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Properties of Plutonium Metal

(Plutonium metal is used in nuclear weapons)

Compiled by Annie Makhijani

Physical characteristics
Color silver
Melting point 641 centigrade
Boiling point 3,232 centigrade
Density 16 to 20 g/cm3
How plutonium metal reacts in air
FORMS AND AMBIENT CONDITIONS REACTION
Non-divided metal at room temperature relatively inert, slowly oxidizes (corrodes)
Divided metal at room temperature readily reacts to form plutonium dioxide (PuO2)
Finely divided:
  • particles under 1mm diameter
  • particles over 1mm diameter


  • pyrophoric (spontaneously ignites) at about 150 degrees C1
  • pyrophoric at about 500 degrees C
    		•
    Humid, elevated temperatures readily reacts to form plutonium dioxide (PuO2)
    Solubility of plutonium metal in acids
    Hydrochloric acid (HCl) soluble
    Perchloric acid (HClO4) soluble
    Phosphoric acid (H3PO4) soluble
    Nitric acid (HNO3) insoluble2


    Important Plutonium Compounds and their Uses

    COMPOUND USE
    Oxides
    Plutonium Dioxide (PuO2)
    		 can be mixed with uranium dioxide
    (UO2) for use as reactor fuel
    Carbides
    Plutonium Carbide (PuC)
    Plutonium Dicarbide (PuC2)
    Diplutonium Tricarbide (Pu2C3)
    		 all three carbides can potentially
    be used as fuel in breeder reactors
    Fluorides
    Plutonium Triflouride (PuF3)
    Plutonium Hexaflouride (PuF4)
    		 both fluorides are intermediate compounds in
    the production of plutonium metal
    Nitrates
    Plutonium Nitrate (PuNO3)
    		 no use, but it is a product of reprocessing
    (extraction of plutonium from used nuclear fuel)


    Important Plutonium Isotopes Radiological Properties

    The plutonium isotopes listed below are "fissionable", which means that the nuclei can be split into two fragments, called fission products. In addition to being fissionable, plutonium-239 and plutonium-241 are "fissile" -- that is, they can be split by neutrons of very low (ideally zero) energy. This means that they can be assembled into a critical mass, and hence can sustain a chain reaction without an external source of neutrons.

    Pu-238 Pu-239 Pu-240 Pu-241 Pu-242
    Half-life
    (in years)    		 87.74 24,110 6,537 14.4 376,000
    Specific activity
    (curies/grams)    		 17.3 0.063 0.23 104 0.004
    Principal
    decay mode    		 alpha alpha alpha
    some spontaneous
    fission3    		 beta alpha
    Decay energy
    (MeV)    		 5.593 5.244 5.255 0.021 4.983
    Radiological
    hazards    		 alpha,
    weak gamma    		 alpha,
    weak gamma    		 alpha,
    weak gamma    		 beta,
    weak gamma4    		 alpha,
    weak gamma
    How isotope
    is produced    		 nuclear
    reactors    		 nuclear
    reactors    		 nuclear
    reactors    		 nuclear
    reactors    		 nuclear
    reactors
    Main Uses Production of thermoelectric power used in nuclear weapons, satellites, and heart pacemakers Fissile material for nuclear weapons, and for the production of energy None None None

    Source: CRC Handbook of Chemistry and Physics, 1990-1991. Varioius sources give slightly different figures for half-lives and energies. Notes:
    1 US Department of Energy, "Assessment of Plutonium Storage Safety Issues at Department of Energy Facilities," DOE/DP-0123T (Washington, DC: US DOE, January 1994).
    2 Plutonium metal is insoluble in nitric acid. Plutonium dioxide (PuO2) is slightly soluble in hot, concentrated nitric acid. But when plutonium dioxide and uranium dioxide (UO2) form a solid mixture, as in spent fuel for example, then the solubilitiy of plutonium dioxide in nitric acid is enhanced due to the fact that uranium dioxide is soluble in nitric acid.
    3 Source of neutrons causing added radiation dose to workers in nuclear facilities.
    4 Plutonium-241 decays into Americium-241, which is an intense gamma-emitter.
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    Spring 1994

    Posted January 2002