PU
  物理部件,物理單元
  Pu
       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: plutonium,
            atomic number 94]