December 1942
Enrico Fermi demonstrated the first nuclear chain reaction in a lab under the
squash court at the University of Chicago. In a nuclear chain reaction, a
neutron splits one uranium atom into two smaller atoms, which in turn release
energy and neutrons; these neutrons split other uranium atoms, releasing more
energy and neutrons. Eventually enough atoms are split and neutrons released
that the reaction sustains itself. The chain reaction produces energy that can
be converted to electricity or used in atomic weapons.
Fermi and his associates built a crude nuclear reactor, which they called
Chicago Pile 1, with 57 alternating layers of uranium and graphite blocks
propped up on wooden 4' x 6's. Fermi and his team finished the construction of
Chicago Pile 1 on the morning of December 2, 1942. After hours of methodical
testing, at 3:36 pm, Fermi announced, "The reaction is self-sustaining."
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