Nuclear reactor

The invention: 

The first nuclear reactor to produce substantial
quantities of plutonium, making it practical to produce usable
amounts of energy from a chain reaction.

The people behind the invention:

Enrico Fermi (1901-1954), an American physicist
Martin D. Whitaker (1902-1960), the first director of Oak Ridge
National Laboratory
Eugene Paul Wigner (1902-1995), the director of research and
development at Oak Ridge

Nuclear power plant

The invention: 

The first full-scale commercial nuclear power plant, which gave birth to the nuclear power industry.  



The people behind the invention:

Enrico Fermi (1901-1954), an Italian American physicist who
won the 1938 Nobel Prize in Physics
Otto Hahn (1879-1968), a German physical chemist who won the
1944 Nobel Prize in Chemistry
Lise Meitner (1878-1968), an Austrian Swedish physicist
Hyman G. Rickover (1898-1986), a Polish American naval officer