An array of small modular [nuclear] reactors (SMRs) could be set up to switch parts of the array on and off over the course of the day to scale with load. Small plants have shorter ramp-up and ramp-down times, as they move around smaller amounts of working fluid, and power lighter turbines which thus have proportionately higher friction/lower inertia.

Of course, this is a lot less efficient than having one big nuclear reactor pumping huge turbines; but it’s possibly more efficient than other forms of peak-load generation, which is the key issue.

Plus, any given individual SMR would produce a low-enough wattage to be able to reasonably divert/“dump” power from it into an practical-to-construct-anywhere sink or battery (e.g. building-sized pumped storage, rather than huge dam-sized pumped storage) for handling ramp-down discontinuities.

As long as we are going there, backing a traditional nuclear power plant with a reservoir for pumped storage would work as well. But the land needed for such is immense and limited (though great for recreation opportunities). Nuclear could also be coupled with a desalinization plant that would use excess energy to produce clean water for later use (but there are other challenges there).

If liquid hydrogen fuel was ever useful, it could produce that with excess capacity also (but again, other issues).

There's lots of things to do with extra electricity, it's just a question of whether or not it's economical. Here in California, for example, I could imagine the excess being used to opportunistically desalinate water and refill reservoirs. If water and emissions were priced appropriately, it might be worthwhile? It's not exactly a battery, but it's a way to make overbuilding more palatable.

Alternatively if the grid is unreliable, end-use customers will install their own batteries and generating capacity. Voila, problem solved on someone else's dime!

France is a nice counterexample to this. Nuclear is usually used as a buffer for needs and production variations.

In fact, modern Combined cycle natural gas plants are less controllable than nuclear ones.

(That being said, given that the cost of a nuclear plant is mostly independent from its energy output, why would you build wind farms if you already have nuclear plant? Except for political reasons of course)