The answer is you don't scale nuclear up or down, it's a silly waste of time and effort to even think about it. The fuel costs are effectively a rounding error, so running at 100% 24x7 is the only way to ever think about how nuclear should operate.

If you are going to curtail, you curtail other sources including solar and wind.

Nuclear fits quite well for the baseload you need. It's more expensive, but if you are going to need X capacity 24x7 and build nuclear, you simply build enough to provide just that plus perhaps a few extra for redundancy when another one goes offline. Then use gas peakers for the "oh shit" days difference between what nuclear is providing and solar was expected to but could not.

I don't understand the fascination folks have about nuclear not being able to following the grid. They don't need to, since they only ever remotely make sense when operated 24x7 at 100%. If you always have 1TW of grid usage every night during your lowest usage period - build that much nuclear as your starting point and figure out the rest from there. Nuclear's share of the total mix should be a straight line on a graph outside of plant shutdowns for maintenance.