Lecture by prof. Robert Jacobs, as part of the 75th anniversary of the first sustained nuclear chain-reaction experiment, CP-1, held as part of the Physics Colloquium of the University of Chicago on 26 October 2017. This experiment, conducted at Stagg Field at UC on 2 December 1942, midwifed both nuclear power plants and nuclear weapons. This lecture explores how the culture of competence among nuclear scientists and health physicists created a sense of mastery over nuclear technology. This culture facilitated the dismissal of health impacts from internalized radiation (fallout), and also the belief that humans can competently manage the storage of spent nuclear fuel for millennia.