We can potentially reprocess used nuclear fuel, but that has so many problems.

The reactors are much more advanced designs, and the US and much of the world has been focused the opposite direction: on very simple, very safe, lower cost designs. Making a fast neutron reactor is just a different class of beast, and it's unclear where the appetite is for it. (Which is a shame.) Japan, China, India, and Russia are the only countries to have started new breeder reactors projects since Franc'es last reactor Superhenix in 1985.

Most breeder reactors use a reprocessing mechanism that is somewhat akin to the enrichment used for weapons. It's goal is to extract the good & enriched stuff & leave the rest of the fission product out (which still have hundreds of years to be dealt with). There's still justifiable hesitancy about developing such technology further. Even if we feel like we can use it safely in X Y and Z countries, once the technology becomes more proven (particularly if it can be shown to be cost effective) it's hard to imagine it won't become more available, and that has a real & scary risk.

Ask yourself how many of the above countries that started breeder reactors do we want making new nuclear weapons? And note how many have kicked out nuclear weapons inspectors (Russia, China).

One of my favorite candidate designs was the Integral Fast Reactor (https://en.wikipedia.org/wiki/Integral_fast_reactor), began in 1984 as a faster fast reactor which was considerably safer by default, and which was capable of a lower-refinement (lower proliferation concern) burning of already spent fuel (including a wide range of medium-lived/longer-lived transuranic wastes). But almost all indicators are that we try for simpler & dumber designs, not to improve & refine what we could do.

I also think it's a huge disservice only identify short half-life products as dangerous. Yes they have the most immediate threat, but we generate plenty of other wastes that are severely scary, particularly among the transuranics, and plenty of even the "low" nuclear wastes will quickly ruin an area & spread if mistakes happen. The variety of different nuclearly active chemical wastes we have to deal with is vast (those pesky transuranics). I'd love to be talked down here some, I think this is one place I'm best able to be convinced with good science, but my reading of information like https://en.wikipedia.org/wiki/Breeder_reactor#Waste_reductio... is that there is just so much to be dealt with, such a pesky variety. And yes fast reactors help a lot here, if we can deploy them at scale effectively, but again I just question whether on a cost basis that will happen.

I agree with you in principle that nuclear has amazing potential to be handled well. But in fact, most of the world takes the shortest route they can & thinks nothing of how much or what kind of waste is generated. It's a network externality, foisted off onto the government to deal with. Even in France, the one beacon of breeder reactors, there's been scant investment in improving iterating or refining what mechanisms they have; continuing to use one centralized PUREX refining center to do most of the work. Meanwhile we have few positive indicators elsewhere about good nuclear. IFR derived designs like PRISM, S-PRISM and Versatile Test Reactor have repeatedly stalled.

To provide some counter to my own general thread, Japan has shown again and again a willingness to try & try hard that I respect. They recently started working with TerraPower on a PRISM/IFR based design that could potentially go somewhere. But this is a faint ray of hope in a gloomy low-tech unglorious nuclear landscape. https://neutronbytes.com/2022/02/03/terrapower-teams-up-with... https://news.ycombinator.com/item?id=35430993