FWIW, Nuclear fuel reprocessing tech has been developed for that. I know the French version. It shrinks and stabilises the waste in the form of a special form of glass (of course radioactive). The entire waste generated since 50 years fits in a hangar waiting while politicians still argue about where to bury them for all eternity.

Please remember that burning coal also leaves behind dangerous and mildly radioactive waste, that's usually not protected in any way or form - it just sits there, washed away by rain and blown away by rain. Where I'm from(Silesia region of Poland) the ash hills are permanent feature of the landscape, and a short trip with a Geiger counter shows easily that they have higher radiation level than background. It's not very dangerous of course, but it's there.

On the other hand, actual nuclear waste is protected fantastically well, and it's not that difficult to store. We always had plans for ultra-long-term storage too, no? Deep underground in salt deposits so it would be protected against earthquakes and underground rivers.

I am not against nuclear per se, only against current nuclear technology. I think that if we want to stick to nuclear, we need to heavily invest in technology, that would be more safe and would not produce long term highly radioactive nuclear waste. If those issues are solved, I am all in.

Keeping radioactive waste far away from anyone who might be harmed by it, even for thousands of years, is a solved problem. We know how to bury stuff deep underground in a geologically stable region. Or if you prefer, throw it in a subduction zone.

As with most things nuclear-related, the real problem is NIMBY. If a country as large and sparsely populated as the U.S. can't agree on a place to bury nuclear waste, there doesn't seem to be much hope for others like France and Japan.

I am not convinced that it is a solved problem. How old are Egyptian pyramids? Yet there is a lot of stuff that we don't know about them. We are confident, that after 20 000 years, people will still know about nuclear waste storage facilities? Think about it: records could be lost, our language will be different. Why are we so sure that somebody will not dig it up?

The radioactivity of spent fuel decays exponentially. After a few hundred years, most of it is gone, although there is of course the danger due to the chemical toxicity, just like any other heavy metal deposit. Obsessing over what could happen if somebody digs it up after 10000 years is not anchored in reality.

It's funny that people are so worried about stuff like Pu-239, which is stored miles underground in steel containers and will be half of what it is after 24,000 years.

Meanwhile, "According to a recent model study the total anthropogenic mercury released into the ocean is estimated to be around 80,000 to 45,000 metric tons" [1]. We have spewed so much mercury that people are advised to eat less tuna because they have too much mercury.

And mercury is not radioactive. In other words, 24,000 years later, there will be 100% of the same mercury there is now! (Granted, some of them might have been removed from the ecosystem and deposited deep underground... I mean, just like how plutonium is stored right now.)

[1] https://en.wikipedia.org/wiki/Mercury_pollution_in_the_ocean

> The radioactivity of spent fuel decays exponentially

True, but it is still question of the half-life (i.e. plutonium)

> Obsessing over what could happen if somebody digs it up after 10000 years is not anchored in reality.

It is a reasonable concern, because we have never before in our history produced such toxic waste that lives so long. I don't know about you, but I do hope that Homo sapiens will survive next 10k years.

> > The radioactivity of spent fuel decays exponentially

> True, but it is still question of the half-life (i.e. plutonium)

To expand my statement, yes, spent fuel is a mix of different isotopes, some stable, and others unstable with different half-lives. The point being, if something is super-radioactive, then by definition it has a short half-life. And conversely, if something has a long half-live, it's per definition not as radioactive has something with a short half-life.

Thus, after 10k years, what is left is not that radioactive (to be more specific, after 10k years with a once-through cycle, spent fuel will have a radio-toxicity about 20 times that of natural uranium ore. Now, I'm not suggesting you should grind it into dust and sprinkle on your cheerios in the morning. But it's not any kind of civilization-ending toxicity either.

The idea that a future civilization will have the know-how to mine stuff 1 km underground, but somehow they have no clue about chemical or radio-toxicity just seems so absurd to me.

> It is a reasonable concern, because we have never before in our history produced such toxic waste that lives so long.

Citation needed. My guess would be that we have produced an unfortunately large amount of toxic waste, but the vast vast majority of that is not radioactive, and will thus never decay. Dig it up a million years from now, and it will be as toxic as it is today. The incredible energy density of nuclear fuel means that, in the end, the amount of nuclear waste is very small.

> I don't know about you, but I do hope that Homo sapiens will survive next 10k years.

I hope so too. In my mind, however, climate change, biodiversity loss, topsoil loss etc. rate far far higher as risk factors than a comparatively small amount of nuclear waste. In fact, by not deploying nuclear due to risks associated with nuclear waste, we significantly reduce our chances of dealing effectively with climate change, a much higher risk.

The fission products are mostly gone in centuries, but the actinides persist for much longer.

Protecting our distant descendants in case we destroy our own civilization and go back to the stone age is a niche concern at best, akin to the zombie apocalypse.

Even if there's an all-out nuclear war or runaway global warming, I think it's overwhelmingly likely that a sizable population will remain to safeguard our scientific knowledge. Instead of stone age, we'll probably end up with the situation in Alita: Battle Angel. In that case, I would be more worried about rogue groups digging up dangerous stuff on purpose than about anybody 20K years in the future.

Besides, we can read Egyptian hieroglyphs pretty well, and the Egyptians weren't even trying to create a writing system to last millennia. Armed with a much better understanding of linguistics and anthropology, I'm sure we can do a better job with our warnings signs.

Would this not become more of an issue if nuclear actually was embraced on a global scale? I mean, eventually we would run out of safe storage - the question would then be whether that would be in 20, 50, 100 years (and whether some better option would exist by then).

Disclaimer - I have no idea of the numbers involved so aware this may be a ridiculously trivial issue

One of the reasons we're producing so much radioactive waste is that we're too scared to reprocess spent fuel.

There's a lot of fissionable material remaining in the "spent" fuel that can be recovered, enriched, and thrown back into a reactor. The more cycles you put it through, the less waste you'll end up with. But the same process can also be used to make bombs, so we force everyone to keep the spent fuel in a bunker or something.

The deeper reason is that we don't need to reprocess spent fuel now, and that it's cheaper to wait.

A large portion of this problem was addressed by the Integral Fast Reactor concept developed in the late 1980s.