Currently it's stored in nuclear waste bin, in pools in a few hangar. There is plan to store the in a geological stable hole, that we known that it won't move for a long time.

> The Nuclear Safety Authority has confirmed that the rock has not moved for several million years.

https://en.wikipedia.org/wiki/Meuse/Haute_Marne_Underground_...

Also, I'm not in the field, i just like to inform myself before having an opinon. Too many times there is lies spread about nuclear facilities.