Breeder reactors can utilize uranium-238 as well as uranium-235, effectively expanding the supply of fuel 100-fold.
Uranium depletion can theoretically be avoided by extracting uranium from the sea, which is constantly replenished by erosion (rivers).
Four projects seem to have succeeded, for example, the Waste Isolation Pilot Plant in USA is already operating and began accepting military transuranic waste in 1998. Two other projects, the planned final storage facilities at Gorleben in Germany and Yucca Mountain in the USA, were cancelled or put on hold indefinitely.
The extremely long lifes of waste are usually obtained due to a misapplication of a rule of thumb for short-lived isotopes, which says that a sample is no longer radioactive after 10 half-lifes.
This technology was experimentally demonstrated in Japan, but no large scale facility was built so far.
In addition to uranium, thorium can also be used as a nuclear fuel in future nuclear reactors.
These were the two repositories for intermediate and low-level nuclear waste (e.g.
not spent fuel) that were built in Germany: Asse II and Morsleben.
The method puts the waste deep underground in a geologically stable rock formation, with several layers of defence against water intrusion.
Several such repositories have been built, but the results have been a decidedly mixed bag: out of six such repositories that went into operation, two have since turned out as failures.