B Reactor can take a tour of the reactor by advance reservation. The reactor was designed and built by E. I. du Pont de Nemours and Company based on experimental designs tested by Enrico Fermi at the University of Chicago, and tests from the X-10 Graphite Reactor at Oak Ridge National Laboratory. It was designed to operate at 250 megawatts (thermal). The reactor occupies a footprint of (about and is tall, occupying a volume of . The reactor core itself consisted of a graphite box measuring occupying a volume of and weighing . It was penetrated horizontally through its entire length by
Experimental Breeder Reactor I Arco, Idaho in 1955, the first time a city had been powered solely by nuclear power. Besides generating the world's first electricity from atomic energy, EBR-I was also the world's first breeder reactor and the first to use plutonium fuel to generate electricity (see also the Clementine nuclear reactor). EBR-1's initial purpose was to prove Enrico Fermi's fuel breeding principle, a principle that showed a nuclear reactor producing more fuel atoms than consumed. Along with generating electricity, EBR-1 would also prove this principle. EBR-I was deactivated by Argonne in 1964 and replaced with a new reactor, Experimental Breeder Reactor II.