December 2, 2013

On this Day in 1942: Initiating the World’s First Nuclear Chain Reaction

by Heather Falconer


Drawing of CP-1, the Stagg Field Reactor

On this day 71 years ago, physicists Enrico Fermi and Léo Szilárd, along with Martin Whittaker, Walter Zinn, George Weil, and Arthur Compton, gathered together in a squash court under the west stands of the University of Chicago’s abandoned Stagg Field. In the center of the court, as Fermi explained, was “a crude pile of black bricks and wooden timbers;” a stacked pile of graphite and uranium, with large removable rods of cadmium, indium, and silver.

The group had gathered to conduct a crucial experiment as part of The Manhattan Project; an experiment that would send research in energy and weaponry in a totally new direction. Without any radiation shielding or cooling system, Fermi’s team initiated the world’s first controlled nuclear chain reaction.

Nuclear fission, the process of splitting an atom, had been talked about significantly in the physics community for some time leading up to the experiment. Einstein posited the mass–energy equation E=mc2 to describe how the splitting of a heavy atom (converting mass into energy) would simultaneously release massive amounts of energy. So much energy, in fact, that it would create a deadly explosion.

The Trinity Test, an application of nuclear chain reactions in weaponry, was the first detonated nuclear bomb.

Fermi, Einstein, and others believed that it was possible to initiate a reaction in such a way as to control the speed at which the reaction took place. With the assistance of his team at the University of Chicago, Fermi devised just such a control. As described in Visionlearning’s Nuclear Chemistry module, during nuclear fission a neutron is “fired” at the nucleus of an atom. This neutron acts like a bullet, splitting the atom and sending neutrons outward toward other atoms, causing a chain reaction.

Fermi and his team knew that when this reaction took place very quickly, it would result in a massive explosion. But if they were able to slow the process down, it would be possible to produce a slow and steady release of energy that could be harvested as a fuel source. The means by which this reaction rate was slowed was with the use of “control rods.” These rods were made of cadmium and other neutron-absorbing material. When inserted into a reactor, the rods would absorb the fast-moving neutron and slow or stop the reaction.

On December 2, 1942, the Team put their theories to the test. If they were right, they would change the face of energy and weaponry research. If it went wrong, they would blow up a significant part of Chicago. Fortunately for Chicago, the theories were correct.

Directly after the experiment took place, Arthur Compton, the head of the Metallurgical Laboratory at the University of Chicago, phoned the National Defense Research Committee with a coded message. Speaking to James Conant, Compton stated: “The Italian navigator has landed in the New World.”

Conant’s reply: “How were the natives?”

Compton: “Very friendly.”



You can learn about nuclear reactions and use interactive animations in Visionlearning’s Nuclear Chemistry module.

Discover more about Fermi and his work at PBS: A Science Odyssey

Heather Falconer

Written by

Heather Falconer holds undergraduate degrees in Graphic Arts and Environmental Science, as well as an MFA in Writing and an MLitt in Literature. She is currently completing her PhD in Rhetoric and Composition, with an emphasis on rhetoric in/and/of science. Heather has worked internationally in academic publishing as both an author and editor, and has taught a wide range of topics – from research writing to marine biology – in the public and private educational sectors.

The views expressed above do not necessarily represent those of Visionlearning or our funding agencies.