DOesnt matter how much there is…its highly radioactive and stays that way for many many years…the idea of storing it in a “mountain bunker” or similar just seems like a bad idea to me and others have agreed.
Permanent storage underground in U.S. had been proposed at the Yucca Mountain nuclear waste repository, but that project has now been effectively cancelled - the permanent disposal of the U.S.'s high-level waste is an as-yet unresolved political problem.
Who knows what other countries are doing.
So yeah it is a problem. Not on a volume level since like you say, not much waste is actually produced. Its just radioactive and its a long term problem.