The UK alone had the following inventory of nuclear waste as of 2022:

~1,470 m³ "high level" waste totalling ~14,000,000 TBq at year 2100. "High level" waste is that which generates enough heat to require specially designed and managed storage facilitates to prevent spontaneous fires etc.

~496,000 m³ intermediate level waste totalling ~1,000,000 TBq at 2100

~1,340,000 m³ low level waste totalling ~130 TBq at 2100

~2,750,000 m³ very low level waste totalling ~12 TBq at 2100. VLLW is considered safe enough to be disposed at landfill sites subject to certain special considerations. But not until the radioactivity drops below a certain threshold, of course - it still has to be stored at special facilities for many decades until then.

It's a pretty vast and costly problem even if you don't consider this a "vast quantity".

Source for these figures: https://www.gov.uk/government/publications/uk-radioactive-wa...