You neglect that they would have to be breeder reactors, or run out of fuel. And, that those would cost many times over what the renewables they could build, instead, cost. And would cost overwhelmingly more to operate than their neighbors' renewables. Those neighbors will be selling power at far below the nukes' base operating cost.
France would then have to choose between mothballing their reactors and buying neighbors' power, or taxing their own citizens to keep the breeders operating at their radically higher cost. The latter would be an unpopular choice.
In summer, of course, the reactors would all need to be shut down in any case, because there is not enough water in the rivers to cool them. France would be buying neighbors' power, then. They could continue, in fall, or spend big bucks to fire up the reactors again.
France would then have to choose between mothballing their reactors and buying neighbors' power, or taxing their own citizens to keep the breeders operating at their radically higher cost. The latter would be an unpopular choice.
In summer, of course, the reactors would all need to be shut down in any case, because there is not enough water in the rivers to cool them. France would be buying neighbors' power, then. They could continue, in fall, or spend big bucks to fire up the reactors again.
French tolerance for folly has limits.