Physicists Enrico Fermi and Leo Szilard hold the first patent for a nuclear reactor. The patent was published in 1955, although the invention was based on work the two did in 1938 concerning atomic bombardment of uranium with neutrons.
The 1938 work demonstrated for the first time that nuclear chain reactions were possible under laboratory conditions. Fermi received a Nobel Prize for this discovery, but Szilard went uncredited and did not. In 1942, Szilard performed the first controlled nuclear reaction. Fermi and Szilard worked together on the Manhattan Project and refined the process of creating nuclear reactions, alongside other colleagues. Because this first reactor used neutrons to produce nuclear fission, it is called a neutronic reactor in the patent rather than the more familiar term, nuclear reactor.