Technically yes if you have an entire fleet to both spread the load following across and their manage their fuel cycles since they get less flexible the further into a fuel cycle a reactor is.
Economically? Load following with nuclear power means an even worse business case than running at 100% 24/7. And nuclear power is already a laughably bad business case when running at 100%.
You don't need to change fuel cycles to reduce the output of a nuclear plant. You can accomplish it by more aggressively cooling the water in the steam turbines, effectively wasting heat (and thus generating less power).
Nuclear is a bad business case compared to a fossil fuel grid. Solar and wind backed by fossil fuels are a better business choice, too. But when it comes to a fossil-fuel free grid, it's the only viable option if you don't have a big source of hydropower nearby. Batteries can't deliver the required storage capacity. Remember, the world uses 60,000 GWh of electricity per day. And as transportation and industrial uses of fossil fuels are electrified, that'll increase.
What are the other storage options? Besides batteries and hydroelectric, there's only prototype technologies that haven't seen any significant deployment at scale. Compressed air, hydrogen, and power to gas have been tried but no at anywhere near grid scales.
Five years ago batteries weren’t anywhere near grid scale either. Arguably they still aren’t. That doesn’t mean we should not consider them when talking snot the grid in 2040.
Sure. But we also shouldn't assume they will be successful at grid-scale either. Planning a grid assuming that some future storage technology will be a silver bullet that solves grid storage is a massive gamble.
Hydroelectric storage is the only grid-scale energy storage system available to us, and it's geographically dependent. And the places that are suitable for hydroelectric storage usually don't need it because they can just generate electricity via hydropower anyway. Until your hypothetical breakthrough in power-to-gas or giant flywheels actually happens, this is the state of grid storage.
Economically? Load following with nuclear power means an even worse business case than running at 100% 24/7. And nuclear power is already a laughably bad business case when running at 100%.