Scrutable

Posted: **Wed Oct 20, 2021 10:13 am**

A novel proposal:

https://mobile.twitter.com/ArthurB/stat ... 6244749313

Posted: **Thu Oct 21, 2021 11:17 pm**

not sure it would work with low level nuclear waste

Posted: **Thu Oct 21, 2021 11:56 pm**

I'm pretty sure it wouldn't work with high level waste either, with the ball melting the earth and creating a weak spot for magma to erupt from, possibly launching the ball back into the atmosphere. And probably melting the tungsten at some point in the process.

If the exterior of the ball can get to the 1300 C needed to melt rock at the surface while surrounded by air, I suspect it'll get hot enough to build pressure inside and also soften the tungsten significantly when it's surrounded by 1300 C rock.

Posted: **Fri Oct 22, 2021 1:38 am**

dyqik wrote: Thu Oct 21, 2021 11:56 pm I'm pretty sure it wouldn't work with high level waste either, with the ball melting the earth and creating a weak spot for magma to erupt from, possibly launching the ball back into the atmosphere. And probably melting the tungsten at some point in the process.

If the exterior of the ball can get to the 1300 C needed to melt rock at the surface while surrounded by air, I suspect it'll get hot enough to build pressure inside and also soften the tungsten significantly when it's surrounded by 1300 C rock.

Tungsten does have a very high melting temperature of ~3400°C but is also a good thermal conductor.

As well as potentially creating man-made volcanoes, I'm concerned with what size of balls they are intending to use - tungsten's fairly rare and has a lot of useful purposes at the moment - why waste good tungsten on this when vitrification and storage are available and known to work (for a given value of work, which appears to be long enough for the experts not to be worried).

Posted: **Fri Oct 22, 2021 1:41 am**

Martin_B wrote: Fri Oct 22, 2021 1:38 am
dyqik wrote: Thu Oct 21, 2021 11:56 pm I'm pretty sure it wouldn't work with high level waste either, with the ball melting the earth and creating a weak spot for magma to erupt from, possibly launching the ball back into the atmosphere. And probably melting the tungsten at some point in the process.

If the exterior of the ball can get to the 1300 C needed to melt rock at the surface while surrounded by air, I suspect it'll get hot enough to build pressure inside and also soften the tungsten significantly when it's surrounded by 1300 C rock.
Tungsten does have a very high melting temperature of ~3400°C but is also a good thermal conductor.

It also has young's modulus at 2400C that's 2/3 of that at room temperature. Finding the yield strength temperature is a bit harder though.

One problem is the nuclear waste probably doesn't have a high thermal conductivity, and probably doesn't have such a high melting, or possibly boiling, point

Posted: **Fri Oct 22, 2021 1:48 am**

dyqik wrote: Fri Oct 22, 2021 1:41 am
Martin_B wrote: Fri Oct 22, 2021 1:38 am
dyqik wrote: Thu Oct 21, 2021 11:56 pm I'm pretty sure it wouldn't work with high level waste either, with the ball melting the earth and creating a weak spot for magma to erupt from, possibly launching the ball back into the atmosphere. And probably melting the tungsten at some point in the process.

If the exterior of the ball can get to the 1300 C needed to melt rock at the surface while surrounded by air, I suspect it'll get hot enough to build pressure inside and also soften the tungsten significantly when it's surrounded by 1300 C rock.
Tungsten does have a very high melting temperature of ~3400°C but is also a good thermal conductor.
It also has young's modulus at 2400C that's 2/3 of that at room temperature. Finding the yield strength temperature is a bit harder though.

One problem is the nuclear waste probably doesn't have a high thermal conductivity, and probably doesn't have such a high melting, or possibly boiling, point

"Nuclear waste" is also a pretty vague term. Technically, the slightly irradiated water used to wash the clothes that workers wear at Sellafield is 'nuclear waste', but I don't think it's worth encasing in Tungsten balls, and wouldn't have the decay energy to heat them up to 1300°C!

Posted: **Fri Oct 22, 2021 6:48 am**

CofI alert: I recently moved into the nuclear decommissioning sphere professionally.

Annoyingly, a couple of weeks ago I was idly pondering the possibility of making a "nuclear torpedo" of the heat producing stuff and dropping it into the ground somewhere with benign geology to sink through the crust into the mantle, but figured the unknowable risk of accidentally creating a volcano would make it impossible to do anywhere. Imagine the fracking debate if it could in theory make a volcano rather than an earthquake. Now I find that I was beaten to the idea a decade ago by someone who thought it worthy enough to write a whole paper. Huh.

This approach would only be viable* with the High Level Waste (HLW), which is defined as heat producing, and in reality would only work on a subset of that. Intermediate Level Waste (ILW) and lower don't produce heat so this won't work on them. Sure you might be able to pack some ILW into the sphere, but not much or you'll end up with a sphere too big to heat itself sufficiently. Also we have orders of magnitude more ILW than HLW to deal with.

*big asterisk. HLW is mostly spent fuel, which is significantly more radioactive than new unused fuel, due to the fission fragments contained within from the fissioned Uranium or Plutonium nuclei. The fission fragment isotopes have half lives ranging from the very brief to the decades and multiple millennia, but we can put the spent fuel in ponds to keep cool for 3-4 decades for the shorter half life fragments to decay into less active isotopes and the whole fuel rod will no longer be heat producing to the extent that it needs water cooling, and air cooling from then on would be sufficient. This means that for putting in a sphere and producing enough heat to melt its way through rock, there is a time window defined I guess by your piece of HLW's heat production/time curve, and how much insulation you expect the rock to provide and so whether the sphere can reach the required temperature to melt through rock. My suspicion based on zero calculations is that much of the legacy HLW is probably too cool.

Posted: **Fri Oct 22, 2021 8:09 am**

what if you made a controlled volcano* and just chucked it in?

*ie what is a controlled volcano and can you make mini ones

Posted: **Fri Oct 22, 2021 12:11 pm**

plodder wrote: Fri Oct 22, 2021 8:09 am what if you made a controlled volcano* and just chucked it in?

*ie what is a controlled volcano and can you make mini ones

A volcano is by definition something that from time to time erupts ground material in a temporary liquid state from below through a vent or fissure onto the surface. Mostly lava, but there are also mud volcanoes. The eruption is generally driven by high pressure resulting from sufficient material getting very hot and going through phase changes. And a major factor can be that as the pressure is released by the opening of the volcanic eruption vent or fissure, so gases are released from solution and expand explosively pushing material out of the volcano.

So if you drop something into a volcano, it may well erupt it back out again. You would only be able to drop it in if it had an open lava lake to drop it into. There are only a few volcanoes that have persistent lava lakes - Erta Ale in Ethiopia, Volcán Villarrica in Chile, for example. Though some others can have a temporary lava lake during eruptive periods.

The fact that the item you have dropped in is denser than the liquid you dropped it into may be insufficient to ensure it goes downwards rather than upwards. What is the upward flow rate of the erupting liquid? What is the effect of the gas release explosions? I think you'd want to get it to sink below any point where gas release explosions are occurring before any such explosion occurs, or it will probably be exploded back out again. Are volcanic pipes from the lava lake at the vent down to the magma chamber in fact nice wide pipes of all liquid material, such that a large item dropped into that pipe would be able to sink into the magma chamber without getting stuck on constrictions and multifurcations in the pipe on the way down?

You can put a rock in a pan of boiling water and it is dense enough to drop to the bottom and stay there despite the boiling. But great boulders are moved by floods, when the flow rate and quantity of the water movement is sufficient.

But perhaps you can choose your geology and find a volcano with the perfect properties, that has low dissolved gases in its rock, and and a nice broad pipe down to the magma chamber. Then provided the nuclear waste container was able to survive being in a lava lake and dense enough to overcome the upwards flow, it would be able to sink into the magma chamber, and down to the bottom of that, against the upward flow of the lava. But in such a location, would the container have the integrity to survive a caldera collapse on top of it? Can we endure that after earthquakes that tend to happen around volcanoes, causing major movements of material within the volcano, future eruptive events won't explode it out again?

Posted: **Fri Oct 22, 2021 12:33 pm**

IvanV wrote: Fri Oct 22, 2021 12:11 pm
plodder wrote: Fri Oct 22, 2021 8:09 am what if you made a controlled volcano* and just chucked it in?

*ie what is a controlled volcano and can you make mini ones
A volcano is by definition something that from time to time erupts ground material in a temporary liquid state from below through a vent or fissure onto the surface. Mostly lava, but there are also mud volcanoes. The eruption is generally driven by high pressure resulting from sufficient material getting very hot and going through phase changes. And a major factor can be that as the pressure is released by the opening of the volcanic eruption vent or fissure, so gases are released from solution and expand explosively pushing material out of the volcano.

So if you drop something into a volcano, it may well erupt it back out again. You would only be able to drop it in if it had an open lava lake to drop it into. There are only a few volcanoes that have persistent lava lakes - Erta Ale in Ethiopia, Volcán Villarrica in Chile, for example. Though some others can have a temporary lava lake during eruptive periods.

The fact that the item you have dropped in is denser than the liquid you dropped it into may be insufficient to ensure it goes downwards rather than upwards. What is the upward flow rate of the erupting liquid? What is the effect of the gas release explosions? I think you'd want to get it to sink below any point where gas release explosions are occurring before any such explosion occurs, or it will probably be exploded back out again. Are volcanic pipes from the lava lake at the vent down to the magma chamber in fact nice wide pipes of all liquid material, such that a large item dropped into that pipe would be able to sink into the magma chamber without getting stuck on constrictions and multifurcations in the pipe on the way down?

You can put a rock in a pan of boiling water and it is dense enough to drop to the bottom and stay there despite the boiling. But great boulders are moved by floods, when the flow rate and quantity of the water movement is sufficient.

But perhaps you can choose your geology and find a volcano with the perfect properties, that has low dissolved gases in its rock, and and a nice broad pipe down to the magma chamber. Then provided the nuclear waste container was able to survive being in a lava lake and dense enough to overcome the upwards flow, it would be able to sink into the magma chamber, and down to the bottom of that, against the upward flow of the lava. But in such a location, would the container have the integrity to survive a caldera collapse on top of it? Can we endure that after earthquakes that tend to happen around volcanoes, causing major movements of material within the volcano, future eruptive events won't explode it out again?

by "making a controlled volcano" I meant engineering a structure that gave us access to magma in a controlled way. A lined shaft, a lid, an airlock etc.

Posted: **Fri Oct 22, 2021 12:42 pm**

Kīlauea is probably benign enough most of the time that you could just chuck stuff in when it's in a moderately active mode.

However, it's probably not hot enough to do much to spent fuel rods, although I'd have to check melting points and temperatures.

Most importantly, volcanoes by definition are pushing lava outwards, so all those radioactive atoms are coming straight back. Density probably isn't important, because lava is pretty viscous unless it's very hot and active, when it'll be coming back at higher pressure.

Posted: **Fri Oct 22, 2021 1:16 pm**

OK, a shaft, a lid, an airlock and a weight to attach to the waste.

Presumably with geo-thermal we've already kind of got the tech kind of.

Posted: **Fri Oct 22, 2021 1:20 pm**

plodder wrote: Fri Oct 22, 2021 1:16 pm OK, a shaft, a lid, an airlock and a weight to attach to the waste.

Presumably with geo-thermal we've already kind of got the tech kind of.

Geothermal generally pumps water or other working fluid down wells to hot solid rock (much below 1000 C), and then back up to the surface. There's no liquid state magma involved, and it's nowhere near as hot as a volcano itself. In the last big Kīlauea eruption, the geothermal plant had to shut down because things were too active.

Posted: **Fri Oct 22, 2021 1:37 pm**

There's a startup that wants to build little reactors that run off of the 'hottest' waste https://www.cnbc.com/2021/06/28/oklo-pl ... waste.html

I don't know what portion of the population will be comfortable with this from a safety perspective.

Posted: **Fri Oct 22, 2021 1:52 pm**

As far as I can gather the temp inside a nuclear reactor is also about 1000C (I might be completely wrong about this) but it looks like if we can safely make nuclear waste we can also safely build a magma elevator bin fire.

Posted: **Fri Oct 22, 2021 1:56 pm**

plodder wrote: Fri Oct 22, 2021 12:33 pm by "making a controlled volcano" I meant engineering a structure that gave us access to magma in a controlled way. A lined shaft, a lid, an airlock etc.

You said, "what is a controlled volcano", so I assumed you didn't know what you meant by it. So I therefore set out to describe some desirable properties of a volcano you would require as a minimum, to try and create.

Can you drill into magma without it erupting on you? Drilling into magma has only happened a handful of times, usually unintentionally, and no surface eruptions occurred. At Krafla in Iceland they unintentionally drilled into some. It was only a small pocket of magma. They did successfully line the borehole and turn it into a geothermal source. They are now trying to repeat the process deliberately.

At Puna Geothermal Plant in Hawaii they drilled into some magma in 2005. It flowed into the borehole, solidified and blocked it. So they had to redrill several times to try and avoid the magma.

If you want to have access to a lava lake you can drop your nuclear waste into, you are going to need to find something on a different scale from these little pockets of lava they drilled into, and the experience of doing that might be a bit different.

Posted: **Fri Oct 22, 2021 1:59 pm**

dyqik wrote: Fri Oct 22, 2021 1:20 pm
plodder wrote: Fri Oct 22, 2021 1:16 pm OK, a shaft, a lid, an airlock and a weight to attach to the waste.

Presumably with geo-thermal we've already kind of got the tech kind of.
Geothermal generally pumps water or other working fluid down wells to hot solid rock (much below 1000 C), and then back up to the surface. There's no liquid state magma involved, and it's nowhere near as hot as a volcano itself. In the last big Kīlauea eruption, the geothermal plant had to shut down because things were too active.

How about we bury the waste in a way that doesn't sink, then use the heat in the same way as geothermal?

Posted: **Fri Oct 22, 2021 2:29 pm**

just spit-balling, obvs. The end technology would likely be used for something far more fabulous and completely unexpected anyway. Let's not be naysayers.

Posted: **Fri Oct 22, 2021 2:49 pm**

monkey wrote: Fri Oct 22, 2021 1:59 pm
dyqik wrote: Fri Oct 22, 2021 1:20 pm
plodder wrote: Fri Oct 22, 2021 1:16 pm OK, a shaft, a lid, an airlock and a weight to attach to the waste.

Presumably with geo-thermal we've already kind of got the tech kind of.
Geothermal generally pumps water or other working fluid down wells to hot solid rock (much below 1000 C), and then back up to the surface. There's no liquid state magma involved, and it's nowhere near as hot as a volcano itself. In the last big Kīlauea eruption, the geothermal plant had to shut down because things were too active.
How about we bury the waste in a way that doesn't sink, then use the heat in the same way as geothermal?

You could even not bother building the reactor first, and just build big RTGs...

Posted: **Fri Oct 22, 2021 2:55 pm**

dyqik wrote: Fri Oct 22, 2021 2:49 pm
monkey wrote: Fri Oct 22, 2021 1:59 pm How about we bury the waste in a way that doesn't sink, then use the heat in the same way as geothermal?
You could even not bother building the reactor first, and just build big RTGs...

We need the reactors to make the waste to power the RTGs. LIke we needed the reactors to make stuff to go into other, umm, devices.

Posted: **Fri Oct 22, 2021 2:57 pm**

dyqik wrote: Fri Oct 22, 2021 2:49 pm You could even not bother building the reactor first, and just build big RTGs...

RTG? Ah, Radioisotope thermoelectric generator. "The expense of RTGs tends to limit their use to niche applications in rare or special situations."

Posted: **Fri Oct 22, 2021 3:06 pm**

dyqik wrote: Fri Oct 22, 2021 2:49 pm
monkey wrote: Fri Oct 22, 2021 1:59 pm
dyqik wrote: Fri Oct 22, 2021 1:20 pm

Geothermal generally pumps water or other working fluid down wells to hot solid rock (much below 1000 C), and then back up to the surface. There's no liquid state magma involved, and it's nowhere near as hot as a volcano itself. In the last big Kīlauea eruption, the geothermal plant had to shut down because things were too active.
How about we bury the waste in a way that doesn't sink, then use the heat in the same way as geothermal?
You could even not bother building the reactor first, and just build big RTGs...

I suspect there's problems if you try and make one too big.

And we have already have the reactors and their waste, which is just sitting around in swimming pools.

Posted: **Fri Oct 22, 2021 3:13 pm**

monkey wrote: Fri Oct 22, 2021 3:06 pm
dyqik wrote: Fri Oct 22, 2021 2:49 pm
monkey wrote: Fri Oct 22, 2021 1:59 pm

How about we bury the waste in a way that doesn't sink, then use the heat in the same way as geothermal?
You could even not bother building the reactor first, and just build big RTGs...
I suspect there's problems if you try and make one too big.

And we have already have the reactors and their waste, which is just sitting around in swimming pools.

Except at Dounreay, where it's sitting around sunning itself on the beach.

Posted: **Fri Oct 22, 2021 10:25 pm**

After reading David Brin's, Uplift stories* I quite liked the idea of dumping nuclear waste in a subduction zone

*A mistake to start because the first was interesting enough to want to find out more, but there was an increasingly obvious ID agenda, just as Niven and Pournelle have a bit of a global warming denial agenda.

Posted: **Sat Oct 23, 2021 6:34 am**

Off topic. Didn’t know Niven and Pournelle went all anti-science WRT carbon emissions, but can’t say I’m surprised.

Scrutable

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