On 12 December 1942 CP-1's power output was increased to 200 W, enough to power a light bulb.
Lacking shielding of any kind, it was a radiation hazard for everyone in the vicinity, and further testing was continued at 0.5 W. Operation was terminated on 28 February 1943, and the pile was dismantled and moved to Site A in the Argonne Forest, now known as Red Gate Woods.
There the original materials were used to build Chicago Pile-2 (CP-2).
Instead of being spherical, the new reactor was built in a cube-like shape, about 25 feet (7.6 m) tall with a base approximately 30 feet (9.1 m) square.
It was surrounded by concrete walls 5 feet (1.5 m) thick that acted as a radiation shielding, with overhead protection from 6 inches (15 cm) of lead and 50 inches (130 cm) of wood.
More uranium was used, so it contained 52 short tons (47 t) of uranium and 472 short tons (428 t) of graphite.
No cooling system was provided as it only ran at a few kilowatts.
CP-2 became operational in March 1943, with a k of 1.055.
During the war Zinn allowed CP-2 to be run around the clock, and its design was suitable for conducting experiments.

CP-2 was joined by Chicago Pile-3, the first heavy water reactor, which went critical on 15 May 1944.

The reactors were used to undertake research related to weapons, such as investigations of the properties of tritium.
Wartime experiments included measuring the neutron absorption cross-section of elements and compounds.
Albert Wattenberg recalled that about 10 elements were studied each month, and 75 over the course of a year.
An accident involving radium and beryllium powder caused a dangerous drop in his white blood cell count that lasted for three years.
As the dangers of things such as inhaling uranium oxide became more apparent, experiments were conducted on the effects of radioactive substances on laboratory test animals.

Though held secret for a decade, Fermi patented the design, with an initial filing date of 19 Dec. 1944 as the neutronic reactor no.
2,708,656.

The Red Gate Woods later became the original site of Argonne National Laboratory, which replaced the Metallurgical Laboratory on 1 July 1946, with Zinn as its first director.
CP-2 and CP-3 operated for ten years before they outlived their usefulness, and Zinn ordered them shut down on 15 May 1954.
Their remaining usable fuel was transferred to Chicago Pile-5 at the Argonne National Laboratory's new site in DuPage County, and the CP-2 and CP-3 reactors were dismantled in 1955 and 1956.
Some of the graphite blocks from CP-1/CP-2 were reused in the reflector of the TREAT reactor.
High-level nuclear waste such as fuel and heavy water were shipped to Oak Ridge, Tennessee, for disposal.
The rest was encased in concrete and buried in a 40-foot-deep (12 m) trench in what is now known as the Site A/Plot M Disposal Site.
It is marked by a commemorative boulder.

By the 1970s there was increased public concern about the levels of radioactivity at the site, which was used by the local residents for recreational purposes.
Surveys conducted in the 1980s found strontium-90 in the soil at Plot M, trace amounts of tritium in nearby wells, and plutonium, technetium, caesium, and uranium in the area.
In 1994, the United States Department of Energy and the Argonne National Laboratory yielded to public pressure and earmarked $24.7 million and $3.4 million respectively to rehabilitate the site.
As part of the cleanup, 500 cubic yards (380 m³) of radioactive waste was removed and sent to the Hanford Site for disposal.
By 2002, the Illinois Department of Public Health had determined that the remaining materials posed no danger to public health.
On 12 December 1942 CP-1's power output was increased to 200 W, enough to power a light bulb. Lacking shielding of any kind, it was a radiation hazard for everyone in the vicinity, and further testing was continued at 0.5 W. Operation was terminated on 28 February 1943, and the pile was dismantled and moved to Site A in the Argonne Forest, now known as Red Gate Woods. There the original materials were used to build Chicago Pile-2 (CP-2). Instead of being spherical, the new reactor was built in a cube-like shape, about 25 feet (7.6 m) tall with a base approximately 30 feet (9.1 m) square. It was surrounded by concrete walls 5 feet (1.5 m) thick that acted as a radiation shielding, with overhead protection from 6 inches (15 cm) of lead and 50 inches (130 cm) of wood. More uranium was used, so it contained 52 short tons (47 t) of uranium and 472 short tons (428 t) of graphite. No cooling system was provided as it only ran at a few kilowatts. CP-2 became operational in March 1943, with a k of 1.055. During the war Zinn allowed CP-2 to be run around the clock, and its design was suitable for conducting experiments.
CP-2 was joined by Chicago Pile-3, the first heavy water reactor, which went critical on 15 May 1944.
The reactors were used to undertake research related to weapons, such as investigations of the properties of tritium. Wartime experiments included measuring the neutron absorption cross-section of elements and compounds. Albert Wattenberg recalled that about 10 elements were studied each month, and 75 over the course of a year. An accident involving radium and beryllium powder caused a dangerous drop in his white blood cell count that lasted for three years. As the dangers of things such as inhaling uranium oxide became more apparent, experiments were conducted on the effects of radioactive substances on laboratory test animals.
Though held secret for a decade, Fermi patented the design, with an initial filing date of 19 Dec. 1944 as the neutronic reactor no. 2,708,656.
The Red Gate Woods later became the original site of Argonne National Laboratory, which replaced the Metallurgical Laboratory on 1 July 1946, with Zinn as its first director. CP-2 and CP-3 operated for ten years before they outlived their usefulness, and Zinn ordered them shut down on 15 May 1954. Their remaining usable fuel was transferred to Chicago Pile-5 at the Argonne National Laboratory's new site in DuPage County, and the CP-2 and CP-3 reactors were dismantled in 1955 and 1956. Some of the graphite blocks from CP-1/CP-2 were reused in the reflector of the TREAT reactor. High-level nuclear waste such as fuel and heavy water were shipped to Oak Ridge, Tennessee, for disposal. The rest was encased in concrete and buried in a 40-foot-deep (12 m) trench in what is now known as the Site A/Plot M Disposal Site. It is marked by a commemorative boulder.
By the 1970s there was increased public concern about the levels of radioactivity at the site, which was used by the local residents for recreational purposes. Surveys conducted in the 1980s found strontium-90 in the soil at Plot M, trace amounts of tritium in nearby wells, and plutonium, technetium, caesium, and uranium in the area. In 1994, the United States Department of Energy and the Argonne National Laboratory yielded to public pressure and earmarked $24.7 million and $3.4 million respectively to rehabilitate the site. As part of the cleanup, 500 cubic yards (380 m³) of radioactive waste was removed and sent to the Hanford Site for disposal. By 2002, the Illinois Department of Public Health had determined that the remaining materials posed no danger to public health.
Chicago Pile-1