Chicago Pile 3



Chicago Pile 3 (CP-3) was the first heavy water reactor to go critical on the 15th of may, 1944. It was in operation from 1943-1954 and was built near Lemont, Illinois on the former (i.e., original) site of Argonne National Laboratory. The site is now known as the Site A/Plot M Disposal Site and is situated within Red Gate Woods, part of the Cook County Forest Preserve system.

CP-3 was initially fueled with natural uranium and used heavy water as a neutron moderator. In January 1950, the reactor was dismantled due to suspicion of corrosion of the aluminum cladding that surrounded the control rods. The reactor was rebuilt and redesignated CP-3' (Cp-3 prime). It was restarted in May 1950 and operated until 1954. The reactor was authorized to operate up to 300 kilowatts.

The two versions of the reactor were used in physics studies, fission product separations, tritium recovery from irradiated lithium, and studies of radionuclide metabolism in laboratory animals. After the reactor was decommissioned, the fuel and heavy water were shipped to the Oak Ridge National Laboratory. The containment shell for the reactor had pipes, valves, and building debris placed inside and was then filled with concrete. The 800-ton shell was buried on the site in a 40 ft deep pit. Today, a historical marker commemorates the site of CP-3 and its sister reactor CP-1/CP-2.