Leo Szilard

Leo Szilard was a Hungarian-American physicist who conceived the idea of the nuclear chain reaction in 1933 and filed a secret patent on it, recognizing before almost anyone else that a controlled chain reaction in a suitable material could release usable energy at an enormous scale. He worked with Enrico Fermi at Columbia University and later the University of Chicago to help build Chicago Pile-1, the first artificial nuclear reactor, which first went critical in December 1942. Szilard also drafted the 1939 letter that Albert Einstein signed and sent to President Franklin Roosevelt warning of the possibility of an atomic bomb, setting the Manhattan Project in motion, though he later campaigned against the weapons use and for civilian control of nuclear energy. His patent for the nuclear reactor, filed jointly with Fermi, is one of the foundational documents of the entire nuclear power industry.