As an exercise for fun - I'm way behind on the project and should get back to it - I have been putting together, for my son, an exercise of designing a nuclear reactor that is almost entirely composed of the components of used nuclear fuel, other than the element thorium which is added to eliminate the need for uranium enrichment.
It has a fast neutron spectrum and is designed as a breed and burn device where Americium is the driver fuel, owing to its marvelous neutron multiplicity.
The problem with used nuclear fuel is not that there is too much of it but that there is not enough of it. We only have about 85,000 tons in the US, accumulated since around 1958. We definitely need more. One of the more valuable components is unreacted uranium, which accounts for roughly 95% of the fuel mass. Unlike natural uranium it contains the isotope 236U which has the interesting property of essentially of making enrichment of uranium very problematic and expensive, if even possible, to the levels used in nuclear weapons. It would be tragic to throw it away.
There is an isotope of selenium 79Se that people might be too lazy to put to use. It is an extremely low yield isotope less than 0.04 percent in the fission of 235U, less in the fission of plutonium and transplutonium nuclides, that might be expensive to use. I'd be willing to store the world supply in my basement, particularly since it always comes out diluted with the five stable isotopes of the element. It is a pure beta emitter generating no gamma radiation, safe if stored in a glass case in a museum in the future that would mock antinuke "concern trolling."
There is no such thing as nuclear waste. At least there shouldn't be. It's existence is psychological, not technical.
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