What actually happens to nuclear waste?
Most of it is far less dramatic than the word suggests, and the genuinely difficult fraction is small in volume, enormous in longevity, and currently stored rather than permanently disposed of in almost every country.
The categories, which differ by orders of magnitude:
Low-level waste — gloves, clothing, tools, building rubble — is the great majority by volume and holds a tiny fraction of the radioactivity. It is compacted and buried in engineered near-surface facilities, and much of it decays to background within decades.
Intermediate-level waste, including reactor components and resins, requires shielding but not usually cooling. Typically encapsulated in cement or bitumen in steel drums.
High-level waste — spent fuel, and the liquid residue from reprocessing — is a few per cent of the volume and the overwhelming majority of the radioactivity. It generates heat and needs both shielding and cooling.
What happens to spent fuel now:
Cooling ponds at the reactor for years, where water provides both cooling and shielding.
Dry cask storage, in sealed steel and concrete containers, once cool enough — a robust interim solution good for decades.
Reprocessing in some countries, separating reusable uranium and plutonium from the waste, which reduces volume but is expensive and raises proliferation concerns.
Vitrification, melting high-level waste into borosilicate glass blocks that immobilise the radioactivity in a stable matrix.
The permanent answer is a deep geological repository — hundreds of metres down in stable rock or clay, with multiple engineered barriers. The science is broadly settled; the obstacle has been political, since siting requires the consent of a community asked to host something for a hundred thousand years. Finland's Onkalo is the first to reach operation, using a consent-based siting process that others are now copying.
The honest framing. The volumes are genuinely small — a country's entire high-level inventory can fit in a warehouse. The hazard is real and the timescale is unlike any other waste problem. Meanwhile it sits in casks, safely but unresolved.