241Am

Americium-241 (241Am) is a synthetic radioactive isotope of the actinide element americium (atomic number 95) with a mass number of 241. It is produced in nuclear reactors as a decay product of plutonium-241 and can also be generated in related fuel-cycle and reprocessing processes. In spent nuclear fuel, Pu-241 decays to Am-241, contributing to the radiological inventory of the material. Am-241 is not found naturally in significant quantities.

241Am decays primarily by alpha emission to neptunium-237, and has a half-life of about 432 years. In addition to alpha particles, its decay is accompanied by gamma radiation, most notably a low-energy gamma ray at 59.5 keV. The alpha particles have a very short range in air and most materials, so external exposure is typically limited, while internal exposure from inhalation or ingestion can be hazardous due to the long-lived radioactivity.

The dominant commercial use of Am-241 is as a compact, long-lived alpha source in ionization-type smoke detectors, where typically a sealed source containing roughly 0.9 microcurie (about 33 kilobecquerel) of Am-241 is incorporated. Am-241 is also employed in some industrial gauges, calibration sources for gamma-ray detectors, and certain research applications that require a stable, low-energy gamma emission and alpha radiation.

Safety and regulation for Am-241 sources are governed to minimize occupational and environmental exposure. Sealed sources are designed to limit leakage; mishandling or improper disposal can pose radiological risks. Long half-life and alpha emissions necessitate careful containment, licensing, monitoring, and proper disposal in accordance with applicable national and international regulations.