France is 551,695 km2
So 1/10,000th of france would be needed for 1GW
A 1GW reactor produces 9 billion kwh a year
France's entire electric requirement is 450 billion, so needs about 50GW, or 0.5% of France's surface area.
Based on those figures, space isn't a problem.
According to the parent poster, those 52 km² are needed for 1GW. France needs around 50GW, 50 times more power and area, ergo 2500 km².
It's the yellow dots here
France has about 1 million km of roads [1], lets assume at least 2m wide. That's 2,000 sq km.
How many of these roads can you see on this picture
[1] https://en.wikipedia.org/wiki/List_of_countries_by_road_netw...