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
Enrico Fermi Nuclear Generating Station site. The first unit's construction started on August 4, 1956 and reached initial criticality on August 23, 1963, and the second unit received its construction permit on September 26, 1972. It reached criticality (head on) in June 21, 1985 and was declared commercial on November 18, 1988. The plant is connected to two single-circuit 345 kV Transmission Lines and 3 120 kV lines. They are operated and maintained by ITC Transmission. The plant is named after the Italian nuclear physicist Enrico Fermi, most noted for his work on the development of the first nuclear reactor as well as many other