The discovery that uranium nuclei could be split, releasing large amounts of energy, was made in Berlin in 1938 by Otto Hahn and Fritz Strassmann and interpreted by Lise Meitner and Otto Frisch. The first controlled, self-sustaining nuclear chain reaction was achieved in 1942 under Enrico Fermi at the University of Chicago. This work led both to nuclear weapons during the Second World War and, from the 1950s, to civil reactors generating electricity by using fission heat to raise steam. Commercial nuclear power grew substantially in the following decades.
It reordered geopolitics through the bomb and added a major non-fossil source to electricity supply, though its direct urban footprint is limited, concentrated in a small number of large, isolated power stations rather than woven into the city fabric.
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