Fusor Forums

I work with rhodium refining and see it in powder form constantly, I had an idea about pressing it in a pellet for maximizing the surface area and be capable of using minute quantities in an activation target.

The advantages would be the minimum quantity required to make a pellet (~1g), and as it is mixed with polyethylene wax, the wax possibly can serve as a moderator to increase the activation rate.

To test the idea I made a silver powder pellet.
The silver powder is mixed with the polyethylene wax, spread on the mold, boric acid is added on top of it and it's pressed with 20 tons, here's the resulting pellet:
What do you guys think?

Your work seems very promising to me.

But what purpose is served by the boric acid?
Does it improve the mechanical properties of powdered metal pellets,
or have another use in the pressed-pellet business?
I think it's bad to have boron anywhere close to where you want lots of thermal neutrons.

Since you now have a pellet of Ag and polyethylene and boric acid,
is the next step to compare its activation with similar weight of plain silver metal?

My guess is it's a flux but that implies sintering, which OP didn't mention doing.

The purpose of the boric acid is mechanical structure, because otherwise the pellet would be too thin and frail as only 1g of silver is present, the boric acid is used only in the back, the front silvery face is pure silver+wax.

Since silver is cheap, the pellet can be 100% Ag+wax, also if the boric acid in the back interferes it can be changed to starch, but that makes the pellet powdery and no plastic like when using H3BO3.

It's not sintered, all process is cold.

The quantity of wax can be increased if found to be usefull.

This is a cool idea, but the boric acid is self defeating because of the massive cross section of B 10.

Activation is normally done best by surrounding the target with neutrons. Dont think that all the business is done by neutrons coming from the source direction. This is why Richard's "neutron oven" has HDPE surrounding the target. Neutrons will scatter back from the moderator.

I have a friend who wisely bought 1 ounce of Rhodium in an ingot over a year and half ago for ~$800. Now, it is through the roof!! ($5,000+/try oz.) Rhodium is traditionally all over the place in price. He brought it over and we exposed it to fusor neutrons. Rhodium only takes about 5 minutes and it is as radioactive as it will get in the given flux within a given moderator! I loved it! Best stuff there is to activate. Second best is silver. The activation product of choice in limited flux systems is thin metal foil and nothing else. Rhodium was a favorite of Enrico Fermi back in the late 30's

In a reactor with a monster flux, a chemical of the activation material is the material of choice. A compound with a molecule of many atoms of what you wish to activate is chosen with the other elemental component being of such a tremendously long half-life that it would not intrude into the desired radiation or of so short a half-life that a day or even a month would see it decay out of the picture, leaving only the desired decay radiation present. To complicate the decision, water solubility of the irradiated compound might be either highly desirable or, on the other hand, totally insoluble in common reagents.

Activation at the fusor level of production achieved by the average amateur would, ideally, demand a foil of Silver, Indium or Rhodium. Having a rolling mill, I have foils of indium and silver on hand at the fusor for demo.

Richard Hull

Just made 2x 40 mm diameter circles of silver metal, one with 10,38 g and ~0,80 mm thick and another with 2,76 g and 0,25 mm thick.

I will make a 40 mm pellet of PE wax with 2,76 g of silver powder and compare it with the solid metal disc, this way I can experiment without using rhodium.

Great work! Silver is by far the #1 choice used here by fusioneers looking to do activation due to costs and availability.

Richard Hull