Uranium-233

U233 is an unnatural Uranium isotope acquired by breeding Thorium. It is the fissile material used to make Thorium Fuel It itself can also be bred into U235.

Uses
Uranium and Thorium fuel.

Breeding U235.

Trivia

 * U233 is actually a fissile material, which means it can be used in nuclear fission weapons, even if it can't be in NTM.
 * This was tested in the United States nuclear test series Operation Teapot. This test was called "MET" (Military Effects Tower) and it used a U233-Plutonium core. It was considered a failure due to only reaching 1/3rd of its estimated yield, ruining many tests.