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CP-1 70th Anniversary

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Celebrating the 70th Anniversary of Chicago Pile 1 (CP-1)


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Reactors Designed by Argonne National Laboratory

Early Exploration

Early exploration nuclear reactors designed by the Manhattan Project's Metallurgical Laboratory, the direct predecessor to Argonne National Laboratory, began the development of nuclear technology.

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CP-1 (Chicago Pile 1 Reactor)

CP-1 reactor

This drawing depicts the historic Dec. 2, 1942, event -- the first controlled, self-sustaining nuclear chain reaction. It took place under the abandoned football stands at the University of Chicago. Click on photo to view a larger image.

Chicago Pile 1 was the world's first nuclear reactor, built in 1942 by Nobel Prize winner Enrico Fermi. The reactor was built underneath the University of Chicago's Stagg Field football stadium. On Dec. 2, 1942, Enrico Fermi and 48 of his colleagues succeed in achieving in this reactor the world’s first man-made controlled nuclear chain reaction, thereby establishing the ability of mankind to control the release of nuclear energy. He and other scientists from that group later founded Argonne National Laboratory.

CP-1 reactor model

Scale model of CP-1 reactor. Courtesy Archival Photographic Files, [apf2-00504], Special Collections Research Center, University of Chicago Library.
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The photograph at right shows a scale model depicting Fermi’s reactor setup on that day in 1942. The model shows a segment of the football stadium and gives a perspective on where the reactor was located under the stands. Fermi and his colleagues were assembled on the balcony to the right to observe the instruments recording the neutron intensity in the pile. After the reactor had sustained the chain reaction for 28 minutes the operators to the right of the reactor (in the left foreground of the photo) pushed in a cadmium control rod called zip, which absorbed neutrons and ended the chain reaction. The reactor fuel was lumps of uranium metal and uranium oxide; these were spaced on a cubic lattice within layers of graphite, with some graphite layers containing only uranium metal pseudospheres, some only uranium oxide pseudospheres, and some containing both. The pile was built by alternating graphite layers seeded with uranium metal and/or uranium oxide with layers of solid graphite blocks. The completed reactor contained 57 layers, which was about one layer beyond the critical stage needed to sustain the chain reaction.

Early in 1943, CP-1 was dismantled and moved to a less-populated site in the "Argonne Forest" section of the Cook County Forest Preserve in Palos Park. That part of the forest has since been renamed, but its appellation survives today in the name of Argonne National Laboratory.

Celebrating Chicago Pile 1 70th anniversary

For more information on CP-1:

CP-2 (Chicago Pile 2 Reactor)

Chicago Pile 2 Reactor

In early 1943, Chicago Pile 1 was dismantled at the University of Chicago, moved to the Argonne Forest section of the Palos Hills Forest Preserve, and renamed Chicago Pile 2. Click on photo to view a larger image.

In early 1943 Manhattan Engineer District disassembled Chicago Pile 1 and rebuilt it at Palos Park, IL, as Chicago Pile 2. CP-2 had a thermal- power level of 10 kW. The fuel for CP-2 was natural uranium (uranium in which the natural abundance of the isotopes uranium-234, uranium-235, and uranium-238 has not been altered). A small laboratory atop the 14,000-ton reactor provided space for limited experiments using neutrons from the reactor's core. The reactor's face contained ports through which materials could be inserted into the core for irradiation.

For more information on CP-2:

CP-3 (Chicago Pile 3 Reactor)

The Chicago Pile-3 reactor

The Chicago Pile-3 reactor. Click on photo to view a larger image.

Chicago Pile 3 was the world's first "heavy-water moderated" reactor. It was designed by Eugene Wigner; at Enrico Fermi's request, Walter Zinn directed its construction in the Argonne Forest in 1943. Chicago Pile 3 achieved criticality in 1944.

The fuel was, as in the case of the CP-2 reactor, natural uranium. CP-3 was dismantled in January 1950 because of suspected corrosion of the aluminum cladding around some of the fuel rods. The natural uranium fuel in CP-3 was replaced with enriched uranium (uranium in which the amount of uranium-235 in the fuel has been increased from its naturally occurring abundance). The redesigned reactor, named CP-3’ ("CP-3 prime"), became operational in May 1950. CP-3’ shut down in 1954. CP-3 was shared with the Canadians, who used it in the design of the Canadian NRX reactor, from which the 27 CANDU commercial power reactors evolved.

Research programs conducted at CP-3 and CP-3’ included reactor physics studies, fission product separations, tritium recovery from irradiated lithium, and studies of radionuclide metabolism in laboratory animals.

For more information on CP-3:

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Last Modified: Mon, November 10, 2014 1:51 AM

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