Chicago Pile-2

Chicago Pile-2. CP-2 was the world's second nuclear reactor, a direct successor to the pioneering Chicago Pile-1. Constructed at the Argonne National Laboratory site in Lemont, Illinois, it served as a crucial research tool for the Manhattan Project and the early Atomic Energy Commission. Its operation provided foundational data on neutron physics, radioisotope production, and reactor design that informed the development of later reactors at Hanford and Oak Ridge.

History and construction

Following the success of the first controlled nuclear chain reaction in Chicago Pile-1 under Stagg Field, the Metallurgical Laboratory team, led by Enrico Fermi, required a more permanent and capable research facility. Construction of CP-2 began in 1943 at the newly established Argonne site, a location chosen for its greater isolation from Chicago. The reactor's core components, including its graphite moderator and uranium fuel, were transported from the original Chicago Pile-1 site. Key figures in its design and relocation included physicists Walter Zinn and Herbert L. Anderson, who worked under the overall direction of Arthur H. Compton. The move and reconstruction were part of the broader wartime efforts of the Manhattan Project to advance reactor engineering beyond the initial proof-of-concept.

Design and operation

CP-2 was a significant evolution from its predecessor. It was a graphite-moderated reactor, air-cooled, and designed for greater experimental flexibility. The reactor core, roughly spherical, was constructed from layers of graphite blocks forming a lattice, with fuel consisting of natural uranium metal and uranium oxide. Unlike Chicago Pile-1, it was housed in a dedicated concrete building with a steel superstructure, allowing for enhanced safety and instrumentation. It achieved criticality in March 1945 at a very low power, initially around 10 kilowatts thermal, though it was later modified to operate at up to 100 kW. A key design feature was the inclusion of numerous horizontal experimental ports, which allowed scientists to insert materials into the neutron flux for irradiation and to extract samples of newly created radioisotopes.

Scientific significance

The reactor served as a vital neutron source for a wide array of postwar research. It was instrumental in early studies of neutron cross sections for various materials, data essential for designing the production reactors at the Hanford Site. CP-2 was also a primary production facility for the first batches of radioisotopes for peacetime use, supplying materials for medical, biological, and industrial research conducted by institutions like the Argonne Cancer Research Hospital. Experiments conducted here provided critical insights into reactor poisoning effects and the behavior of fission products. The work at CP-2 directly informed the design of the next-generation Experimental Breeder Reactor I (EBR-I) and other reactors developed during the early years of the Atomic Energy Commission.

Decommissioning and legacy

CP-2 was shut down in 1954, having been superseded by more advanced reactors at Argonne National Laboratory, such as Chicago Pile-5 (CP-5). The fuel was removed, and the reactor structure was dismantled. The core graphite blocks, which had become radioactive waste through neutron activation, were buried at a designated disposal site. The legacy of CP-2 is profound; it established the model for the modern national laboratory research reactor. Its operational history bridged the gap between the wartime urgency of the Manhattan Project and the systematic civilian nuclear research program of the Cold War. The knowledge gained from its experiments underpinned advancements in nuclear power and nuclear medicine, cementing Argonne National Laboratory's role as a leading center for nuclear science.

Category:Nuclear research reactors Category:Manhattan Project Category:Argonne National Laboratory Category:Nuclear history of the United States Category:Buildings and structures in Cook County, Illinois