> French nuclear supply chain atrophied quite lot in the last 30 years.

Because today it makes no economic sense. Supply chain for horse carts is also very atrophied.

>The South Koreans build Barakah nuclear power plant 5600 MWe for $32bn.

Still very expensive. Flamanville is an extreme when things go really bad, but 175 MWe for 1 bn is also very high. 1 bn buys ~1 GW of solar, ~1 GW of onshore wind, or ~3 GW of battery capacity. You should only build new nuclear either to get a better mix in the grid (up to 5% is the nuclear lobby recommendation), or because you have no sun and no wind.

What would you need to replace a 1 GW nuclear power plant with 98% capacity factor?

Probably 1 GW solar power plant, together with 1 GW onshore wind and 1 GW of gas power plant. Then you have to also pay the natural gas to compensate for times of low solar + wind production. You can build battery storage to decrease the natural gas consumption, but how much battery storage do you have to build and how much can you reduce the natural gas consumption strongly depends latitude and local weather patterns.

https://solarbatteryatlas.electrotech-revolution.com/deploym...

France exports about 60TWh of electricity yearly for about 4B€.

Flamanville running at 100% generates 32TWh. It is amortized in 9 years. I'd say it's doing pretty okay even with its ballooning cost.