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Material World
Element · Pm

Promethium

The lanthanide with no stable isotope, which kept watch faces glowing after radium was abandoned.

Radiation source

Promethium is the one gap in the lanthanide series: every isotope is radioactive, none is long-lived enough to have survived in the Earth, and what exists is made in reactors or recovered from spent fuel.

It emits beta particles and almost no penetrating radiation, which is exactly what luminous paint needs. When radium's hazards became undeniable, promethium was one of the replacements — a source that excites a phosphor without irradiating the wearer through the case.

Uses

Luminous signs and dials were the main historical use, since replaced in most consumer products by tritium or by phosphors that simply store daylight.

Promethium is also used in thickness gauges, where absorption of its beta particles measures a moving sheet without touching it, and has been used in long-lived nuclear batteries for applications where replacing a cell is impossible.

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 · the same way, and the reason an element with no stable isotope is available at all

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 Promethium 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

  • Promethium → is produced by (the same way, and the reason an element with no stable isotope is available at all) → 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
  • Promethium → is sourced from → 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
  • Promethium → is sourced from → Uranium → is extracted from (the principal uranium ore, and the pitchblende the Curies worked) → Uraninite
  • Promethium → is sourced from → 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
  • Promethium → is sourced from → 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
  • Promethium → is produced by (the same way, and the reason an element with no stable isotope is available at all) → 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. Promethium can be traced through others besides.