I just wanted to say how happy I was to learn that David Hahn’s homemade nuclear reactor involved the use of duct tape.
I mean, how else would you build one?
I remember a follow-up article I read about David Hahn. After his little escapade with his back-yard Chernoybl, he joined the United States Navy as a nuclear technician. Pretty interesting, albeit shortsighted, kid/guy.
For an impromptu camping trip in the Blue Ridge Mountains of Virginia, I bought an “Ozark Trail” lantern from Wal-mart (Made in China, natch…).
Came with a warning:
*IMPORTANT In normal usage, these mantles are quite safe but they contain and emit small amounts of naturally radioactive materials whether lit or unlit. In view of public concern about exposure to radiation of any type, Wenzel recommends following the directions, below:
Avoid carrying mantles close to the body, whether in packages or not, for extended periods or handling mantles more than necessary. Whether in packages or not, wash hands after handling.*
{ lots more; essentially: do not lick mantles, rub mantles on skin, breath ash, sniff ash, rub ash in eyes, etc… }
and this one:
This product contains a chemical known to the state of California to cause cancer
Californium? 
Butane: C3 H8
Yttrium: Y
:waves firebrick edit wand:
Propane : C3 H8
Butane : C4 H10
<hank hill>
Butane is a bastard gas!
</hank>
They’re being too paranoid when they warn you against mantles in the package, thorium being an alpha source. But you definitely don’t want to lick it.
Do not taunt Happy Fun Lantern.
Thorium is one of the fissionable elements. Do you suppose we might see a Wal-Mart distribution center disappear in a mushroom cloud someday if they stack too many crates of thorium mantles together and it goes critical?
Regards,
Sky
One can only hope.
I strongly doubt that the most common isotope of thorium, with a half-life of billions of years, is fissionable. Concerns about a Wal-Mart distribution center going critical are probably less justified than similar concerns for a FiestaWare distribution center.
It was a joke son, just a joke.
Best,
Sky
Half-life and fissionability are not all that closely related. The half-life of U-235 is 704 million years.
Thorium-232 is both the commonest isotope and is fissionable. The reason this tends to be overlooked is that the reaction doesn’t produce enough neutrons to sustain a chain reaction. Bit dull really.
That some form of thorium was fissionable was realised very early on - one of Hahn and Strassman’s followup papers established it in 1939.
I’m pretty sure that thorium 232 is NOT fissionable… and a cursory look at that link seems to back it up.
It can be converted into fissionable U-233, if memory serves me correctly… but you have to bombard it with neutrons just to get it to that stage, right??
The n_TOF collaboration is currently measuring thorium cross sections at CERN. Figure 2-2 in one of their proposals summarises the previous data on fission cross sections for Th-232. It doesn’t fission with slow neutrons, but there’s a threshold at about an MeV and above that the cross section’s on the order of 0.1 barn.
Being pedantic, it’s not fissile, but it is fissionable and easily so.
Thorium-232 can be converted to U-233 in a breeder just as U-238 can be converted to Np-239 (which spontaneously converts to Pu-239).