In December of 1942, in a squash court under the University of Chicago's football stadium, the Italian-American physicist Enrico Fermi pushed his team to assemble the first nuclear reactor, a room-sized pile of graphite bricks interspersed with chunks of uranium and uranium oxide. If all went well, a chain reaction of fissioning uranium atoms, triggered by neutrons, would produce a new form of energy. And perhaps a weapon. A war was on; a nuclear bomb might shorten the war and save American lives.
Graphite dust blackened walls, floors, faces, notebooks. It was dirty work, as different as one can imagine from the white-coated, dust-free environments of modern nuclear facilities.
At last the moment came to allow the reactor to go "critical." Neutron-absorbing cadmium rods were slowly removed from the pile, under Fermi's direction. There was concern that the reaction might get out of control, that the pile might melt down. A "suicide squad" of three young physicists stood by with jugs of neutron-absorbing cadmium-sulfate solution to douse the reactor.
All of this in the middle of a crowded city. It is inconceivable that such a thing would be allowed today.
The self-sustaining reaction was achieved. For four-and-a-half minutes, Fermi let neutrons multiply. Left uncontrolled, a runaway reaction would have killed everyone in the room and caused a mini-Chernobyl.
But before that happened, control rods were re-inserted and the chain reaction halted. The physicists shared a celebratory bottle of Chianti. The crowd departed. Fermi stayed behind with Leo Szilard, the physicist who had first imagined that a nuclear chain reaction was possible. Szilard shook Fermi's hand -- and worried that the day would go down as a black chapter in the history of mankind.