Good news: nuclear costs the same to run at max output as it does idle! No change in fuel costs.

Other good news: solar and wind is trivial to curtail at the press of a button. And very cheap to deploy far more than needed on a day with perfect conditions.

Thus the obvious solution is keep your nuclear running at full load 24x7 and vary the rate at which you feed solar and wind into the grid on those days of optimal production. Idle solar is nearly free, which is one of its largest benefits! This way you have enough solar and even short term battery to meet peak daytime demand even on relatively cloudy days, and don’t need to overbuild your nuclear fleet. But you still get seasonal energy storage in the form of extremely dense nuclear fuel.

Nuclear compliments renewables quite well if you remove the fake financial incentives of “I must be allowed to be paid dump every watt possible into the grid at all times even if not needed, but cannot be called on to produce more energy when required”. Solar produces the least valuable watts. Nuclear the most. So use the cheap stuff whenever possible but fill it in with the expensive reliable source when needed.

That or you’re just gonna be backing renewables with natural gas. Which is of course cheaper, but not all that green.