plu·to·ni·um /pluˈtoniəm/
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 plu·to·ni·um /pluˈtonɪəm/ 名詞
 鈽


 plutonium
      n : a solid silvery gray radioactive transuranic element  whose
          atoms can be split when bombarded with neutrons; found in
          minute quantities in uranium ores but is usually
          synthesized in nuclear reactors; 13 isotopes are known
          with the most important being plutonium 239 [syn: Pu, {atomic
          number 94]


 plutonium
 Symbol: Pu
 Atomic number: 94
 Atomic weight: (242)
 Dense silvery radioactive metallic transuranic element, belongs to the
 actinoids. Pu-244 is the most stable isotope with a half-life of 7.6*10^7
 years. Thirteen isotopes are known. Pu-239 is the most important, it
 undergoes nuclear fission with slow neutrons and is hence important to
 nuclear weapons and reactors. Plutonium production is monitored down to
 the gram to prevent military misuse. First produced by Gleen T. Seaborg,
 Edwin M. McMillan, J.W. Kennedy and A.C. Wahl in 1940.