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With its half-life of 432.2 years, the americium in a smoke detector decreases and includes about 3% neptunium after 19 years, and about 5% after 32 years. The amount of americium in a typical new smoke detector is 0.29 micrograms (4.5 × 10 −6 grains) (about 1/3000 the weight of a small grain of sand) with an activity of 1 microcurie (37 kBq ...
Americium-241, an alpha emitter, is used in smoke detectors. The alpha particles ionize air in an open ion chamber and a small current flows through the ionized air. Smoke particles from the fire that enter the chamber reduce the current, triggering the smoke detector's alarm. Radium-223 is also an alpha emitter. It is used in the treatment of ...
Alpha particle radiation, as opposed to beta (electron) and gamma (electromagnetic) radiation, is used for two reasons: the alpha particles can ionize enough air to make a detectable current; and they have low penetrative power, meaning they will be stopped, safely, by the air or the plastic shell of the smoke detector. During the alpha decay ...
Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and affects this current, triggering the alarm. Compared to the alternative optical smoke detector, the ionization smoke detector is cheaper and can detect particles which are too small to produce significant light scattering; however, it is more prone ...
It decays by either emitting an alpha particle (with a decay energy of 5.27 MeV) [15] to become 239 Np, which then quickly decays to 239 Pu, or rarely, by spontaneous fission. [16] As for the other americium isotopes, and more generally for all alpha emitters, 243 Am is carcinogenic in case of internal contamination after being inhaled or ingested.
When the sensors start to wear out, your detector becomes less reliable and in order to keep you and your home safe, you want to have a fully functioning smoke detector at all times.
Some smoke detectors contain a small amount of the alpha emitter americium-241. [28] The alpha particles ionize air within a small gap. A small current is passed through that ionized air. Smoke particles from fire that enter the air gap reduce the current flow, sounding the alarm.
Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. [ 57 ] 253 Cf is at the end of a production chain that starts with uranium-238, and includes several isotopes of plutonium , americium , curium , and ...
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