France is a net importer. I am not sure what exactly you mean by "France is one of the biggest exporters" though.

Here a graph that shows "total energy used in the country minus its production of energy", which shows that France that mostly produces nuclear energy consistently requires more energy than it produces.

https://www.theglobaleconomy.com/france/Energy_imports/

Even though that wasn't really what I am talking about. The reality is that France frequently has to shut down many of their reactors, which causes them to for longer periods of time require energy from Germany.

The reason for that is that for example in July 2022, 29 of their 56 nuclear plants were offline due to outages. Given that as you the majority of what France produces is nuclear energy, this is a big problems. These offline plants still require energy for cooling. So if other countries didn't provide energy France would have had a blackout. A lot of that is evidently cold by climate change and heat (these problems mostly happen in summer), but at the same time France for example at the end of 2021 had issues and needed to import energy for heating.

This is not to be pro-gas or coal at all. I think they should be abandoned as quickly as possible for many reasons, CO2, pollution both at energy production as well as fuel production, limits on availability, etc. This is to say that just everyone switching to to nuclear energy isn't a magical fix.

There is a strong need for mixes, both in how energy is produced and saved. And when I say saving, I don't mean batteries, but storage plants, some for long time storage like pumped storage hydroelectricity, and various types with typically lower storage, but quicker response times for spikes to prevent outages. Cause then one can actually make use of less consistent energy sources. Short-term and long-term storage work. And the more of those you have to more stable your energy grid will be, regardless of whether you use nuclear power or other power. And you won't have to shut down plants so quickly, because you overproduce at certain times of the day, be it for solar energy or less demand at night, for nuclear energy.