What is "Symmetric Fission"? Dose anyone has a clue what Symmetric Fission is?
I couldn't find any explanation on what is it on internet.
 A: It seems to me that "symmetric fission" refers to any fission process where the end products are symmetric about some point. Specifically, where the end products are symmetric in their atomic mass. 
This website explains it quite well, but for completeness I'm quoting the relevant paragraph in the article below.

It is thought to be helpful for a better understanding to take the
  atomic numbers into consideration. The atomic numbers of the
  above-mentioned elements are: Ru = 44, Rh = 45, Pd = 46, Ag = 47, Cd =
  48, In = 49 and Sn = 50, respectively. By noticing that the atomic
  number 46 of palladium is just half that of 92 of uranium, it is
  supposed that one uranium atom splits into two palladium isotopes.
  When rhodium (atomic number 45) is produced with some probability
  (cross section), silver (atomic number 47) is the counter fragment. In
  the same way, ruthenium (atomic number 44) and cadmium (atomic number
  48) are the pairing fragments. Thus, the nuclear fission observed by
  Nishina and Kimura is highly symmetric.

