Not sure about Europe, but nuclear seems to be expensive in the US because construction costs are high because of overcautious regulation[1]. It was considerably cheaper in the 50/60s here, and it seems like mostly a policy issue
The reason nuclear regulation in the US is stricter these days is because companies used to do things like routing all their supposedly-redundant control and monitoring wiring through the same shared duct, stuffing it full of flammable foam, and then testing that for air leaks using a bare candle whilst the plant is operating. This is not a hypothetical problem - it was apparently standard practice in the era you're talking about and nearly caused a major catastrophe, and the fire regulations that stop practices like this are cited as a major cost making it hard to build nuclear power plants by companies in the business.
That's the point. Nuclear is getting over-regulated to be safe, not to make any mistakes. I don't disagree with the regulators. I disagree with overly cheap nuclear. Overall, no power generation method can replace nuclear's steady output with its level of cleanness and safeness.
On the other hand, nuclear is far, far safer than almost every other kind of energy source. If we allowed nuclear to be as unsafe as coal, how much cheaper might it be?
Nuclear is expensive with a $200 million liability cap for accidents. By comparison, that's roughly 0.2-0.5% of what the total cost of dealing with Fukushima will cost.
If we think it's over-regulated the first regulation that should go should be that $200 million liability cap.
Then perhaps private insurers can decide for themselves what level of safety is required to protect them from a potential $1 trillion cleanup cost they'd be on the hook for.
If the nuclear industry can convince them it's worth it at all, that is.
Do cars pay for the possibility of crude oils spilled in the ocean? Was the Deepwater Horizon insured for the full amount of dealing with the disaster? Does coal energy plants pay for future diseases of people breathing air from their chimney? Does wind turbines pay for people that suffer from low frequency sounds and solar flickers?
All energy sources have uncertainties. We've been using much much more dangerous energy sources than nuclear. So the question is yours; why do you assume the worst only for nuclear when nuclear is the only source that is preparing for the worst?