Which is actually not true at all. Modern nuclear plants can be operated in load-following mode and reduce and increase their output by 10% and more within minutes.
If the economics are impossible, how is it that France currently runs 70% of its grid on nuclear and has electricity costs substantially lower than the EU average?
We don't know how much those reactors cost to build then (it was mixed with the military nuclear program and the paperwork I understand does not exist to disentangle the spending). They are cheap now because they are not being charged for the cost of their construction. We do know that France cannot afford to replace them now; new reactors would be far out of the running economically.
So economically viable if the government subsidizes the construction. I would be happy for my tax money to go to a project that gets 70% of electricity generation off of carbon.
Subsidy doesn't change what the technology costs, it just changes how that cost is paid.
Subsidy can make sense, but not because shuffling euros around under walnut shells makes the cost disappear. The argument for subsidies is generally that it helps technologies move down experience curves. This improvement is a positive externality that a pure market would not necessarily reward. Unfortunately, nuclear (and nuclear in France) has been showing NEGATIVE experience effects.
That is not true the Cour des Comptes has extensive documentation for its cost, also nuclear LTO should be preferred, but replacement is economically possible.
The main issue is that the largest cost of a nuclear power plant is the capital investment to build it and staff to run it, which is fixed. In comparison fuel costs seem to hover at about 25%.
Therefore you need to run your plant at about full power all day to have a chance to recoup the investment. With renewable, although intermittent, sources vastly undercutting nuclear energy on price many hours of the day this becomes an almost impossible calculation.
Based on this nuclear is an uniquely bad pairing together with renewables, and it will only get worse. Say you can make massive profits on average one hour per day, but that means all other methods of energy generation or storage can make the same, and still undercut you.
This isn't even factoring in that it is impossible to get insurance for a nuclear power plant.