228Th

Thorium-228 (228Th) is a radioactive isotope of thorium with mass number 228 and atomic number 90. It is part of the thorium-232 decay series and appears as a daughter product in the decay sequence that includes 228Ac. 228Th has a half-life of about 1.9 years and decays principally by alpha emission to 224Ra.

Natural occurrence and production: In thorium-bearing materials, 228Th is produced within the thorium-232 decay chain as the sequence of decays proceeds from 232Th to its shorter-lived daughters. Because it is a member of a decay chain, 228Th is typically present in trace amounts in materials containing natural thorium, with activities linked to the levels of its parent and sibling nuclides.

Physical properties and safety: 228Th is an alpha emitter. Alpha radiation has high ionizing power but limited penetrating ability, so external shielding is usually sufficient, while ingestion or inhalation pose the primary radiological hazards. Handling, storage, and disposal require appropriate regulatory controls and containment to prevent internal exposure and environmental release.

Uses and regulatory status: 228Th is used in specialized research contexts, including calibration sources for alpha detectors and studies of thorium-series geochemistry. It can also serve as a progenitor for other short-lived isotopes within the decay chain in experimental setups. As a regulated radionuclide, its production, use, and disposal are subject to radiation safety and environmental protection regulations.