University of Chicago, Illinois ( 41°47'32.93"N, 87°36'3.74"W) was the site of the first nuclear fission chain reaction on December 2, 1942. The experiment that led to the reaction, conducted by Italian-born physicist Enrico Fermi and his colleagues, took place under the University’s football stands. That year also marks the inception of the Manhattan Project – the United States’ effort to create an atomic bomb – and Fermi’s discoveries would eventually usher in a new era of energy production and warfare.
Atomic Fission and Energy Production
Atomic fission, or the splitting of atoms, was first discovered by Otto Hahn and Fritz Strassmann in 1939. Fission involves the splitting of an atom, e.g., uranium, with a neutron. Energy in the form of heat and radiation is then released from the split atom. Fermi soon recognized the importance of this discovery – namely the potential for atomic fission to create huge amounts of energy – and began exploring the process.
Fermi first discovered that a sustained chain reaction was possible. When an atom’s nucleus is split by a neutron, this results in the release of not only energy but more neutrons. These new neutrons then work to split other nuclei and the process continues in a chain reaction. Unabated, this reaction will take such speed that it creates an atomic explosion. Fermi’s task was to create a controlled chain reaction, that is, one that would result in a flow of constant energy production and not a massive explosion.
Fermi finally settled on a design and process. His design, an atomic pile, allowed for a sustained yet controllable uranium fission reaction. He theorized that cadmium rods, inserted into the pile when fission was taking place, would absorb the neutrons and thus slowdown the process. Enough cadmium rods should stop the process completely. The process could also work in the opposite direction – that is, removing the cadmium rods would accelerate the reaction.
The First Sustained Atomic Fission Reaction
On December 2, 1942, Fermi’s theories were put to the test. The atomic pile was set up under the stands at the University of Chicago. Fermi and his team removed several of the cadmium rods and discovered that the reaction had begun. They removed and added rods from the pile and found that they could accelerate or slowdown the process just as planned. The experiment had been a success – sustained atomic fission was now a reality.
The work of Fermi and his colleagues at the University of Chicago brought about a powerful new age; it was now possible to harness atomic power for the production of energy. Yet the discovery of sustained fission would prove to have much more far-ranging and devastating effects. After Fermi’s success, the ultimate goal of the Manhattan Project – the creation of an atomic bomb – would soon be realized. On July 16, 1945, the first atomic bomb was detonated at the Trinity Site in New Mexico.
- ChemCases.com. Nuclear Chemistry: First Chain Reaction.
- Nobel Foundation. Enrico Fermi - Biography.
- PBS Online. A Science Odyssey: Fermi Creates Controlled Nuclear Reaction.