The head of the Australian energy market operator AEMO, Daniel Westerman, has rejected nuclear power as a way to replace Australia’s ageing coal-fired power stations, arguing that it is too slow and too expensive. In addition, baseload power sources are not competitive in a grid dominated by wind and solar energy anyway.
Until a weather event blocks out most of the sunlight. An extreme scenario would be what happened to the dinosaurs, however smaller scale versions or that, such as large volcano eruptions, seem entirely possible and could heavily restrict the amount of sunlight you have access to for long periods of time.
Portugal lies in Southern Europe, we get plenty of sun, and we make heavy use of solar, but that still isn’t enough sometimes, and I’m pretty sure we sometimes get our energy from Spain, who themselves use nuclear.