You can’t just replace coal and oil by nuclear power. it takes decades to build a new plant and is very expensive.

That’s been said for over a decade at this point. We could have had plenty of nuclear power plants and maintained/developed expertise in the area if clean energy was a goal that was taken seriously by Europe. Both solar and wind are innately inefficient in terms of W/m^2, and wind has the additional problem of noise pollution and environmental impact.