Not that much, at its peak it made up 25% of their power, I think we used to be around 20% and are down to 16% at the moment. France is an outlier.
I think the choice to shut down their nuclear fleet was a mistake, once they're up and running they're a very good generation system*. The choice to keep shutting it down with the gas crisis is very strange.
*Unless you have a natural disaster, in which case a rather unnatural disaster can follow.