Plutonium is a by-product of the fission process in nuclear reactors, due to neutron capture by uranium-238 in particular. When operating, a typical nuclear reactor contains within its uranium fuel load about 325 kilograms of plutonium, with plutonium-239 being the most common isotope. In a power reactor, much of the energy from the fission process is due to the plutonium, complementing that from the uranium-235.

The main isotopes of plutonium are:

  • Pu-238, (half-life 88 years)
  • Pu-239, fissile (half-life 24 000 yrs)
  • Pu-240, fertile (half-life 6 500 yrs)
  • Pu-241, fissile (half-life 14 years)
  • Pu-242, (half-life 37 600 yrs)
Plutonium
Symbol: Pu
Atomic Number: 94
Atomic Weight: 244 (most stable)
Boiling Point: 3505 K
Melting Point: 913 K
Density at 300K: 19.84 g/cm3
Covalent radius: 1.08
Atomic radius: ???
Atomic volume: 12.32 cm3/mol
First ionization potental: 6.06 V
Specific heat capacity: 0.13 Jg-1K-1
Thermal conductivity: 6.74 Wm-1K-1
Electrical conductivity: 0.7*106Ω-1m-1
Heat of fusion: ??? kJ/mol
Heat of vaporization: ??? kJ/mol
Electronegativity: 1.28 (Pauling's)

Previous Neptunium---Americium Next
To the Periodic Table
(So named (Pluto) in 1942 by Glenn T. Seaborg, Arthur C. Wahl, and Joseph W. Kennedy, U.S. physicists who isolated it in 1940, because it comes next to neptunium, as Pluto comes next to Neptune) A radioactive, metallic chemical element, one of the actinides, found in trace quantities in native uranium ores and produced by bombarding uranium with deuterons.

Symbol: Pu
Atomic number: 94
Atomic weight: 244 (isotope with the longest known half-life)
Density (at room temperature and pressure): 19.84 g/cc
Melting point: 640°C
Boiling point: 3,232°C
Main valence: +4
Ground state electron configuration: [Rn]5f67s2

See also: plutonium-239

Plutonium is a heavy metal, and looks somewhat like iron. A statistically insignificant amount exists naturally in uranium ores, but the vast majority of plutonium is made by humans bombarding uranium with neutrons. Plutonium is present in spent rods of nuclear fuel. Although seen as a waste product, plutonium is itself fissionable, and could be used as an intermediate in a breeder reactor. This would allow large-scale recycling of nuclear fuel and, perhaps even more importantly, use of U-238 to create fissionable material. Reactors currently use the much less common uranium isotope U-235. Breeder reactors would allow the Earth to provide us with thousands of years of nuclear fuel. Unfortunately, the Carter Administration decided to halt all US breeder reactor development, because President Carter feared the reactor would have an adverse effect on nuclear proliferation. Of course, countries with much less secure nuclear programs have gone ahead with attempts to create breeder reactors anyway. So much for that policy.

If you were to hold plutonium in your hand, you would notice that it is warm due to radioactive decay. Unless you were planning on keeping it there for a very long time, holding plutonium would be perfectly safe. The majority of radiation is in the form of alpha particles, easily stopped by things such as paper or the skin of your hand. There is a very low level of gamma radiation as well, which is why it's a good idea to limit your direct exposure to less than 24 continuous hours or so. However, no known human being has ever suffered adverse health effects due to exposure to plutonium. Animals surrounded by very high concentrations have been more susceptible to some forms of cancer and lung disease. Naturally occurring radium poses a bigger radioactive threat.

It's also toxic, but not much moreso than lead or arsenic. You can actually ingest plutonium safely up to a certain tolerance. You've almost certainly eaten a few plutonium atoms here and there. Even past the tolerance, you're most likely looking at long-term threats to your health, rather than keeling over on the spot. It probably doesn't taste that great by itself, either.

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