Constructing CP-1

In November 1942, in the squash court beneath the West Stand of Stagg Field, construction began on a nuclear reactor that was designated Chicago Pile-1 (CP-1). Layers of graphite blocks containing slugs of uranium metal and uranium oxide alternated with layers of solid graphite blocks, gradually forming a roughly spherical shape supported by a wooden framework. A specially ordered cubical balloon-cloth bag encased the reactor to reduce absorption of neutrons by nitrogen in the air. Higher grades of uranium became available as work progressed, allowing the pile to be redesigned in a somewhat reduced size with a flattened top.

A black and white photo of the fourth layer of Chicago Pile-1 on the floor
CP-1 construction, layer 4, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
CP-1 construction, layer 4, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
A black and white photo of layer 17 of Chicago Pile-1, which is a more circular layer.
CP-1 construction, layer 17, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
CP-1 construction, layer 17, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
A black and white photo of part of layer 25 of Chicago Pile-. The layer is a jagged circle.
CP-1 construction, layer 25, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
CP-1 construction, layer 25, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
A black and white photo of layer 29 of Chicago Pile-1. The layer is so large the edges cannot be seen in the photograph, and loose bricks sit on top of the layer.
CP-1 construction, layer 29, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
CP-1 construction, layer 29, photograph, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
A black and white detailed drawing of the area where Chicago Pile-1 was constructed.
CP-1, Stagg Field West Stand, perspective drawing by Melvin Miller, 1946

University of Chicago Photographic Archive, The Hanna Holborn Gray Special Collections Research Center, University of Chicago
Handwritten measurements from the Chicago Pile-1 experiments
Measurements in Chain Pile, December 1, 1942

Herbert L. Anderson Papers, The Hanna Holborn Gray Special Collections Research Center, University of Chicago