[r3dxmaverick]

So I have watched a scout boy make a nuclear reactor at home and I am wondering if its possible? And is it true that in a nuclear reactor thorium can become uranium and plutonium? thank you

[Arkcon]

The is a well worn story, and its a common topic on these boards.  Theoretically, it is possible.  However, the absolute facts of the story, I find, are a little bit sketchy.  There was a through treatment of the facts in Harper's Magazine -- and they were missing some, the boy  in question, and his family, were able to destroy some of the specific evidence before the NRC arrived.  Besides which, because of the terror risk, the specifics aren't often discussed.

http://www.chemicalforums.com/index.php?topic=7041.0

http://www.chemicalforums.com/index.php?topic=9715.0

http://www.chemicalforums.com/index.php?topic=17833.0

http://www.chemicalforums.com/index.php?topic=27520.0

[gippgig]

Yes, you can make a REAL nuclear reactor at home, but it would be totally different from the type people usually think of - an accelerator-driven sub-critical reactor. Instead of producing a self-sustaining chain reaction in a critical mass of fissionable material, an accelerator-driven reactor uses a high-energy particle beam to split target (i.e., U or Th) atoms generating a spray of neutrons that can cause additional fissions or breed fissile material. You would need a fairly high-energy particle accelerator and a piece of U or Th ore. Just aim the beam at the rock and off you go. Warning: While there is absolutely no danger of a meltdown with such a small system it would produce some really nasty things like ²³⁸Pu or ²³²U. Unless you have the knowledge and equipment to safely handle this stuff don't run the reactor for more than a few seconds.

[Enthalpy]

Ahum.

The particle accelerator isn't really easy to build at home.

The sub-critical reactor has never been built - neither at home nor outside. All designs need plutonium to work and a careful adjustment of the criticity (through the proportion of plutonium) to 99% to obtain perhaps more energy than is invested in the accelerator. In fact, nobody knows if it could work, and some serious arguments tell it's useless.

At home, you better make a fusor, or use a needle to produce the hydrogen-accelerating field.

[gippgig]

I'm not talking about breaking even or even producing a measurable amount of energy; a home reactor would just make some atoms fission producing neutrons that would cause a few more fissions (not even remotely close to criticality).
If you use a proton beam I think the energy required would be tens of MeV (to overcome the coulomb barrier) which would indeed require a hard-to-build accelerator. However, it might be possible to use a much lower-energy deuteron beam - I believe that when deuterons hit a light target a significant number break apart producing a neutron beam. A fairly simple Van de Graaff generator might be sufficient.

[Enthalpy]

I'm not talking about breaking even or even producing a measurable amount of energy; a home reactor would just make some atoms fission producing neutrons that would cause a few more fissions (not even remotely close to criticality).

Well, if you wish to call that a reactor... Take some uranium ore, grind it, mix it with beryllium powder. Alpha particles from uranium will expel neutrons from beryllium which will be absorbed by other uranium atoms, some of them will fission. O good. Easier in the backyard than an accelerator.

[Enthalpy]

So I have watched a scout boy make a nuclear reactor at home and I am wondering if its possible?

It wasn't a reactor, and I doubt he would have achieved one had he had more time.

And is it true that in a nuclear reactor thorium can become uranium and plutonium?

Thorium (of which only the isotope 232 exists naturally) can absorb a neutron produced by a reactor and become uranium-232 which is fissile. It won't get to plutonium because more neutrons cause 233-U (and the subsequent steps) to split instead of absorb more neutrons. 239-Pu and 240-Pu are made from 238-U absorbing neutrons.

A common desire is to consume the abundent thorium in a reactor, but this is more difficult than consuming 238-U and has never been done in a scaleable way. One proposal is Rubbia's amplificator, which is nearly-critical and driven by an accelerator, BUT:
- Near-criticality is precisely adjusted to 0.99 by the proportion of 239-Pu mixed with thorium... If it shifts by 0.01 for some reason, boom. And less than 0.99 makes the accelerator definitely impossible (many people say: at 0.99 already).
- Plutonium is yuk anyway, and the initial load allows to make bombs easily, so you can't export it.
- A thorium reactor needs Pu to start, not 233-U, and it doesn't regenerate this Pu. So it's NOT a real breeder, and will always need TEN uranium reactors to provide the initial plutonium to start one thorium reactor. This won't consume much thorium.
- Sure, getting rid of plutonium would be nice, but the same is achieved in a water-moderated uranium reactor. With MOx they burn plutonium together with less-enriched uranium, and in Russia (one US company tries it as well) a few reactors have burnt plutonium mixed with thorium. No breeders since they consume more plutonium than they produce uranium, but they use some abundent thorium instead of uranium.

If you sum it up: useless.