"Atomic" & this word describing the central region of an atom are both found before "power" & "fission"
Many isotopes of uranium 
can undergo fission, but uranium-235, which is found naturally at a ratio of .... A 
mug shot taken by the regional Colombia control agency in... [DOC] [TLE] Atomic Nucleus | Article about Atomic Nucleus by The Free Dictionary [PAR] The central region of an atom.