human mouth
- The Talking Heads
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chornedsnorkack
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Would there be any chemical reactions which:
1) are highly sensitive to fission tracks, but not to alpha particle tracks, and
2) cause not only passing flash, but a permanent colour change?
Silver halides amplify light effects - once developed. Not so much before. And the problem is, they are sensitive to light.
Silver halides are, as mentioned, sensitive to visible light. It is estimated that 3 to 4 photons are needed to form a latent image in one grain.
So, could there be any substance which, like silver halides, possesses amplification reaction of development, but which is completely insensitive to
visible and near-UV photons, and only forms latent/developing image under ionizing radiation of sufficient ion density?
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Stibnut
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As already mentioned, this won't work at any neutron flux you could get outside of a reactor. But it would be pretty cool to activate Na-23 and make
Na-24, which has a half-life of 16 hours and some interesting high-energy gamma decays.
However, its cross-section is only 0.53 barns. That's more than enough if you have a strong source, but I'm not sure if you could do it with an
amateur fusor. The folks at fusor.net seem to prefer silver and indium for activation tests.
Apparently one of the problems with the underwater Operation Crossroads nuclear tests was that copious amounts of Na-24 ended up everywhere. They had to wait several days for it to decay away
before trying to decontaminate all the non-sunk ships and counting how many of various animals onboard survived. They were still mostly unsuccessful
at decontamination even after it decayed because of all the normal fission products. Still though, except for the animal cruelty, old-timey nuclear
tests were really cool.
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