Short answers, pulled from the story.
Humanity first used nuclear energy for electricity generation on the 20th of December 1951 at the Experimental Breeder Reactor One near Arco, Idaho. This event marked the moment four light bulbs flickered to life using power from a nuclear reactor.
England opened Calder Hall as the world's first commercial nuclear power station on the 27th of August 1956. The Soviet Union connected the Obninsk Nuclear Power Plant to its grid earlier on the 27th of June 1954 but this facility served dual purposes including plutonium production.
The Chernobyl disaster occurred within the Soviet Union in 1986 involving an RBMK reactor failure. It resulted in approximately fifty-six direct deaths and cost an estimated sixty-eight billion US dollars adjusted for inflation.
Enrichment processes increase natural uranium concentration to around 3.55 percent before conversion into fuel pellets for light water reactors. Natural uranium contains only about 0.7 percent uranium-235 which is too low for these specific reactor types.
Nuclear power supplied two thousand six hundred two terawatt hours of electricity globally in 2023 representing nine percent of total generation. The United States generated almost eight hundred terawatt hours annually with an average capacity factor of ninety-two percent.