plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm 
: a radioactive metallic element similar chemically to uranium that is formed as the isotope 239 by decay of neptunium and found in minute quantities in pitchblende, that undergoes slow disintegration with the emission of an alpha particle to form uranium 235, and that is fissionable with slow neutrons to yield atomic energy see Chemical Elements Table
Examples of plutonium in a Sentence
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The Savannah River Site was built in 1951 as a means to produce material for nuclear weapons, primarily tritium and plutonium, to support America’s defense programs, according to the SRS website.
—
Angel Saunders, People.com, 31 July 2025
The environments around neutron star collisions are thought to be the only furnaces in the cosmos extreme enough to generate elements like gold, silver and plutonium.
—Robert Lea, Space.com, 20 July 2025
Closing the nuclear fuel cycle involves separating the uranium and plutonium that comprise more than 95 percent of nuclear waste, and recycling them back into reactors as fuel.
—IEEE Spectrum, 7 July 2025
Iran’s Arak reactor was destroyed and, with it, any near-term chance that Iran could produce weapons-grade plutonium.
—Richard Nephew, Foreign Affairs, 26 June 2025
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Angel Saunders, People.com, 31 July 2025
The environments around neutron star collisions are thought to be the only furnaces in the cosmos extreme enough to generate elements like gold, silver and plutonium.
—Robert Lea, Space.com, 20 July 2025
Closing the nuclear fuel cycle involves separating the uranium and plutonium that comprise more than 95 percent of nuclear waste, and recycling them back into reactors as fuel.
—IEEE Spectrum, 7 July 2025
Iran’s Arak reactor was destroyed and, with it, any near-term chance that Iran could produce weapons-grade plutonium.
—Richard Nephew, Foreign Affairs, 26 June 2025
See All Example Sentences for plutonium
Cite this Entry
“Plutonium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/plutonium. Accessed 7 Aug. 2025.
Copy CitationKids Definition
plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm
: a radioactive metallic element that is formed by decay of neptunium and found in minute quantities in pitchblende and that produces atomic energy by fission see element
Medical Definition
plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm
: a radioactive metallic element similar chemically to uranium that is formed as the isotope 239 by decay of neptunium and found in minute quantities in pitchblende, that undergoes slow disintegration with the emission of an alpha particle to form uranium 235, and that is fissionable with slow neutrons to yield atomic energy
—symbol Pu
see Chemical Elements Table
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