actinide
noun
ac·ti·nide
ˈak-tə-ˌnīd 
: any of the series of elements with increasing atomic numbers that begins with actinium or thorium and ends with lawrencium see Periodic Table
Examples of actinide in a Sentence
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In such a cycle, used nuclear fuel is reprocessed to separate plutonium and other actinides from fission products.
—
Aman Tripathi, Interesting Engineering, 18 Sep. 2025
This type of star, known as an actinide-boost star, has a high abundance of radioactive elements known as actinides.
—Victoria Corless, Space.com, 4 June 2025
After 200 years, the decay heat of HLW would be reduced by a factor of up to 30 in all minor actinide-burning schemes as compared to the reference PWR once- through scheme.
—James Conca, Forbes, 27 Apr. 2021
To form their artificial actinides, the team wanted to make precursors.
—David Grossman, Popular Mechanics, 22 Oct. 2019
The lanthanide and actinide series — those two rows floating by themselves, named after their first members, lanthanum and actinium — are isolated like that as a concession to limited space.
—Bill Andrews, Discover Magazine, 26 June 2019
Uranium is currently the actinide of choice for the industry, used (sometimes with a little plutonium) in 100 percent of the world’s commercial reactors.
—Richard Martin, WIRED, 21 Dec. 2009
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Aman Tripathi, Interesting Engineering, 18 Sep. 2025
This type of star, known as an actinide-boost star, has a high abundance of radioactive elements known as actinides.
—Victoria Corless, Space.com, 4 June 2025
After 200 years, the decay heat of HLW would be reduced by a factor of up to 30 in all minor actinide-burning schemes as compared to the reference PWR once- through scheme.
—James Conca, Forbes, 27 Apr. 2021
To form their artificial actinides, the team wanted to make precursors.
—David Grossman, Popular Mechanics, 22 Oct. 2019
The lanthanide and actinide series — those two rows floating by themselves, named after their first members, lanthanum and actinium — are isolated like that as a concession to limited space.
—Bill Andrews, Discover Magazine, 26 June 2019
Uranium is currently the actinide of choice for the industry, used (sometimes with a little plutonium) in 100 percent of the world’s commercial reactors.
—Richard Martin, WIRED, 21 Dec. 2009
Cite this Entry
“Actinide.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/actinide. Accessed 31 Oct. 2025.
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