"Atomic" & this word describing the central region of an atom are both found before "power" & "fission"
..... 235U, 
and these found application in the burgeoning realm of nuclear powerboth the
... [DOC] [TLE] nuclear energy facts, information, pictures | Encyclopedia.com ... [PAR] The world's first exposure to nuclear power came when two fission (atomic) ... of 
somethingin this case, a liquid) mounted on a wheel around a central shaft.