The Discovery and First Isolation of Plutonium

(and other heavy metal excursions)

By John Langridge

Department of Chemistry, The University of North Texas

jlangridge@sbcglobal.net

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Significance of Pu Discovery1,2

First time a synthetic element had ever been isolated in weighable quantitiesFirst time weighable quantities of “transmutation products” created in particle acceleratorEnd of WW2 in Pacific theaterDevelopment of beautiful, ultra - micro scale Chemistry

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Importance of Understanding Plutonium Chemistry Today5

Waste management issues and environmental impact

Weapons programs

Nuclear EnergyLarge scale electricity generation

Space travel (238)

Pacemakers (238)

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How was Plutonium Created?

5 kg uranyl nitrate hexahydrate (U238) + 12 Mev Neutrons from the Berkeley 60-inch cyclotron in (d,n) reaction with Be1

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The Post-Irradiation Product

Mixture of Pu, Np, U, and other fission products1

Separated and concentrated using lanthanides in sulfuric acid solution followed by series of “fluoride cycles”1

Concentration occurred in Berkeley while isolation occurred in Chicago1

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Concentration and Isolation1

Part1: Fluorides Sulfates

Evaporation to half original volume2 mL 27M HF 5M KF added to precipitate the lanthanide and Plutonium FluoridesResulting precipitate contributed 70K cpm vs. 300 cpm remaining in solutionSulfuric acid + heat + precipitate soluble lanthanide and Plutonium sulfates

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Concentration and Isolation1

Part2: Sulfates oxidized Pu soluble Fluoride

2 mL 2M nitric acid to dissolve the sulfateSilver Oxide oxidizes Plutonium to Fluoride soluble state2M HF precipitates the lanthanides as insoluble Fluorides leaving Pu in solution as soluble Fluoride (95% efficient)Wax coated syringes and glassware utilized

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Concentration and Isolation1

Part 3 soluble fluorideinsoluble fluoride

Fluoride solution evaporated in sulfuric acid

Reduction to insoluble Fluoride

Fluoride cycle begins again using higher purity reagents

Results in higher purity product

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The First Isolated Sample2

Approximately 1 µg Fluoride

Magnified 30 X

Solubility 5mg/L through specific activity analysis (assumed 30k year t1/2)

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What was learned?2

Lower oxidation state carried by fluorides of lanthanide (La and Ce)Lower state Higher state using silver ions

Higher state Lower state using SO2 or Br-

Pu(aq) + (Zn) Pu(s) Reduction doesn’t occurMultiple redox cycles can remove all but contaminants most like Pu (Sm, for example)Specific activity can accurately estimate mass and solubilityNew methods for ultra micro-chemical analysis

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Discoveries that followed3

95 Americium (1944)

96 Curium (1944)

97 Berkelium (1949)

98 Californium (1950)

99 Einsteinium (1952)

100 Fermium (1952)

101 Mendelevium (1955)

102 Nobelium (1956)

103 Lawrencium (1961)

104 Rutherfordium (1966)

105 Dubnium (1968)

106 Seaborgium (1974)

107 Bohrium (1981)

108 Hassium (1984)

109 Meitnerium (1982)

110 Darmstadtium (1994)

111 Roentgenium (1994)

112 Copernicium (1996)

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State of the Art: Gas flow transport and detection and

“online” Chemistry4

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References1) Cunningham, B.B. and Werner, L.B. “The First Isolation of

Plutonium.” Journal of the American Chemical Society 71.5 (1949): 1521-1524. Print

2) Seaborg, Glenn T. “Forty Years of Plutonium Chemistry: The Beginnings.” Washington: ACS Symposium Series American Chemical Society, 1983. 1-22. Print.

3) “Transuranium Elements." Encyclopedia Britannica Online. Encyclopedia Britannica, 2010. Thursday, November 18, 2010.

4) Eichler, R. et al. “Chemical characterization of element 112." Nature 447.3 (2007): 72-75. Print.

5) Clark, David. “The Chemical Complexities of Plutonium.” Los Alamos Science 20.1 (2000):365-381. Online

Development of Ultra-micro-scale hardware1

Development of Ultra-micro-scale hardware1