Each of those existing plants were competitive against coal at the time without having the negative externalities of widespread radiation exposure (uranium in coal just released to the atmosphere); mercury contamination in all our freshwater lakes and the ocean, leading to strict limits on consuming fish for children and pregnant women; and a half-century of CO2 emissions.

Orders of magnitude more people are killed by rooftop solar, but we haven't raised safety standards on all other sources of electricity to be the same level we require for nuclear.