Site A
The Site A/Plot M Disposal Site is located within Red Gate Woods and situated on the former grounds of Argonne National Laboratory and its predecessor, the University of Chicago Metallurgical Laboratory in Cook County, Illinois and is now part of the Palos Forest Preserve. The site contains buried radioactive waste from contaminated building debris, and the Chicago Pile-1 (CP-1/CP-2), and Chicago Pile-3 (CP-3) nuclear reactors.
Shortly after the December 1942 demonstration of the first self-sustaining chain reaction at the University of Chicago, the research group led by Enrico Fermi needed to move to a larger, more remote laboratory campus. The U.S. Army Corps of Engineers leased 1,025 acres (4.15 km2) from the Forest Preserve District of Cook County, and placed the wartime reactor laboratory on 19 acres (77,000 m2) within the forest. The first reactor, CP-1, was disassembled and moved to Site A in March 1943, renamed as Chicago Pile 2. In May 1944 the laboratory first operated a second, heavy water-moderated reactor, CP-3 on the site. Argonne National Laboratory obtained an even larger, permanent site in Du Page County in 1947 and began moving its operations out of Site A to the new site. The two reactors operated until 1954, conducting reactor research and production of tritium. Decontamination and demolition of the buildings began in 1955. The reactors were defueled and the concrete shell for CP-3 was imploded and buried. In 1956 the property was returned to the forest preserve. Two granite monuments mark Site A and Plot M.
The Site A marker reads:
THE WORLD'S FIRST NUCLEAR REACTOR WAS REBUILT AT THIS SITE IN 1943 AFTER INITIAL OPERATION AT THE UNIVERSITY OF CHICAGO THIS REACTOR (CP-2) AND THE FIRST HEAVY WATER MODERATED REACTOR (CP-3) WERE MAJOR FACILITIES AROUND WHICH DEVELOPED THE ARGONNE NATIONAL LABORATORY THIS SITE WAS RELEASED BY THE LABORATORY IN 1956 AND THE U.S. ATOMIC ENERGY COMMISSION THEN BURIED THE REACTORS HERE.
...
Wikipedia