am·​er·​i·​ci·​um | \ ˌa-mə-ˈri-shē-əm How to pronounce americium (audio) , -sē- \

Definition of americium

: a radioactive metallic element produced artificially by bombarding plutonium with high-energy neutrons — see Chemical Elements Table

Examples of americium in a Sentence

Recent Examples on the Web Many other toxic and radioactive contaminants have also been found at Rocky Flats in addition to plutonium: americium, uranium, cadmium, PCBs, beryllium, and more. Longreads, "The Grieving Landscape," 10 Aug. 2020 Readings for contaminants like uranium and americium were also found to be well below the threshold for health concerns, the report concluded. John Aguilar, The Denver Post, "New soil samples from inside Rocky Flats refuge show low plutonium levels," 6 Sep. 2019 Engineering Analytics will specifically be measuring for plutonium, americium and uranium and seeing whether levels of the radionuclides are a hazard to human health. John Aguilar, The Denver Post, "Trail plans prompt first soil samples in 13 years at Rocky Flats," 2 July 2019 The waste includes isotopes of iodine, strontium, americium, plutonium, uranium and other unstable elements, many of which are toxic as well as radioactive. Ralph Vartabedian,, "Nuclear waste will be classified as safer under a controversial Trump administration change," 5 June 2019 Inhalation of the particles, which included uranium, thorium, plutonium and americium, can increase the risk of cancer. Hal Bernton, The Seattle Times, "Study: Traces of radioactive contamination found in homes of six Hanford workers," 14 June 2018 Heavier elements are also created in a reactor core when uranium that hasn't been fissioned captures neutrons (plutonium and americium are two of these). Andrew Karam, Popular Mechanics, "Five Years Later, Cutting Through the Fukushima Myths," 11 Mar. 2016 State monitoring has found that plutonium and americium particles traveled as far as 10 miles from the demolition site, near Richland. Annette Cary, The Seattle Times, "42 Hanford workers contaminated with radiation," 24 Mar. 2018 Outside the body, small bits of americium pose almost no threat to human health. Patrick Malone And Peter Cary, idahostatesman, "Unheeded warnings, repeated mistakes put lives at risk at Idaho nuclear lab," 10 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'americium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of americium

1946, in the meaning defined above

History and Etymology for americium

New Latin, from America + New Latin -ium

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Time Traveler for americium

Time Traveler

The first known use of americium was in 1946

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Cite this Entry

“Americium.” Dictionary, Merriam-Webster, Accessed 24 Jan. 2021.

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am·​er·​i·​ci·​um | \ ˌam-ə-ˈris(h)-ē-əm How to pronounce americium (audio) \

Medical Definition of americium

: a radioactive metallic element produced by bombardment of plutonium with high-energy neutrons symbol Am — see Chemical Elements Table

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