Chicago Pile No 1, 1942.

Model (scale 1:8). This is a model of the world's first nuclear reactor, or atomic pile, built by Enrico Fermi (1901-54) on a squash court at the University of Chicago, USA, in 1941. On December 2 1942, it went critical for the first time, and the first self- sustaining nuclear reaction was achieved. This picture is a close up showing the hoist and emergency rod weight.