thorium228

Thorium-228 is a radioactive isotope of thorium with 90 protons and a mass number of 228. It is part of the natural thorium-232 decay series (the thorium series) and is formed within that chain when Ra-228 beta-decays to Ac-228 and Ac-228 beta-decays to Th-228, which then decays further to Ra-224. Its half-life is about 1.9 years.

Th-228 decays by alpha emission to radium-224, releasing energy typical of alpha decays. Because of its intermediate position in the thorium-232 series, Th-228 is produced and destroyed continuously in geological materials containing thorium and its decay products. The isotope is short-lived relative to many radionuclides in the series, which affects its presence in natural samples and its radiochemical behavior.

Occurrence and handling are tied to its role in the uranium-thorium decay chains. Th-228 occurs in trace amounts in thorium-bearing rocks and minerals as part of the decay process that ultimately leads to lead-208. In practical terms, its short half-life and alpha emission limit its use to specialized radiochemical and geochemical studies, where its production and decay can be exploited to investigate radionuclide migration, dating methods, or tracer experiments.

Safety considerations for Th-228 center on its alpha radiation. Although alpha particles have limited penetrating power, ingestion or inhalation of Th-228 or its progeny poses health risks due to internal irradiation. Proper containment and handling are essential in research and analytical settings.

See also: thorium-232 decay series, uranium decay chains.