Sciencemadness Discussion Board - Radioactive Boyscout

Radioactive Boyscout

Darkfire - 25-11-2003 at 22:59

Well we all know the story, but i think i wanna try something like it as my spring project for chemistry,

A small sample of an alpha emiter would shoot a beam of alpha particals, passing these through Be would toss out nuetrons which would then be slowed, before entering the sample of Thorium. The thorium would then decay to Ac ( http://chemlab.pc.maricopa.edu/periodic/Th.html ) which would futher decay into Uranium ( http://chemlab.pc.maricopa.edu/periodic/Pa.html ), after due time in the nuetron beam the sample would be checked for the presents of Uranium ( http://unitednuclear.com/testkit.htm )

Is this even possible?

I've seen alot of problems so far like getting the Be, Th, and alpha emiter but if i try hard they should come, what do you think about this idea?

~H

[Edited on 26-11-2003 by Darkfire]

Marvin - 27-11-2003 at 00:30

The alpha source in a smoke detector being slightly less than 1uCi would give you in the region of 1 neutron per second completely mixed with Be. This essentially isnt detectable and it certainly isnt preperativly useful. The kind of alphas you need for decent neutron production are... extremely dangerous. Be isnt a problem as you can use Boron instead but the very low alpha to neutron conversion rate of both (and these are the best) is just too low.

Better home sources can be built for neutrons as Ive mentioned in E&W. They arnt easy but they do get you enough for decent experiments and they dont require any licenced chemicals or radioactive elements.

You wouldnt be able to make enough to affect the test kit even with a neutron source strong enough to kill you in an hour, and which is rather overpriced considering its just based on borax beads a lighter and a near UV LED.

In any case, Thorium allready contains uranium as a daughter product, just like uranium allready contains thorium. Even if you purified the sample beforehand youd have to work *very* hard to exceed the rate of production of uranium by simple decay.

If you can get some uranium acetate or nitrate and a teacher mad enough to let you play with it theres a trick you can do. I'll have to look up the details, but you add a coprecipitant and boil with alkali and all the thorium ppts out as hydroxide. Result, solution is now 'dead' to most geiger counters (alpha only, and feebly radioactive at that), while the ppt has all the beta/gamma activity in the sample and that decays (and the U salt regains) over a few months.

Darkfire - 27-11-2003 at 10:56

Thanks, i new it wouldnt work out...

edit: Can you link me to that page on E & W?

~H

[Edited on 27-11-2003 by Darkfire]

Nevermore - 27-11-2003 at 13:05

Quote:

Originally posted by Darkfire
Well we all know the story, but i think i wanna try something like it as my spring project for chemistry,

A small sample of an alpha emiter would shoot a beam of alpha particals, passing these through Be would toss out nuetrons which would then be slowed, before entering the sample of Thorium. The thorium would then decay to Ac ( http://chemlab.pc.maricopa.edu/periodic/Th.html ) which would futher decay into Uranium ( http://chemlab.pc.maricopa.edu/periodic/Pa.html ), after due time in the nuetron beam the sample would be checked for the presents of Uranium ( http://unitednuclear.com/testkit.htm )

Is this even possible?

I've seen alot of problems so far like getting the Be, Th, and alpha emiter but if i try hard they should come, what do you think about this idea?

~H

[Edited on 26-11-2003 by Darkfire]

Well, this is my field so i can tell you something about that...
getting an alpha emitter is not a big problem, just care that the alpha particles have enough energy, i suppose at least 3MeV to be able to travel enough to enter the Be and toss out one neutron.
Care must be taken since berillium powder is toxic, getting berillium pure nuclear grade will be a big deal..
You can't slow the neutrons before sending into Th, for two reasons, 1) if you slow by hydrogenated matter they will be likely absorbed by the hydrogen, if you use graphite, they will be easily absorbed too, heavy water is the best choice, but is not OTC usually..
2) do you know how small is the cross section of Th for fast or thermal neutrons? this is not a chemical reaction, you need FAAAAAR excess neutrons for some results to be seen...
How will you check for uranium? with spectroscopical methods, since even if you use a very strong neutron field you will get only a few U atoms.
Not considering that exposing yourself to a field of neutrons could degrade your life quality

for me is definitely out of the normal possibilities of anyone.

Darkfire - 27-11-2003 at 15:49

Ive come to realize that...

~H

Iv4 - 28-11-2003 at 05:43

Could an H laser pull it of?Just curious since I tried something like tat once.Two metres 1cm thick tube(AL) at .5 torr refused to lase.Etiehr that or it did and I had no way of checking.

You'd have better luck trying to extract the U from glass IMHO.

BromicAcid - 28-11-2003 at 09:58

Quote:

heavy water is the best choice, but is not OTC usually..

If you want some heavy water, not much but some, preferably get some distilled water and start electrolyzing it. Heavy water makes up a small but measurable percentage of normal water and heavy water takes a higher voltage to degrade to hydrogen and oxygen. If electrolyses is continued on a large quantity of water the final several milliliters will consist of quite concentrated heavy water.

Nevermore - 29-11-2003 at 01:39

well considering in which percentage is D2O in normal H2O i'd have to electrolyze for some LOOOOONG time to get a reasonable amount of D2O, the problem is, that if even a % of H2O is inside, the bitch will eat the neutrons like candies. If i remember good the normal difference between H2O and D2O is mV and the big prob is that it changes with temp!

@iv4, a laser cannot pull out a neutron, there is a reaction where a radiation frees a neutron, but it happens only when you are using high energy radiations for example hard gamma rays (v,n). the probability of this reaction to happens is very small, for getting out neutrons efficiently you should use a spallation reaction, where and high powered and high current proton flow hits a target made of heavy mass elements, when the proton hits the nuclei a neutron can be spit out. Big problems: having a proton accelerator of sufficient power, having a very efficient vaccum source, having enogh electric power to make it work...

???

Hermes_Trismegistus - 29-11-2003 at 02:17

I am out of my league here and know it, but..

Would X-rays as an energy source help you here at all?

Just curious because I happened across an inexpensive home shop built powerful X_RAY emitter.

A souped up form of Crookes tube and I have been wondering about some other use for it, other than reliving Roentgens famous experiments

I was wondering if using the xrays to slap off electrons (as in common x-ray fluorescence) from isolated/grouped heliums and using the resulting pos charge to fling them out at your target might be feasible?

of course, remember I am just a lowly amateur so try to contain your wrath from having to read such an obviously silly suggestion

unionised - 29-11-2003 at 03:56

It's relatively easy to knock the electrons off helium. The difficult bit is accelerating them to a few MeV to get them to knock neutrons out of Be.
If you build yourself a powerful Xray source, be careful not to zap yourself (or anyone else).
The electrolysis for enriching deuterium has a problem. The voltage required to free hydrogen (as the gas) rises as the concentration of H2O (rather than D2O) in the solution falls. At some point it will reach the decomposition voltage for D2O. Then the outgoing gas will have the same ratio of H to D as the liquid that is left.
It makes a good start on getting D2O but it will never remove the last of the H.

Nevermore - 29-11-2003 at 04:34

using electrons to knock off neutrons is not possible with a minimum efficience, hence using an accelerated electron source is not good.
X-Ray won't be enuf, you will need gamma rays for knockin out neutrons..a few MeV should be enough.
D2O and H2O won't reach an eutectic like state, but the difference of voltage will progressively reduce so it will be more and more hard to separate H2O.
the difference will approx 0 as the H2O conc approx 0.

unionised - 29-11-2003 at 07:15

Sorry, didn't make myself clear. Accelerating the He ions left after doing the easy bit (ie ionising the He) up to MeV is the tricky bit.
The difference tends to zero for a H2O concn of zero. That's the same as saying you can't lose the last of the H2O.

Nevermore - 29-11-2003 at 07:47

UHmmm He ions are alpha particles..
so what's the point of using He if you can use an alpha emitter? =)

Iv4 - 29-11-2003 at 08:16

Yea I thought so but I was read(from a very unreliable source though)that the H laser emits H nuclei.Whatevr its freq is I could get it to work *shame*

Hermes_Trismegistus - 29-11-2003 at 12:25

I thought that was one of your linchpin problems?

Securing a serious alpha source?

Quote "The alpha source in a smoke detector being slightly less than 1uCi would give you in the region of 1 neutron per second completely mixed with Be. This essentially isnt detectable and it certainly isnt preperativly useful."

Nevermore - 29-11-2003 at 14:39

no a laser for definition emits only light, or coherent radiation.
not matter, if yes is not a laser but is a particle accelerator.
if you make an accelerating device in a hydrogen atmosfere then you will get protons and electrons at the anode and catode, if you use He you will get electrons and He nuclei, and so on. i don't know if i am clear enough but i dun wanna bore with long descriptions.

@smoke detectors: i knew they have an infrared light diode that is reflected all around a lot of small mirrors, when smoke enters the chamber the light is absorbed so the alarm triggered, i never heard of alpha emitter smoke det. Why? Alpha particles have very small path, in normal atmosphere they can travel not farther than 1-2cm...they can travel in human skin for no more than 7 microns...

unionised - 30-11-2003 at 04:01

I can generate billions of He nuclei per second using a discharge lamp. I can't get an alpha source that strong. That's the advantage to using some non-nuclear source of helium nuclei. The down side is that they aren't any use because they are not moving fast enough.

There will certainly be H atoms and nuclei free in a H laser. The point is that they stay in the laser (or are swept out if it's a flow system; they soon recombine anyway). Virtually none of them will have the sort of energy you need to do nuclear physics.

Most smoke detectors these days (at least the ones I have seen) use an alpha source to ionise the air. They then put a voltage accross 2 plates in the ionsed air and get a current. If any smoke particles get in they stick to the ions and slow them down. The current falls and the alarm goes off.

Marvin - 30-11-2003 at 23:20

unionised, re electrolysis explanation. No.
If protium and deuterium had significantly different oxidation potentials, they would behave like different elements. The differences in electronic energy levels between isotopes even in hydrogen are miniscule and far too small to affect electrolysis.

Two main things make electrolysis work well for enriching deuterium. Firstly because protium is lighter and moves faster at a given temperature it tends to react faster, so its preferentially reduced by the cathode. Secondly, if you setup an equilibrium between hydrogen and water (simply mixing them is not enough, you need a catalyst for interconversion of the H atoms) the gas phase hydrogen contains a lower proportion of deuterium that does the liquid phase. This sounds strange at first, that the 'static' concentrations should depend on the mass of a molecule, but when you remeber that equilibrium happens not when the reaction stops, but when the rate of the forward reaction is equal to the rate of the back reaction, and since these both depend on the mass of the molecules you get a difference between isotope concentrations. For enrichment of common water this second effect amounts to about 6 fold and soley was the basis of the german method of heavy water production. Over all for a single stage of ordinary water the enrichement factor is up to about 12 for single stage electrolysis in a well designed cell.

So long as you are not constantly diluting the water (say by topping it up from the tap as the volume decreases), you can reach any concentration you like with a single stage electrolysis cell, as the gas coming off will always be of a lower deuterium content than the liquid left behind. At a particular stage in the reaction though the gas coming off will have a greater concentration of deuterium than will the source water and it becomes profitable to burn this for a subsiquent run. Sodium hydroxide electrolyte and nickel electrodes are supposed to provide good results, though you will need to electrolyse of the order of 20 litres of water down to 1cc for a half decent amount of reasonable purity D2O. (from memory, I dont have the numbers to hand).

Practically, after 10-20% D2O has been reached its normal to use fractional distillation to furthur enrich, as this works out cheaper. This D2O will be expensive, and far too much to use as a moderator, for that youd need gallons at a cost of 10's of thousands in electric bills. A few cc's of D2O however has much better uses. Deuterium gas and oxide is itself unrestricted provided it is below nuclear grade, and ranges from typically 10c to $1/gram, less than it would typically cost to manufacture with domestic price electricity.

Making the alpha radiation yourself would be difficult, youd need 4Mev or so and thats a linac or utterly massive drift tube accelerator, essentially unfeasable at home. Photons arnt a bad idea, but to make those you need high energy electrons. 10Mev electrons going into something like a tungstun target will get you photons with a mean energy of about 2.5Mev. Surround this target with deuterium or berylium and the photoelectric effect, yes quite literally, will get you neutrons. Making 10Mev electrons though is esentially linear accelerator only and that means microwave engineering. Spallation is the way the big boys do it, but this requires proton energies of the order of several hundred Mev and its strictly fantasy stuff for a home experimentor.

While I'm mentioning 'photons' I'll point out that the difference between gamma rays and x rays actually has nothing to do with energy. Its perfectly possible to have an X ray photon with more energy than a gamma ray photon. The difference is that X rays result from changes in the electronic structure (usually the inner shells) of atoms, whereas gamma rays result from nuclear events. The 2.5Mev photons from the accelerator would be called bremsstrahlung.

The most feasable method for home neutron production is fusion. Fuse deuterium nuclei and in fractionally less than 50% of successful reactions you get a helium 3 nucleus and a 2.5Mev (ish) neutron as the product. For a decent chance of a reaction you only need 200kev which you can get with a drift tube accelerator and a van der graaf electrostatic type machine (up to about 10ua). For higher currents a cockroft walten voltage ladder should work well for around 1-2ma and potentially getting you of the order of 10^9 n/sec for 200W odd power. Rather a better use for deuterium, I feel, part of which needs to be in the target and part as a gas in the tube at very very low pressure.

The only semisane alternative to drift tube fusion is the farnsworth fusor, which generally operates at much higher currents, but at only about 20kv in a simpler enclosure. It achieves an order of magnetude or two less neutrons per watt of power applied compaired to the drift tube though. Something that casts rather considerable doubt on them ever breaking even.

These systems produce easily enough neutrons to make isotopes and the componants are entirly unrestricted. For most experiments a parrafin wax moderator should be fine, but for making fissionable isotopes, youd need something rather better, very pure graphite might do. Unfortunatly, nothing barring a mass spec would be able to detect these long halflife isotopes in the amouts youd be able to make them in. If you want to turn stable isotopes into short halflife radioisotopes however, you can very easily detect these with a geiger counter.

Iv4 - 1-12-2003 at 01:32

I ran some more more searches and it looks like only the best 3 metre long resonaters can extract 0.01 efficiancy out of it.Maybe it's bull but either way I'll look into it more.

Just theoreticaly how about an explosive pumping of H?Maybe like in a flux compresion generator.The imense power that could be derived from say a kilo of TNP might be enough.

Gamma rays compared to X-rays

Mr. Wizard - 1-12-2003 at 10:29

Marvin,
I enjoyed your explaination of the various methods of D2O production and the Alpha sources. I don't understand the distinction of X-rays vs Gamma, where the X-rays could be more powerful (read higher energy in electron volts) than Gamma rays. I always thought the x-rays lay in a continuum of energy levels from hard UV through to gamma? Maybe I don't understand? I realize most gamma radiation is from nuclear as opposed to electron clouds, but they are both photons or electromagnetic radiation, right?

BromicAcid - 1-12-2003 at 11:21

I found some of the specific information on the concentration of heavy water by electolysis:

Taken from Descriptive Inorganic Chemistry (third edition; Geoff Rayner-Canham; Tina Overton):

Quote:

The covalent bonds of deuterium and tritium with other elements are also stronger then those of common hydrogen. For example, when water is electrolyzed to give hydrogen gas and oxygen gas, it is the O-H covalent bonds that are broken more readily then the O-D bonds. As a result, the remaining liquid contains a higher proportion of "heavy" water, deuterium oxide. When 30L of water is electrolyzed down to a volume of 1 ml, the remaining liquid is about 99 percent pure deuterium oxide.

With all the energy required I would hardly consider this the cost effective method.

unionised - 1-12-2003 at 13:52

OK,I accept that repeated electrolysis will get you there; very expensively.
A lot of the production of D2O is now done using the H2O vs H2S exchange.
As for the electrode potentials
http://ptcl.chem.ox.ac.uk/~rkt/tutorials/emf/emf.html
It seems to be first year chemistry that they differ.

energy recovery

Mr. Wizard - 1-12-2003 at 14:45

Although it would be energy intensive to electrolyse 30 liters of water to get 1 ml of D2O, you could recover some of the energy by feeding the hydrogen and oxygen to a simple fuel cells (battery) to help power the electrolysis. It wouldn't get it all back due to resistance losses and other things, but it would help offset the energy cost. Isn't the efficiency of hydrogen oxygen fuel cells in the high 90s?
Just thinking out loud :-)

protium, deuterium and tritium

Tamzel - 30-7-2004 at 05:04

What is the difference between protium, deuterium and tritium?

Reverend Necroticus Rex - 30-7-2004 at 08:48

Protium is ordinary hydrogen, 1H,
Deuterium is heavy hydrogen or 2H and is used to make heavy water, and for experiments in fusion.

Tritium is 3H, heavier still than deuterium, radioactive with a half life of ten years ish and is used to make some watch dials glow.

Also, I once heard a passing mention, but only that, of two isotopes of hydrogen, 4 and 5H, but I unfortunately know next to nothing other that what logic dictates about them.

Marvin - 30-7-2004 at 11:43

Mr. Wizard,

X rays result from electron transitions, gamma rays result from nuclear transitions.

You can get high energy X rays and low energy gamma. It all depends on circumstances.