Base load is an obsolete concept. A renewables-heavy grid simply doesn't work that way.

Renewables like solar have a per-MWh generation cost of zero. You literally have to make the electricity price negative before it makes sense for the operator to shut it down. Their profitability depends only on the average electricity price: the high market price during the winter makes up for the near-zero market price during the summer.

In a free electricity market there is absolutely zero demand for a power plant which generates a constant amount of power and acts as the "base supply". With dirt-cheap renewables its capacity simply isn't needed during the summer and its nonzero running costs makes it unable to compete. What is needed instead is a peaker plant which can supplement renewables, and which is profitable when it operates only during low-sun low-wind "dunkelflaute" winter weeks.

Nuclear is fundamentally incompatible with this. It is the most expensive form of electricity generation and its costs are dominated by the need to pay back a massive construction loan. In a free market a nuclear power plant would only be able to operate for a few weeks per year, which instantly kills its business case.

Want nuclear? Then you'll have to accept that it will require huge government subsidies, and that during high-supply moments you'll be turning off free renewables to make space for expensive nuclear.

If anything, one could say that renewables will be the new base load supply. The real question is: who will be doing the peaking?