75th Anniversary: Discovery of Plutonium

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  • Author: ChemViews
  • Published Date: 14 December 2015
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
thumbnail image: 75th Anniversary: Discovery of Plutonium

Plutonium, the 94th element, was first produced and isolated at the Berkeley Radiation Laboratory, CA, USA, on December 14, 1940. The team of Glenn T. Seaborg (pictured) used the lab's cyclotron to bombard uranium with deuterons, which generated neptunium, element 93. Subsequent β-decay resulted in the formation of plutonium.


Due to the element's potential for use in atomic weapons, publication was delayed until 1946, after the end of World War II. Secretly, industrial scale production methods were developed during the war at the University of Chicago's Metallurgical Laboratory, IL, USA, headed by Seaborg. The methods were later used at manufacturing plants in Clinton, TN, and Hanford, WA, USA, in the effort to build the first nuclear weapon in the United States. A bomb with a plutonium core (nicknamed "Fat Man") was used in the bombing of Nagasaki, Japan, on August 9, 1945, the second and so far last use of an atomic bomb in warfare.


The health effects of plutonium were tested in the US in 1945 and 1946 to ensure worker safety at the production plants. Early tests on a number of different animals species showed inconclusive results for human exposure limits. The researchers then turned to human experiments to determine uptake and metabolism of plutonium, carried out at several US sites, including Rochester, NY, and Berkeley, CA. The subjects were mostly terminally ill patients that were already hospitalized before the test. The experiments were classified and in all probabilty carried out without informed consent of the test subjects.


Apart from his involvement in the discovery of plutonium, Glenn Seaborg himself was a very interesting character with an impressive scientific biography:


Glenn T. Seaborg was born on April 19, 1912, in Ishpeming, MI, USA, to a family of Swedish descent. After his undergraduate studies at the University of California, Los Angeles (UCLA), where he majored in chemistry, Seaborg moved to the University of California at Berkeley for his graduate work. There, he worked with Gilbert N. Lewis, who asked him to stay at Berkeley after he completed his Ph.D. in 1937. Seaborg used the newly-built cyclotron and discovered several new isotopes, including 131I, the iodine isotope used in treating thyroid diseases.


Seaborg, who became Assistant Professor at Berkeley in 1941, lead the team which discovered and identified plutonium in late 1940 and early 1941, as described above. In 1942, he moved to the University of Chicago's Metallurgical Laboratory to lead efforts to develop the production of plutonium on an industrial scale as part of the Manhattan Project. During Seaborg's time in Chicago, he developed the "actinide concept", which essentially postulated the existence of the 5f row of elements below the lanthanides in the periodic table. The concept was verified by the preferred oxidation states of elements 95 and 96, americium and curium, identified by his team in 1944. Seaborg patented both of them (the only chemical elements ever to be patented), which turned out to be a commercial success since small amounts of americium are used in household smoke detectors.


After the end of World War II, Seaborg returned to Berkeley as Full Professor of Chemistry. His team synthesized the next six transuranium elements between 1949 and 1958. In 1951, Glenn Seaborg received the Nobel Prize in Chemistry together with Edwin Mattison McMillan "for their discoveries in the chemistry of the transuranium elements". Apart from the Nobel Prize, he received dozens of honorary doctorates and numerous other awards. Element 106 was named seaborgium in his honor, even though naming an element after a living scientist was considered unusual and caused some controversy.


From 1961 to 1971, Professor Seaborg chaired the US Atomic Energy Commision (AEC) in Washington, D.C. During his tenure, which spanned three US presidencies, he had significant roles in both nuclear test ban treaties and non-proliferation treaties. He strongly supported the peaceful use of atomic energy for electricity production. Professor Seaborg returned to Berkeley in 1971, where he continued to teach until 1979 and served as Associate Director of the Lawrence Berkeley National Laboratory until his death. He died on February 25, 1999.


Glenn T. Seaborg is the answer to Guess the Chemist (48).


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