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Material World
Element · Am

Americium

A synthetic element that exists in almost every home, in a quantity smaller than a grain of salt.

Radiation source

Americium is made in reactors, not mined, and yet it is probably the most widely distributed synthetic element on Earth. An ionisation smoke detector contains a speck of americium-241 whose alpha emission keeps a small volume of air conducting; smoke particles interrupt that current, and the alarm sounds.

It is a good illustration of how little of a material a use can require. The americium in a detector is measured in micrograms, and the alpha particles it emits are stopped by a few centimetres of air.

Uses

Ionisation smoke detectors are the overwhelming use, and the reason the element is manufactured at all outside research. Americium is also used in industrial gauges that measure thickness or density by how much radiation passes through a moving sheet of material.

Its long half-life and steady heat output have made it a candidate for spacecraft power sources where the usual isotope is in short supply.

Environmental impact

The hazard is not the intact detector, where the source is sealed and the emission is stopped by air. It is disposal at scale, and the fact that a very long-lived alpha emitter is being distributed into general household waste.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is sourced from

is produced by

  • Neutron irradiation — process · two further captures beyond plutonium, in kilogram quantities — and the only one of these most people own, as a fraction of a gram in a smoke detector

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Questions this page answers

Where it comes from, and what it becomes

Follow Americium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Americium → is sourced from → Plutonium → is produced by (from uranium-238 absorbing a neutron and decaying twice — produced in every power reactor whether or not anybody wants it, and recovered only by reprocessing spent fuel) → Neutron irradiation → takes as input (uranium-238 is the feedstock for everything heavier: it absorbs neutrons without fissioning, which is what starts the sequence) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Americium → is produced by (two further captures beyond plutonium, in kilogram quantities — and the only one of these most people own, as a fraction of a gram in a smoke detector) → Neutron irradiation → takes as input (uranium-238 is the feedstock for everything heavier: it absorbs neutrons without fissioning, which is what starts the sequence) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Americium → is sourced from → Plutonium → is sourced from (formed from uranium-238 in a reactor and recovered from spent fuel) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Americium → is sourced from → Plutonium → is sourced from (formed from uranium-238 in a reactor and recovered from spent fuel) → Uranium → is extracted from (the principal uranium ore, and the pitchblende the Curies worked) → Uraninite
  • Americium → is produced by (two further captures beyond plutonium, in kilogram quantities — and the only one of these most people own, as a fraction of a gram in a smoke detector) → Neutron irradiation → takes as input (uranium-238 is the feedstock for everything heavier: it absorbs neutrons without fissioning, which is what starts the sequence) → Uranium → is extracted from (the principal uranium ore, and the pitchblende the Curies worked) → Uraninite
  • Americium → is sourced from → Plutonium → is sourced from (formed from uranium-238 in a reactor and recovered from spent fuel) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (a carbonate dissolves straight into acid, which is why an oxidised orebody goes to a leach pad and the sulfide beneath it goes to a smelter) → Malachite

These are the most distinct paths back. Americium can be traced through others besides.