First Nuclear Reactor — 83 Years Ago

Under the Bleachers

On December 2, 1942, a team of scientists led by Enrico Fermi achieved the world's first self-sustaining nuclear chain reaction in a converted squash court under the stands of Stagg Field at the University of Chicago. The device — called Chicago Pile-1 — was made from graphite bricks, uranium, and wooden timber. There were no radiation shields. The experiment was conducted in the middle of a city of millions, kept secret from most of the university.

How It Worked

A nuclear chain reaction occurs when a neutron splits a uranium atom, releasing energy and more neutrons, which split more atoms, releasing more neutrons — and so on. The team used cadmium rods to absorb neutrons and control the rate of the reaction. When Fermi slowly withdrew the control rods on that December afternoon, the reaction sustained itself for 28 minutes. Arthur Compton phoned James Conant in Washington: "The Italian navigator has just landed in the new world."

What Came Next

Chicago Pile-1 was part of the Manhattan Project. The same physics that powered it led to the atomic bomb less than three years later. It also led to nuclear power stations that today supply about 10% of the world's electricity. Every nuclear reactor operating anywhere on Earth is a direct descendant of Fermi's pile under those bleachers.