Chicago Pile-1 final uranium slugs. Chicago Pile-1 Chicago Pile-1 (CP-1) was the world's first nuclear reactor. On 2 December 1942, the first human-made self-sustaining nuclear chain reaction was initiated in CP-1, during an experiment led by Enrico Fermi. The reactor's development was part of the Manhattan Project, the Allied effort to create atomic bombs during World War II. It was built by the Metallurgical Laboratory at the University of Chicago, under the west viewing stands of the original Stagg Field. Fermi described the apparatus as "a crude pile of black bricks and wooden timbers". The reactor was assembled in November 1942, by
Aqueous homogeneous reactor hoped to design liquid-fuel reactors that would dispense with the costly destruction and processing of solid fuel elements. The formation of gas bubbles in liquid fuels and the corrosive attack on materials (in uranyl sulfate base solutions), however, presented daunting design and materials challenges. Enrico Fermi advocated construction at Los Alamos of what was to become the world’s third reactor, the first homogeneous liquid-fuel reactor, and the first reactor to be fueled by uranium enriched in uranium-235. Eventually three versions were built, all based on the same concept. For security purposes these reactors were given the code name "water boilers".