Chain Reaction

Construction on CP-1 halted at the fifty-seventh layer on December 1, 1942, when measurements indicated the pile would become self-sustaining once the control rods were withdrawn. On Wednesday, December 2, Fermi and his colleagues gathered on the balcony of the West Stand squash court to complete their test of the reactor. After tests in the morning and a break for lunch, the last control rod was slowly withdrawn until the "critical," or self-sustaining, level was reached. The scientists then watched the reactor operate for twenty-eight minutes before reinserting the rod and stopping the reaction. CP-1, the world’s first nuclear reactor, was an operational success. Arthur H. Compton telephoned Harvard University president James B. Conant, a member of the Manhattan Project Military Policy Committee, to convey the news: "The Italian navigator has just landed in the New World."

A black and white photo of a scale model of CP-1 from the corner of the model, including miniature scientists — CP-1 scale model, photograph, undated

University of Chicago News Office Records, The Hannah Holborn Gray Special Collections Research Center, University of Chicago

A black and white photo of a scale model of CP-1 from the front, including miniature scientists — CP-1 scale model, photograph, undated

University of Chicago News Office Records, The Hannah Holborn Gray Special Collections Research Center, University of Chicago

A black and white photo of a scale model of CP-1 as it would appear inside the buildling that housed it

CP-1 scale model, photograph, undated

University of Chicago News Office Records, The Hannah Holborn Gray Special Collections Research Center, University of Chicago

CP-1 galvanometer graph, December 2, 1942

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

A black and white close-up photo of a bottle of Chianti champagne with a wooden sheath around the bottom of the bottle, held in a man's hands

Chianti bottle with CP-1 scientists’ signatures in hands of Albert M. Wattenberg, photograph, 1952

University of Chicago News Office Records, The Hannah Holborn Gray Special Collections Research Center, University of Chicago

A typed page describign work carried out by the team of scientists

Manhattan Engineer District, Metallurgical Project. “Report for Month Ending December 15, 1942.”

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

A black and white photo of a group of men and one woman who were the scientists working on CP-1, standing in front of a building on campus,

CP-1 scientists, Eckhart Hall, University of Chicago, photograph, December 2, 1942

University of Chicago Photographic Archive, The Hanna Holborn Gray Special Collection Research Center, University of Chicago

A typed page with each CP-1 scientist's name typed, followed by their signature

Scientists present at the operation of CP-1, December 2, 1942

University of Chicago News Office Records, The Hanna Holborn Gray Special Collections Research Center, University of Chicago

A typed letter from Marvin Wilkening to P.W. Bishop — Letter, Marvin Wilkening to P.W. Bishop, January 15, 1962

Marvin Wilkening Papers, The Hanna Holborn Gray Special Collections Research Center, University of Chicago