Okay I think you missed the point a little.yes you keep the nuclear power plant on all the time. Which is fine if it’s night and you need the power. But on a sunny day you end up with a reactor producing power that has nowhere to go.

You can sell the excess power to some extent. Store it by pumping water into reservoir. And a lot of what end up happening is, you dissipate the excess in huge resistors as heat.

But I agree it’s not ideal as a solution but it’s better than having brownout because there are too many clouds.