Description: heavy artificial metal

Isotopes: itself an isotope of uranium

Production: irradiation of thorium 232

Use: usable, but little used in nuclear warheads and fuel

Radioactivity: emitter of relatively weak alpha particles and gamma radiation

Commentary: fissile substance; always present with uranium 232, the descendents of which are bismuth 212 and thallium 208

Uranium 233 is a synthetic isotope produced by the irradiation of thorium 232 (see the section Thorium)

Use

Like uranium 235, uranium 233 is fissile, and it is usable as fissile material in weapons and reactors. The critical mass of uranium 233 is less than that of uranium 235 and like that of plutonium 239 [Albright 93]. According to the NRDC, only a kilogram is needed to fabricate a nuclear device with a power of one kiloton [Cochran 94].

Today uranium 233 is found only in very small quantities in nuclear warheads, because it is more difficult and more expensive to produce than uranium 235 and plutonium 239. Moreover, it is more radioactive than uranium 235 and can complicate the construction of weapons. It can make nuclear weapons less reliable. But these characteristics would not stop uranium 233 from being used by people wanting to fabricate a nuclear device secretly. Therefore, it is on the list of the minister of industry.

For commercial purposes, uranium 233 has been used in high temperature reactors (HTR) (see Thorium).

Health

The chemical effects of uranium 233 are like those of other uranium isotopes and, like uranium 235 and 238, it is an alpha emitter. But it has a half life of 162,000 years, shorter than those of uranium 235 and 238 and a specific activity and a radiotoxicity greater than theirs.

Moreover, uranium 233 always contains a contaminant, uranium 232, the descendents of which, bismuth 212 and thallium 208, emit harsh gamma radiation.