Uranium-233

So he drove his Pontiac behind a camping equipment store to buy some boxes of mantles from an employee that were conveniently missing from the store inventory.

His hope was to breed the Thorium-232 into Uranium-233, an excellent fissile fuel material.

The problem was, in that process it also produces byproducts that emit gamma radiation.

the most penetrating, and one of the most dangerous types of radiation.

I'm sure you're aware, sir, that I shouldn't be asking you questions unless this were a most important matter.

What's up? Someone run off with some U-233?

As a matter of fact, that's part of it, but not all, I'm sorry to say

sayNow look here, are you serious? If any U-233 had been missing, I should have known about it

You knew of none being missing?

I did not, nor do I know now, sir

Thankfully however, or unfortunately depending on your perspective, U-235 is not the only fissile isotope.

In general, most isotopes heavier than Actinium with an odd number of neutrons are fissile, with the most common nuclear fuels other than U-235 being Plutonium-239, Plutonium-241, and Uranium-233.

Plutonium-239 and U-241 can be bred in a nuclear reactor by bombarding common U-238 with neutrons.

When U-238 absorbs a neutron, it becomes Neptunium-239, which then decays via beta emission into Plutonium-239.