ARGONNE NATIONAL LABORATORY / SCIENCE PHOTO LIBRARY ARGONNE NATIONAL LABORATORY / SCIENCE PHOTO LIBRARY
Painting depicting the moment at which the first self-sustaining nuclear chain reaction occurred, at 3.36 pm on December 2, 1942. The pile was built by a team led by the Italian physicist Enrico Fermi in a squash court under the stands of Chicago University's Stagg Field, and consisted of a complex lattice of bricks of graphite & "slugs" of uranium. At bottom centre is George Weil, operating one of the control rods. At top right is the 'liquid control squad', armed with buckets of a solution of a cadmium salt (in case of mechanical failure of the control rods).
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