On December 20, 1951, electricity generated by Experimental Breeder Reactor I (EBR-I) powered four light bulbs. It was the first use of electrical power generated by nuclear fission.

EBR-I had its genesis in the presumption that natural supplies of uranium were limited:

During the war [World War II] and immediately afterward, the assumption that uranium was scarce continued to influence the way governments and scientists regarded it. The scarcity was felt to be so serious that General Groves [Director of the Manhattan Project], who continued to administer the Manhattan District after the war, approved a proposal in 1946 to build a reactor that would help solve the uranium shortage.

Proving the Principle, Susan M. Stacy

One way of creating more of the type of material that was needed to build nuclear weapons had been proposed by the first director of Argonne National Laboratory, Dr. Walter Zinn. Zinn, who had worked with Enrico Fermi on the CP-1, made a proposal for a type of nuclear reactor that would create plutonium, a material that can sustain a chain reaction, from natural uranium, a material that cannot. Zinn's proposal became reality in 1951, when Experimental Breeder Reactor I (EBR-1) achieved a self-sustaining chain reaction.