Americium-242

Americium-242

Americium-242m is a radioactive isotope of Americium with 95 protons and electrons and 147 neutrons and a mass of 242.0595492 g/mol. It has a half-life of approximately 141 years, decaying:
#99.54% of the time by isomeric transition (with a decay energy of 0.05MeV) to its short-lived nuclear isomer americium-242
#0.46% of the time by emitting an alpha particle (the decay energy is 5.64 MeV) to turn into Neptunium-238
#very rarely by spontaneous fission (halflife (9.5±3.5)×1011 years) [ [http://prola.aps.org/abstract/PR/v155/i4/p1309_1 Phys. Rev. 155 (1967): J. T. Caldwell, S. C. Fultz, C. D. Bowman, and R. W. Hoff - Spontaneous Fission Half-Life of ] ]

242mAm is fissile (because it has an odd number of neutrons) and has a low critical mass, comparable to that of plutonium-239. [http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/6.5_022.pdf] It has a very high cross section for fission, and if in a nuclear reactor is destroyed relatively quickly.

Another report claims that 242mAm has a much lower critical mass, can sustain a chain reaction even as a thin film, and could be used for a novel type of nuclear rocket. [ [http://www.sciencedaily.com/releases/2001/01/010103073253.htm Extremely Efficient Nuclear Fuel Could Take Man To Mars In Just Two Weeks ] ]

Americium-242 has a half-life of 16 hours. This is one of the rare cases when a lower-energy nuclear isomer is less stable than the higher-energy one. It decays: [ [http://www.matpack.de/Info/Nuclear/Nuclids/A/Am242.html 95-Am-242 ] ]
#82.70% of the time, by beta decay to curium-242
#17.30% of the time, by electron capture to plutonium-242

ee also

* Americium
* Isotopes of americium


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  • Curium 242 — Le Curium 242, noté 242Cm, est l isotope du Curium dont le nombre de masse est égal à 242 : son noyau atomique compte 96 protons et 146 neutrons avec un spin 0+ pour une masse atomique de 242,0588293 g/mol. Il est caractérisé par un… …   Wikipédia en Français

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