Convienient Deuturium Storage & Purification, ? Semi-Sealed Fusor

[lutzhoffman]

For those of us who do not have the luck of possessing a pressurized tank of D gas, this method of storage, and purification, may provide several attractive solutions. It would provide a handy method for storing D2 from an electrolytic cell also for example.Yes metallic depleted U is hard to get in the right form, but just a very small amount could provide enough for this application in short order. I have seen it on ebay many times in small amounts like this. Just 1 gram will hold almost 100ml of D gas, and at close to 20g/cc we are talking about a very tiny amount of depleted U. If the depleted U is not an option, then maybe Zr, Sc, or Ti could sub in? Depleted U seems better though, due to its almost ideal temp / pressure curve. It seems to be indicated from from the following, that U Deuteride could even be prepared between the reaction of D2O and metallic U, which is even more promising, provided that this reaction proceeds smoothly, and without the formation of the oxide in significant amounts. If this is true then no electrolytic cell would even be needed while enabling the use of cheap D2O, as a D2 source.

Here is a short excerpt from Wikipedia:

"Uranium metal heated to 250 to 300 °C (482 to 572 °F) reacts with hydrogen to form uranium hydride. Even higher temperatures will reversibly remove the hydrogen. This property makes uranium hydrides convenient starting materials to create reactive uranium powder along with various uranium carbide, nitride, and halide compounds.[2] Two crystal modifications of uranium hydride exist: an α form that is obtained at low temperatures and a β form that is created when the formation temperature is above 250 °C.[2]

Uranium hydride expands considerably during formation, and is therefore not an interstitial compound. In its lattice, each uranium atom is surrounded by 6 other uranium atoms and 12 atoms of hydrogen; each hydrogen atom occupies a large tetrahedral hole in the lattice.[3] The density of hydrogen in uranium hydride is approximately the same as in liquid water, or in liquid hydrogen.[4] The U-H-U linkage through a hydrogen atom is present in the structure.[5]

Hydrogen, deuterium and tritium can be purified by reacting with uranium, then thermally decomposing the resulting hydride/deuteride/tritide.[6] Extremely pure hydrogen has been prepared from beds of uranium hydride for decades.[7] Heating uranium hydride is a convenient way to introduce hydrogen into a vacuum system.[8]

The swelling and pulverization at uranium hydride synthesis can be used for preparation of very fine uranium metal if the powdered hydride is thermally decomposed.

Uranium hydride can be used for isotope separation of hydrogen, preparing uranium metal powder, and as a reducing agent.

Uranium hydride forms when uranium metal in e.g. Magnox fuel with corroded cladding gets exposed to water; the reaction proceeds as follows:

4 U + 6 H2O → 3 O2 + 4 UH3

The formed uranium hydride is pyrophoric; when the metal (e.g. a damaged fuel rod) gets exposed to air afterwards, a lot of heat may be generated and the bulk uranium metal itself can be ignited.[9] Hydride-contaminated uranium can be passivated by exposition to a gaseous mixture of 98% helium with 2% oxygen.[10] Condensed"

This got me thinking about the idea of a "Semi-Sealed Off Fusor?" with less than 100mg of depleted U for Deuterium storage, and also for pressure regulation at the same time. If you baked it out, or ion cleaned the inside wall, then it could work. Now you have a semi-sealed fusor containing a D loaded depleted U stub / insert. You could now control the fusor D pressure via the temperature of the stub / insert. Maybe someone else could offer an easier to obtain substitute for the tiny amount of DU, I do not know of anything which comes close when everything is considered. Attached is a PDF describing how they use this method for T gas, I am simply proposing that it should work just as well, with legal and safe D gas for fusor use .

PS: The small amount of DU could maybe even enable an internal fast neutron detection method, via the resulting U + Fast N fission reaction?

[Wilfried Heil]

You can get small metal hydride storage tanks with a nickel-vanadium alloy, for about the price of an empty lecture bottle. I am using one of these at the moment.

viewtopic.php?f=6&t=2592#p12102

The advantage is that the hydrogen is stored at low pressure and is released slowly, even in the event of a leak. The hydrides are spoiled by air or water vapor.

"Uranium beds" are used to store tritium and need a fairly high temperature to release it again. Anything but hydrogen or noble gases will be chemically gettered.

>PS: The small amount of DU could maybe even enable an internal fast neutron detection method, via the resulting U + Fast N fission reaction?
In principle, yes, at very high neutron flux untypical for a fusor. These are very insensitive to neutrons and entirely blind to gamma rays. Have a look at the cross sections for fast U-238 fission.

[Doug Coulter]

I have a few LARGE D2 thytratons here (from SLAC). They use a zirconium reservoir, I don't get the idea you hold all that much in it, but for these it's nice to give control over the tube pressure. They have a heater in there, and the data sheet tells how to monitor the tube pressure and adjust the heat for proper operation.

Lithium hydride is prettty stable too. I hear it's good to keep Li out of the system though.

I did play a bit with Pd as a heated diapraghm. I just didn't get enough D through it to be useful, that system wants a pretty big pressure drop for any flow to happen. We also have a hydrogen purifier working on the same principles for which the instruction manual was enlightening. Though much bigger than the one I'd made, it still had almost no flow through it at one atmosphere drop.

This kind of stuff is nice in a sealed off system, where all outgassing is over with and you only need a little. Most fusors can't run on that little amount of gas. Here, where I've tried (pretty hard) to run minimum gas flow and pumping, I still use up the amount of D in the pipe between the tank and regulator in about half an hour or so. It's at 400 psi there and about a CC of volume? That's a fair amount of gas.

Looks to me like you'd have to go to electron tube manufacturing techniques and materials to get the outgassing down to a point where you could seal the thing off, or nearly. This really restricts the materials you can use, and they do a real serious bakeout to get there. They bake to the point where the glass is about to collapse, and sometimes even do it in a vacuum tank around the tube to get things hotter than that without collapse from outside air pressure. Those guys have really refined technique, or did when they existed. This isn't impossible of duplication, but I don't think a big SS tank is ever going to satisfy that.

[lutzhoffman]

Hello:

Ya I get the point unless the whole thing is glass / metal seals it would be a bear to clean well enough for it to be stable in the long haul. Even laser tubes which are cleaned with fuming HNO3 before baking still get contaminated at times. I do like the idea from Wilfried on the tiny hydride storage bottles. Maybe you could home brew a bottle like this with some U in a small SS mini tank. This way you could keep the U in D2 or inert gas when not in use.

As far as the temperature goes I still like the U storage material much better than the commercial hydride storage stuff. With the commercial stuff you need a lot of pressure to charge it, with U you can charge it even in a vacuum! Also the gas release rate is very even, with no pressure regulator being needed. The release temp. of 250-300C is not hard to do, especially with insulation, and it a small price to pay for being able to suck it up under even rough vacuum condition's, and for doing away with the pressure regulator.

This way with a U hydride storage bottle you can now charge your bottle from a low pressure electrolytic unit, or even by passing D2O vapor through hot Mg turnings, which also suck up any residual N2 along the way, to make it even more attractive. So I may now shoot for making my own U metal hydride storage bottle, it would also be nice and compact for in terminal use.

Check out the Mg + D2O + Heat = D2 + MgO reaction, with the D2O in the form of D2O steam. The setup is the same one used for making MgN for the lab synthesis of ammonia, by adding it to water later. Very easy and safe when compared to the use of many more reactive metals. Plus there is a big rod with over a pound of Mg, in almost every tank type of water heater, so its free : )

It may be interesting to mount 2 of these U hydride bottles at different points in an ion source. This way the hot one supplies the D2 for the source, and the second cold one acts as a getter pump, which is selective to D2, to lower the accelerator tube gas load, by re-absorbing a good portion of the D2 streaming from the source towards the accelerator tube.

Take Care....Lutz

[Doug Coulter]

They use zirconium in industry, because it works better and is cheaper.
Hint!