Americium242

Americium‑242 is an artificial isotope of the transuranic element americium. It has an atomic mass of 242 u and a nuclear charge of 95. The isotope was first produced in the early 1950s in nuclear research facilities by neutron irradiation of americium‑241 in a high‑flux reactor. It is typically created as an intermediate product during the neutron capture chain from ^241Am to ^243Am.

Americium‑242 is radioactive with a half‑life of approximately 4.9 minutes. It undergoes spontaneous fission with an average of about one fission event per 2,200 decays and emits neutrons, β− particles, and gamma rays. Its primary decay mode is prompt fission, which makes it a potential neutron source for research and commissioning of nuclear detectors. The isotope’s short half‑life and the difficulty of isolating it limit its practical applications; it is mostly observed in nuclear physics experiments and safety analyses of plutonium‑based weapons.

In the context of nuclear weapon physics, americium‑242 may appear in early-fission product chains in plutonium devices where delayed neutron production is considered. Its presence influences the delayed neutron fraction and thus the timing of criticality. Owing to its fissionable character, it can also contribute to neutron economy in certain advanced reactor concepts, though its production is not economically viable.

Overall, americium‑242 serves primarily as a subject of study in nuclear reaction dynamics rather than a material with extensive technological use. Its properties are documented in nuclear data tables, and it occasionally appears in the evaluation of fission product yields in isotope production.