Where used nuclear fuel is kept
Almost all of it is sitting where it was made. Spent fuel goes first into a pool at the reactor for several years, then into dry casks of steel and concrete on a concrete pad, usually within the plant's own fence. A handful of countries have built centralised stores instead. Nobody anywhere has moved commercial spent fuel into permanent disposal, so every tonne ever discharged from a power reactor is still in storage somewhere, seventy years into the industry.
Fuel leaves the core intensely radioactive and thermally hot, and it stays hot. That is decay heat, and it is why the first destination is always water: a pool provides cooling and shielding at the same time, and the fuel stays there for several years until its heat output has fallen enough to be handled by air alone.
After that it can move into dry storage. A cask is a steel canister inside a concrete overpack, sealed, sitting outdoors, cooled by convection with no pumps and no power. This is genuinely passive, which is why dry storage is the least controversial part of the back end technically and the most consequential politically: it works well enough that deciding what comes next can be deferred, and almost everywhere it has been.
Centralised stores are the exception rather than the rule. Sweden's Clab holds the country's entire inventory in one rock cavern. The Netherlands built HABOG to last a hundred years and painted it orange, on the theory that a building people can see is harder to forget about. Ukraine commissioned a central store in 2023, during a war, specifically to stop shipping its used fuel to Russia.
Everywhere else, the material is distributed across as many sites as the country has reactors. That is a very different problem from a single repository, and a harder one to supervise over the timescales involved.
The United States is the extreme case, holding the largest inventory in the world with no disposal route at all. Its federal government is contractually obliged to collect utilities' spent fuel, has never collected any, and pays damages for the failure every year.
Storage is not capacity-constrained. Casks can be built to order, pads can be poured, and licences to expand on-site storage are routinely granted. The constraint is that interim storage is defined as temporary and is being used as though it were permanent. Every year of deferral adds inventory to sites that were never chosen for it, chosen instead for their access to cooling water and their distance from cities, which are not the criteria you would use to select a place to leave something for a century.
Facilities
Sources
- SKB
- World Nuclear News, Holtec cancels plans for New Mexico interim storage facility
- World Nuclear News, US Supreme Court rules on interim storage facility case
- World Nuclear News, Japanese used nuclear fuel store starts operating
- World Nuclear Association, Storage and Disposal of Radioactive Waste
- COVRA
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data