> That's not possible for nuclear which provides base load - in fact they need to be shut down during heat waves

Google "load following nuclear" and also read the article in Wikipedia [0]. That will help stop false information. Summary: Nuclear power plants in France and in Germany operate in load-following mode and can go from full baseload to nearly "running on idle" in 15 minutes if needed.

[0] https://en.wikipedia.org/wiki/Load-following_power_plant#Nuc...