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Comment by philliphaydon | Hacker News Reader

Just a random thought. What would happen if you dumped nuclear waste in a volcano? Would that burn it off or cause an explosion?

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You have the problem of potential eruptions sending it off everywhere.

Nuclear Waste has heavy elements that are dangerous specifically because they're radioactive. The heat might accelerate their half-life decay rate but it doesn't "burn" the atoms.

So tossing it in wouldn’t cause an eruption or burn off the radiation. But if the volcano erupted then it could send radiation everywhere.

Interesting.

Is research being done to try figure out safer disposal of nuclear waste?

Really the safest means of disposal is to bury it, but that is fraught with its own problems.

I did wonder if dumping waste in subduction zones has been looked at.

If the spent fuel were contained, you could first run it through a breeder reactor[0] to reduce volume by an order of magnitude or two. The remains are still highly radioactive, but now you have much less volume to deal with.

I assume that the waste in Chernobyl is largely/entirely distributed and contaminated with sand, dirt, other various debris, and thus probably couldn't benefit from that.

[0] https://en.wikipedia.org/wiki/Breeder_reactor#Waste_reductio...

The best solution is to bury it on land that is already more irradiated than any more added nuclear waste would make it. There is plenty of land like that.

What about launching it into space?

Rockets are not 100% reliable--having one carrying radioactive waste explode on launch would make for a really nasty mess to clean up.

Ultimately, the total volume of Radioactive waste ever created is tiny in the grand scheme of things. Burying it is not a technical problem. The problems are entirely political. This is also why breeder reactors don't make sense. They're trying to apply a technical solution to a political problem.

> Burying it is not a technical problem.

it is. the problem is that it needs to be stored way longer than any human is living. basically there are very few sites which might be able to withstand a timeframe so large without every polluting the environment. you know just burying is not enough, you need to be sure that no water or anything else might break your containments. it's probably impossible to do it and it's also not a good idea to think that burying it and forgetting about it is a good idea either.

Things that are radioactive for longer than human lifetimes are not very radioactive at all. The danger is more that they are still poisonous.

Finding places where you can control the groundwater isn't that hard. We have many candidates. Old salt mines are preferred because the salt slowly flows around the containers and entombs them. This is where the relatively small volume of the radioactive waste is a feature, you don't need a massive number of old mines to handle all of the waste. One or two would be sufficient.

Most of the concern about this is people demanding solutions that are grossly more complex and elaborate than the problem really demands. A political problem. Imagine if coal mines had to treat their tailings with the same level of care? They are similarly radioactive after a few years and just as poisonous, but we let them be dumped right into streams. Natural gas is extracted by pumping poisonous chemicals into the ground to break up rocks--greatly increasing the possibility of groundwater contamination. Imagine if they had to extract all of those chemicals back out of the ground and then store them someplace where they could be proven to never leak out again.

High level radioactive waste doesn't stay high level for very long by its very nature. This is why nuclear power plants have ponds where they store the hot stuff until it cools down enough for long term storage. After that they just have to be handled like any other nasty industrial chemical, plus some extra shielding to protect the workers from hitting their total yearly exposure limits too quickly.

> Things that are radioactive for longer than human lifetimes are not very radioactive at all. The danger is more that they are still poisonous.

good, so we take it out after 50 years and place it in your yard than? just kidding, but saying such things is stupid, the stuff is still highly dangerous even after > 1000 years, especially if the shielding gets blown away, people die from that. the fuel NEEDS to be on site for the first 10-20 years, since it's impossible to shield it good enough. after that it needs to be stored 100000 years at a minimum.

> Finding places where you can control the groundwater isn't that hard. We have many candidates. Old salt mines are preferred because the salt slowly flows around the containers and entombs them. This is where the relatively small volume of the radioactive waste is a feature, you don't need a massive number of old mines to handle all of the waste. One or two would be sufficient.

good idea. in germany we already found a salt mine: https://en.wikipedia.org/wiki/Asse_II_mine oh... wait.

btw. you can actually recycle some material, but that is expensive and is not done for all material, but it drain more billions of dollar for a single plant, most often it's easier to socialize the storage of the radioactive waste.

> High level radioactive waste doesn't stay high level for very long by its very nature

spent fuels is radiotoxic over 100000 years? I mean, that is long. of course for more money it can be reprocessed, reducing the long livity waste by a far margin and also not everything needs to be stored that long. it's still problem and down talking it does not help.

> Natural gas is extracted by pumping poisonous chemicals into the ground to break up rocks--greatly increasing the possibility of groundwater contamination. Imagine if they had to extract all of those chemicals back out of the ground and then store them someplace where they could be proven to never leak out again.

ok, because that's also bad it's ok to use another bad technology? heck coal is also bad it produces flying ash, way way more tones than all reactors in the world will produce over their lifetime. does it make the waste of nuclear better? no. is it good to point fingers on other technologies that are as bad? no. (to make it clear high level waste per 1000MW reactor is like 3m^3 (around a tonne) per reactor. of course it's not a lot compared to stuff that coal, mining (uranium gets mined, too and produces a shit ton of tailings) and gas, etc..., but a lot for the timeframe it needs to be stored)

After 50 years most nuclear waste is barely above background. I wouldn't want it in my yard because it's poisonous, not because it is excessively radioactive. Another way to think about this, uranium ore is in the water supply right now in some parts of the world. It's just about as radioactive as 100 year old waste and yet somehow people are managing to survive.

According to the Wiki that Asse II mine has not released radioactivity into the environment? It was maybe not the best choice given that the mine had been prone to flooding even when it was operational, but it's a manageable problem.

Dropping nuclear is exactly about using the other bad technologies. Renewables are slowly coming online to help, but for the most part you shut down a nuclear plant you open 4 natural gas plants in its place. Unless you are China, then it's 4 coal plants.

Once spaceX start launching from pads at sea I wouldn't be surprised if this was an option... load a rocket with really nasty stuff and fire it at the sun.

I bet Elon would do a massive discount for that.

Safest or cheapest? And on what time scale? Because the safest long-term means of disposal is to launch it into the sun, but that's prohibitively expensive and is short-term extremely dangerous (e.g. the rocket exploding or crashing shortly after lift-off).

I mean, you seem to be asking in earnest, so I'll answer. Still, the question is silly. Of course research is being done on this. Google is your friend.

Well I know we are researching how to /use/ nuclear waste. I believe that’s what one of bill gates projects is trying to do. But I donno if we have just decided burying it is it and that’s it.

The thing is, reusing nuclear waste is possible, but too expensive in the end, compared to renewables. I think there was 4 research reactor that did that in the world, and Russia launched a new one recently.

I still think nuclear must be part of the solution NOW (for an effect on CO@ in 2030 and on climate drift on 2050). Nuclear in 50 year will be too late. And i don't think nuclear is "the best", nor do i think that it isn't dangerous, nor do i think we should stop with renewables. Nuclear is a crutch and should be used as such.

"There are naive questions, tedious questions, ill-phrased questions, questions put after inadequate self-criticism. But every question is a cry to understand the world. There is no such thing as a dumb question." - Carl Sagan

I doubt the heat in volcano is enough that change anything at the nuclear level. Heat is just motion of atoms/molecules. The temperature has to be high enough for the atoms to undergo high-energy collisions.

We don't know any non-nuclear process that can accelerate the decay of nuclei, so that should not be possible to change anything about that!

There’s some experiments that indicate ultrashort and high energy laser pulses may accelerate decay but not a lot of interest has been allocated to it.

Ultrashort and high energy.. are you sure we're not getting into gamma rays and nuclear physics with that? I guess by definition we are, if it has an effect :)

"Burn it off"? What would that even mean? Burning is a chemical reaction. It doesn't alter nuclear processes that matter here.

The heat of the volcano wouldn't change anything. The problem is first that you can't guarantee it won't be carried on magma currents and be pushed above ground elsewhere, and second if it got stuck and didn't sink into Earth's core, you'd have a volcano dirty bomb just waiting for the next eruption. And you'd have no way of knowing if it got stuck or not.

Related: "Why Don't We Throw Trash in Volcanoes? " => https://youtu.be/Q1blQRrM4TA

Volcanic eruptions on the one hand and radioactive waste on the other are bad enough - no need to combine both.

Basically nothing would happen except that the radioactive materials would be dispersed among the environment.

When I was a kid I thought that launching nuclear waste into the sun was a decent idea. Now, not so much!

Into the sun would be fine.

Launches would be risky, though, and it's easier to send off to deep space instead. An out-of-the-solar-system orbit is cheaper energy wise than an into-the-sun one.

Right, the sun would obliterate anything that got close. The risks of the containers falling back to earth from a failed launch are significant.

Launching into deep space reminds me of the drill instructor in the game Mass Effect: https://www.youtube.com/watch?v=6q1IaWLsyrQ

It would be a pretty good idea if it didn't require such an insane amount of delta-v to deorbit a payload into the sun.

We just need to lift it there with a space elevator and then nudge it into the sun.

And then in a few thousand years we will be kicking ourselves for incinerating incredibly valuable resources.

It's just being converted to solar :)

It is less delta-V to launch something out of the solar system than it is to drop it into the sun.

Assuming you're not worried about nuclear waste leaving our solar system and becoming a problem for others, it makes absolutely no sense to launch it into the sun.

> becoming a problem for others

That seems a bit optimistic of a problem to have. Space is incredibly huge. For someone to accidentaly bump into it would have odds so huge I don't even know how to aproximate it.

There's no such thing as 'nudging' it into the sun. If you don't push hard enough, it will enter an orbit that coincides with earth's. And to push it hard enough you basically have to get it going away from earth at the speed earth orbits around the sun, which is quite fast.

Anything less, and it will be in an orbit that floats close to the sun then floats back up towards earth, more or less forever.

I think that we're going to need a bigger space elevator, then.

wouldn't you only need to deorbit if you "missed"? it's not like we're trying to safely land on the surface of the sun. we don't need it slow down at all, just aim straight for the middle and accelerate in.

As Earth is in orbit around the sun, everything launched from Earth automatically is also in orbit around the sun. To go into the sun, you need to deorbit from that orbit. Earth's orbit around the Sun has an orbital speed of about 30 km/s, so you need to cancel that to drop into the sun.

It doesn't have to get there fast. So what would the effect of putting up solar sails to create some drag to slow down? Wouldn't need heavy fuel to generate delta-v. Would the expense of a system to deploy/unfurl a solar sail cost more than fuel powered thrust?

Aside from the practical concerns with solar sails, there's a fundamental problem with using them to get to the Sun. To lower your orbit, you need to exert thrust in the retrograde direction (directly opposite to the direction you're going). However, that's perpendicular to the direction of the sunlight you receive, so a solar sail cannot generate any thrust in that direction!

What about using mass drivers instead of chemical rockets?

Theoretically, sure. Practically we've entered science fiction territory here.

Yeah, I figured we did once we started talking about solar sails and space elevators.

Up next is just let the thing hang out in orbit around the sun at 1AU waiting for one of these "near miss" asteroids to come wizzing by so we can "catch" it with a net and let it drag our trash to the inner reaches of the solar system.

once you've negated the delta-v, reel in the sails or detach them or whatever. at that point, Sol's gravity should do the rest. i'm sure some smart people with slide rules could determine when to do it to not be influenced by Venus/Mercury on the way in.

> once you've negated the delta-v

My point is that you can't cancel out the velocity of your orbit around the sun using solar sails.

So if you had the sail at a 45 degree angle to the sun, bouncing the photons forward to your orbit, wouldn't that eventually slow you down? Or do you get pushed outward into a slower orbit at the same time and cancel it out?

It's all a moot point anyway since solar sails are so ridiculously impractical that this would basically never work in real life regardless.

Mercury or Venus would be a better easier and cheaper alternative if the plan is to bury this garbage. Even the moon could be a better storage for the next two thousand years than anywhere in the earth.

You could put it near a subduction zone and wait for it to be pushed under a neighboring tectonic plate.

Maybe the heavy atoms would sink into the mantle.

There have been serious proposals to put a bunch of nuclear waste in a tungsten sphere, add a few sensors, and use it as a probe into the earth as it melts through the mantle.

Seems like a silly idea, but thinking about it more deeply I'm not so sure. Uranium is almost 7 times as dense as even the densest magma, so it _should_ sink in theory. The only issue I can think of is that "maybe" isn't good enough when you're talking about risking a large amount of radioactive waste getting spread out over a large area in a volcanic eruption if it turns out you're wrong. But if we could figure out a way to do it reliably... maybe?

Another potential issue: is getting rid of nuclear waste _permanently_ really such a good idea? What if we discover some other use for it in the future?

Volcanoes are places where magma upwells to the surface, so they'd have to be so heavy they were able to sink against that upward flow. Very unlikely.

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