thorium233

Thorium-233 is a radioactive isotope of thorium (chemical symbol Th, atomic number 90) with a mass number of 233. It is produced when thorium-232 absorbs a neutron, a process common in nuclear reactors and other neutron-rich environments. Because its half-life is short compared with many other isotopes, thorium-233 does not occur naturally in meaningful quantities and must be generated for any practical use.

The decay sequence of thorium-233 proceeds by beta emission to protactinium-233 (Pa-233), with a half-life of about 22 minutes. Pa-233 then beta decays to uranium-233 (U-233) with a half-life of roughly 27 days. This chain, Th-233 to Pa-233 to U-233, is central to the concept of the thorium fuel cycle, in which Th-232 is converted into fissile U-233 that can sustain a nuclear chain reaction in a reactor.

Applications and significance: Thorium-233 is an intermediate in the production of uranium-233, a fissile material that has been explored for use as nuclear fuel. The thorium fuel cycle aims to utilize thorium as an abundant precursor to U-233, offering potential benefits in fuel form, radiological safety, and spent fuel characteristics, though it faces technical and proliferation considerations comparable to other reactor fuels.

Safety and occurrence: As a radioactive isotope with beta and gamma-emitting decays, thorium-233 requires appropriate shielding and handling precautions. Its short half-life and limited natural occurrence mean it is encountered primarily in research or reactor environments rather than as a naturally mined substance.