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Material World
Element · Pu

Plutonium

A synthetic element made in reactors, present in the environment only because people put it there.

Plutonium is produced when uranium-238 absorbs a neutron in a reactor, and essentially all of it in existence has been made deliberately. It is a strange metal by any standard: it has six allotropes at ordinary pressure, changes volume substantially between them, is a poor conductor for a metal, and is warm to the touch from its own radioactive decay.

Its hazard is primarily radiological rather than chemical, and specifically from inhaled particles. Its long-lived isotopes make waste management a problem measured in tens of thousands of years.

Uses

Plutonium-239 is fissile and is a weapons material and a reactor fuel. Mixed oxide fuel, blending plutonium recovered from spent fuel with uranium, is used in some civil reactors and is one route for consuming stockpiles from dismantled weapons.

Plutonium-238 has a different role entirely. It is not weapons-usable, decays with substantial heat output, and powers the radioisotope thermoelectric generators that run spacecraft too far from the Sun for solar panels — the Voyagers, Cassini, New Horizons and the Mars rovers all rely on it.

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 a source for

is sourced from

  • Uranium — element · formed from uranium-238 in a reactor and recovered from spent fuel

is used as

  • Nuclear fuel — application · as mixed oxide fuel, and as Pu-238 in spacecraft generators

is produced by

  • Neutron irradiation — process · 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

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 Plutonium 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

  • 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
  • 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
  • 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
  • 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
  • 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 (leached with acid or alkali depending on the host rock, which is what decides the flowsheet of a uranium mill) → Uraninite
  • 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 extracted from (the principal uranium ore, and the pitchblende the Curies worked) → Uraninite

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

Downstream — what it becomes