Disposition of Spent Fuel - Separation option

[Jon Richfield]

Cost. Separating transuranics from fission products requires further processing steps.

Each additional step costs a lot when you work with very, very radioactive materials: it must be done in airtight building, all gaseous emissions and liquid effluents require elaborate filtering, all vessels and piping need to be very durable (since repairs are extremely costly, if practical at all), and all of this stuff requires heavy shielding.

But nikkkom, that makes no sense.

1: Vitrification is not cheap; I doubt that even superficially it is significantly cheaper than reprocessing; you know perfectly well that one does not simply dunk spent fuel rods in molten glass and bobsyouruncle. You first have to get the relevant materials out of the problem material, and convert it to workable form, you then have to work out into what kind of glass (LOTS of glass, please note, it is not just one part Pu, one part glass, one eye of newt and one tongue of dog!) and how to incorporate it as a homogeneous mass. That will COST! Certainly it does not cost as much as isotopic separation, but that is a separate concern; we don't have to separate isotopes until we need to harvest isotopes for purposes that will pay for the process.
2: That process itself produces waste, generally chemically dangerous and generally unacceptably radioactive as well, and not easy to vitrify. More cost!
3: Lots of very smart people have been busting guts (or cerebral vascular systems) to produce ceramic matrices that can be relied on not to dissolve or leak under various underground conditions, and considerable credibility gaps have grown concerning some at first promising-looking materials. Cracks, crystallisation, solution, you name it. So we have a nice new one that won't leak? This year? This century? This millennium? So much nicer than storage in re-usable form against the time that we could have reprocessed the cooled, unmodified fuel assemblies after the demand had grown and the techniques improved? Do tell...
4: Storage of minute volumes of UN-reprocessed high-activity waste, literally cubic metres rather than thousands of cubic metres, in a sealed chamber, accessible for extraction on demand would be a fraction of the cost of such treatment, and it might be expected to be undertaken within decades rather than centuries, after a few cycles of which it would have paid its way and and also would be much safer than the vitrified time bombs that could be expected to remain useless and unacceptably active after many millennia.
In sum, I regard the cost of a rational storage and process-on-demand as far more economical, and probably far safer than vitrification.

 

[nikkkom]

But nikkkom, that makes no sense.

1: Vitrification is not cheap; I doubt that even superficially it is significantly cheaper than reprocessing; you know perfectly well that one does not simply dunk spent fuel rods in molten glass and bobsyouruncle. You first have to get the relevant materials out of the problem material, and convert it to workable form, you then have to work out into what kind of glass (LOTS of glass, please note, it is not just one part Pu, one part glass, one eye of newt and one tongue of dog!) and how to incorporate it as a homogeneous mass. That will COST! Certainly it does not cost as much as isotopic separation, but that is a separate concern; we don't have to separate isotopes until we need to harvest isotopes for purposes that will pay for the process.

I do not understand your point. You seem to imply that with actinide removal, some steps of current process can be removed. That is not true.

IIUC current "state of the art" reprocessing goes as follows:

- fuel pellets are dissolved (say, in nitric acid)
- uranium and Pu are extracted using some organic solvents tailored specifically for these elements. This removes a large fraction of the solution, since spent fuel still has ~95% uranium.
- the remaining solution is calcined (dried into powder)
- the powder is melted with glass (something like 30-50% of power, the rest is glass) and poured into stainless steel vessels

If you want to remove actinides, you can't avoid any of the above steps. You also likely can't just modify a step. You need to *add* another step (probably it will have to be inserted after U/Pu removal). That inevitably increases cost.

3: Lots of very smart people have been busting guts (or cerebral vascular systems) to produce ceramic matrices that can be relied on not to dissolve or leak under various underground conditions, and considerable credibility gaps have grown concerning some at first promising-looking materials. Cracks, crystallisation, solution, you name it. So we have a nice new one that won't leak? This year? This century? This millennium? So much nicer than storage in re-usable form against the time that we could have reprocessed the cooled, unmodified fuel assemblies after the demand had grown and the techniques improved? Do tell...
4: Storage of minute volumes of UN-reprocessed high-activity waste, literally cubic metres rather than thousands of cubic metres, in a sealed chamber, accessible for extraction on demand would be a fraction of the cost of such treatment, and it might be expected to be undertaken within decades rather than centuries, after a few cycles of which it would have paid its way and and also would be much safer than the vitrified time bombs that could be expected to remain useless and unacceptably active after many millennia.
In sum, I regard the cost of a rational storage and process-on-demand as far more economical, and probably far safer than vitrification.

In case you are arguing for not doing reprocessing at all, yes, it is an option which seem to be followed by US right now. If it means just storing fuel, it is okay. It even has economic benefits, since less radioactive fuel is probably somewhat cheaper to reprocess.

However, it feels like just postponing a decision to either reprocess or bury it as-is. Eventually you will have to choose what to do.

 

[Jon Richfield]

I do not understand your point. You seem to imply that with actinide removal, some steps of current process can be removed. That is not true.

IIUC current "state of the art" reprocessing goes as follows:

- fuel pellets are dissolved (say, in nitric acid)
- uranium and Pu are extracted using some organic solvents tailored specifically for these elements. This removes a large fraction of the solution, since spent fuel still has ~95% uranium.
- the remaining solution is calcined (dried into powder)
- the powder is melted with glass (something like 30-50% of power, the rest is glass) and poured into stainless steel vessels

If you want to remove actinides, you can't avoid any of the above steps. You also likely can't just modify a step. You need to *add* another step (probably it will have to be inserted after U/Pu removal). That inevitably increases cost.
In case you are arguing for not doing reprocessing at all, yes, it is an option which seem to be followed by US right now. If it means just storing fuel, it is okay. It even has economic benefits, since less radioactive fuel is probably somewhat cheaper to reprocess.

However, it feels like just postponing a decision to either reprocess or bury it as-is. Eventually you will have to choose what to do.

Firstly nikkkom, removal of actinides immediately changes the game. It counts as reprocessing, which is anathema to the anti-nuke brigade. What are you going to DO with those actinides (actinoids, whatever)? Build bombs right? No? A likely story! But if not then what? Fuel MORE power stations? HAH! Just as we thought, breeding more deadly fuels that will poison us all. None of your nonsense, we want all that deadly stuff vitrified and stored safely for at least a few million years, and NIMBY at that!

Well, then we would need to vitrify the actinoids as well, no? A very different kettle of fission.

My proposal is:
* Usual procedure after removal from the core until things cool off till heat is no longer a significant factor. Use whatever you find it profitable to use (meaning pretty well nothing at present AFAIK.)
* Store the cool material sanitarily under conditions such as we have agreed on as being hard to hijack, and with careful cataloging of history and status. This storage to be continued ad Kalendas Graecas or otherwise convenient occasion. There is no point to processing them before such time, and the longer they are left, the smaller the content of troublesome volatile components such as iodine or krypton. (Unless of course, you WANT iodine or krypton!)
* When the occasion does arise, select the most suitable items for the current requirement and process them more or less as you have described. Very likely the desired materials will be actinoids, but that doesn't much matter. The consumers will determine what they want and when.
* Having disposed profitably of the desired products such as Am-free Pu, you extract as much as practical of the non-radioactive residue for safe disposal, and return the rest to clean, dry, sealed, (re)cataloged storage.
* Should it be determined that certain residues for some reason never could be regarded as worth retaining, even as thermal fuel for disposable space modules, and that it remains sufficiently dangerous to be worth genuinely destroying, expose them to a suitable neutron flux to render them inactive or so radioactive that they soon will decay to inactivity.

Such procedures wouldn't waste anything much nor risk anything much, nor cost much over and above the storage and processing costs that clients would be happy to pay anyway.

No?

 

[nikkkom]

Should it be determined that certain residues for some reason never could be regarded as worth retaining, even as thermal fuel for disposable space modules, and that it remains sufficiently dangerous to be worth genuinely destroying, expose them to a suitable neutron flux to render them inactive or so radioactive that they soon will decay to inactivity.

I don't think you can economically destroy fission products this way. While neutrons would transmute, say, Cs-137 to Cs-138 which quickly decays to stable Ba-138, it will also transmute stable Cs-133 to radioactive Cs-134.

 

[Jon Richfield]

I don't think you can economically destroy fission products this way. While neutrons would transmute, say, Cs-137 to Cs-138 which quickly decays to stable Ba-138, it will also transmute stable Cs-133 to radioactive Cs-134.

Your remark might be correct, but I suspect it is over pessimistic.

* The approach might prove unnecessary if uses were found for enough isotopes
* Burning also might prove unnecessary because the final volume of problem isotopes would be too small to make permanent storage unattractive.
* If we did opt for isotope burning, one would have to consider which isotopes are of practical interest. Look at Si-32. Nasty, very nasty! Half-life of 700Y B-emission; intolerable! Active enough to be dangerous, but too stable to make it acceptable to wait for it to decay. And it might be difficult to burn anyway with such a neutron excess. And yet, I don't know how much we produce or whether we would want use it for anything, but it is easy to immobilise chemically if we don't want it. It is not as mobile as say I-131, or as readily absorbed or retained, so it is not under realistic circumstances a major concern. Each element and each isotope can be considered in its own contexts of its halflife, its biological effects, its mobility in the environment, its projected inventories, and its burnability.
*Also consider your examples of Cs isotopes. We need not take them too seriously because the example is academic, but I think it is illustrative. One might not bother to "burn" them at all. Cs-137 has a half-life about 30 years; only about .1% would be active after 300 years and it is not a very powerful source anyway. One MIGHT simply bury stocks where they would be safe for 1000 years. (About 33 half lives, right? About 1 eight-millionth residue?) Cs-134 shouldn't be too much of a problem even if you did get a lot of it (not all that likely, yes?) because its half life would reduce 99.9% of the inventory to stable Ba in less than 30 years.
* In fact that example should remind one that the point of burning troublesome isotopes works two ways: produce less-active or inactive isotopes, or produce MORE active isotopes that will decay to stability faster, as you instanced in the Cs-138 example, even if there were troublesomely large amounts of Cs-133 in the input.
* Note too the tendency for decay by neutron capture; the trend is to produce isotopes that are more neutron-rich and less neutron-greedy. One naturally would need to tune treatments for best results, but that trend is helpful.
* A lot of the treatment could be simply by storage of the concentrated wastes in specially neutron-rich regions on the periphery of active fission plants. Note that "burning" non-concentrated wastes would make no sense anyway. We probably would be interested in burning only trace quantities if any at all.

I am not arguing that isotope burning would inevitably be necessary; in fact it goes against the grain for my part, but if it were to prove necessary, I suspect it would be practical.

 

[mheslep]

If the total fission product waste stream mass from a reactor is 3%, and the radiotoxcity decays below that uranium ore in ~300-400 years, it seams to mean burial is a reasonable option. It seems to me therefore that the focus of waste discussions should be on a solution for the actinides, on fast spectrum reactors or thorium fuel cycles that leave no actinides, while at the same time greatly expand the fuel supply.

 

[Jon Richfield]

If the total fission product waste stream mass from a reactor is 3%, and the radiotoxcity decays below that uranium ore in ~300-400 years, it seams to mean burial is a reasonable option. It seems to me therefore that the focus of waste discussions should be on a solution for the actinides, on fast spectrum reactors or thorium fuel cycles that leave no actinides, while at the same time greatly expand the fuel supply.

Now, THAT sounds like something else. I like it. My only reservation is that I distrust burial. I prefer storage. The storage COULD take the form of burial I guess, but I would like to be sure that we know what is where at all times.

 

[nikkkom]

Each element and each isotope can be considered in its own contexts of its halflife, its biological effects, its mobility in the environment, its projected inventories, and its burnability.

It's possible to separate waste into individual elements, but this costs a lot.
Theoretically it's possible to separate isotopes too, but this costs astronomical sums if done on many kilogram scales.

IOW: both are non-economical.

 

[nikkkom]

Now, THAT sounds like something else. I like it. My only reservation is that I distrust burial. I prefer storage. The storage COULD take the form of burial I guess, but I would like to be sure that we know what is where at all times.

There are cases when it's not economical. The final product of vitrification is completely useless. Storing it will just make us spend money on it for millennia. Why not bury it in boreholes in a subduction zone? What's wrong with that?

 

[Jon Richfield]

It's possible to separate waste into individual elements, but this costs a lot.
Theoretically it's possible to separate isotopes too, but this costs astronomical sums if done on many kilogram scales.

IOW: both are non-economical.

You will notice that I avoided discussion of isotope separation because I assumed that it would be too expensive.

In contrast however, separation of elements is not generally dramatically expensive, though of course it is not something one does just for laughs, particularly when radioactivity is a factor. (OH, and BTW, when I speak of "elements" I am not speaking of pure elements, but convenient compounds for handling storage or disposal, such as oxides, fluorides, carbonates, magnesium salts etc).
As for its being uneconomic, it might be if the alternative is to store it a few centuries, but if you get the material in a residue from which you want particular elements or isotopes, or if you want to reduce bulk to be stored, it could very cheerfully be economic. I reckon that a blanket dismissal is inappropriate.

 

[Jon Richfield]

There are cases when it's not economical. The final product of vitrification is completely useless. Storing it will just make us spend money on it for millennia. Why not bury it in boreholes in a subduction zone? What's wrong with that?

I agree about vitrification products generally being useless and the same for ceramic compaction, and see no point to either. Burial in subduction could work just as well in corrosion resistant tough metal capsules, because once it is on the down elevator, who cares about a few leaks during the next few million years, by which time who cares anyway; that is a LONG way down the half life ladder.

But what gives you the idea that burial in a subduction zone is simple, safe, and cheap, compared to storage in a near-surface, secure underground chamber? How deep do you want to go, and how much do you want to bury? I trust you don't think that a few hundred feet into the bedrock would be sufficient?

 

[nikkkom]

You will notice that I avoided discussion of isotope separation because I assumed that it would be too expensive.

In contrast however, separation of elements is not generally dramatically expensive, though of course it is not something one does just for laughs, particularly when radioactivity is a factor.

Wrong. When radioactivity of the source material is in MILLIONS of rems per hour, as is the case here, there is a BIG difference. Reprocessing as currently done is essentially removal of two elements: U and Pu. It is a fact that it is expensive.

 

[nikkkom]

I agree about vitrification products generally being useless and the same for ceramic compaction, and see no point to either. Burial in subduction could work just as well in corrosion resistant tough metal capsules, because once it is on the down elevator, who cares about a few leaks during the next few million years, by which time who cares anyway; that is a LONG way down the half life ladder.

Wrong. Metal capsules are neither sufficiently tough nor sufficiently corrosion resistant over millennia in hot, high pressure environments.

You need *waste itself* to be in a chemically inert, insoluble form, so that hot water won't leach fission products out of it.

Do you really think people who designed reprocessing are idiots?

But what gives you the idea that burial in a subduction zone is simple, safe, and cheap, compared to storage in a near-surface, secure underground chamber? How deep do you want to go, and how much do you want to bury? I trust you don't think that a few hundred feet into the bedrock would be sufficient?

3-4 kilometers would do. Oil and gas exploration industry routinely drills much deeper than this.

As to difficulty of burial, here's the end product of La Hague vitrification plant: a cylindrical canister of ~40 cm diameter:

I don't see why lowering these down a borehole would be a problem.

 

[Jon Richfield]

In the context of "it is uneconomic" as someone asserted, there is a difference between "expensive" and "dramatically expensive". The expression that I used was the latter, right?

It also depends on what is being done, and what for.

To do ANYTHING at that level of activity is expensive, which is one good reason for not reprocessing fuel until you really need to (by which time in dealing with commercial enterprises, you should be years down the line). It does not follow that it would be unprofitable, which is a totally different matter. Right?

But even if you are dealing with barely-cool fuel to extract the U and Pu, which obviously was worth the expense, or you wouldn't be doing it in the first place, then continuing to extract residual materials apart from those two elements is not a monumental overhead if the other materials in question are something you badly want. Much as it was worth extracting the U and Pu originally. Opportunism they call it.

Note that vitrification of those items would have been expensive too, and you would have got nothing out of it; not now, not later. This way you would have got, say Tc and Pm isotopes, saving the costs of mining them, which would have been REALLY dramatically expensive.

Right?

 

[mheslep]

Two different waste streams are in play in this discussion: i) the tradition nuclear spent fuel with actinides and mostly U238 by mass, and ii) fission products only, i.e. the waste from a fast or thorium fueled reactor, or separated out after reprocessing from traditional spent fuel. Geologic disposal is arguable for the first, but not the latter.

 

[Jon Richfield]

Wrong. Metal capsules are neither sufficiently tough nor sufficiently corrosion resistant over millennia in hot, high pressure environments.

Firstly nikkkom, how did you arrive at that no doubt well-founded conclusion?
How hot?
Since when does say a few hundred K (which is a heck of a lot more than anyone would be drilling in) imply that mild steel couldn't stand it? What would the content of water and acid be in that environment?
What pressures are you discussing that we should be keeping out? We are not trying to protect fragile items from collapse, but essentially solid material that would barely deform in the absence of shear forces after it had finished compacting, even if it were made of talc. And what source of shear forces would a say, 150cm-long, 50cm-thick capsule (edited to come a bit closer to the canisters that you posted) encounter that would affect it at all below about 1700K? Plastic rock doesn't swirl like rapids and at those temperatures all the common rocks are pretty well molten. Our dime-store mild-steel pipe would represent a nice rigid rock in the current.
You surely didn't think that the drill would go down to to magma did you, even if the capsules landed up in magma an aeon later in its process of subduction? And at that time who would care? Even if they were down the hole along with the capsule?
And if the course of subduction did bring the capsule into rock at say 1500K (which is already pretty hot for magma, though not as hot as some), and the capsule did start to deform, then once more, who would care; it would already have traveled several km downwards, which would take millennia or a good deal longer, and though it would deform, the iron still would not have melted.
I think a bit of calculation plus some rational specification of the plausible conditions would be in order before asking me about whether the hypothetical engineers are fools or not. Have you actually discussed any of these points with them before attributing opinions?
Just asking...

 

[Jon Richfield]

Two different waste streams are in play in this discussion: i) the tradition nuclear spent fuel with actinides and mostly U238 by mass, and ii) fission products only, i.e. the waste from a fast or thorium fueled reactor, or separated out after reprocessing from traditional spent fuel. Geologic disposal is arguable for the first, but not the latter.

Sounds good to me. I for one wasn't discriminating between those two, because my argument is independent of that point. I was expressing my suspicion of vitrification and subduction (or similar permanent disposal of high-intensity waste) in general.

Conversely (and, I admit, irrelevantly) I remark that the anti-nuke brigade would not be happy with less than subducting the whole caboodle, including the concrete of the buildings, and I bet I could find some parties who would be happy to fund an injunction against nuclear pollution of subducting magma as well! (Is anyone betting?) :)

 

[Jon Richfield]

You need *waste itself* to be in a chemically inert, insoluble form, so that hot water won't leach fission products out of it.

No you don't. All you need is a container that won't let water in at shallow levels so cool (below about 400K) that liquid water could exist around it. By the time that becomes relevant your capsules will be another km or two deeper. I live near where living humans work voluntarily in mines deeper than 3 km with no more than some air conditioning, and not a vein of boiling water in sight.
Not that *I* would volunteer there, you understand, but at least hundreds of thousands do, year in and year out since before I was born.
By the time you get deep enough to compromise the canister (say another few km) there would not be much liquid water anyway and we would be out of sight of anything resembling ground water, but if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide.
And why chemically inert? If it comes to that, HOW chemically inert? Fuming nitric acid or explosives would be poor prospects for such treatment, but when was the last time anyone suggested disposing of such materials in such a manner?
But what about say, reactive materials such as metals and common salts such as sulphates or carbonates? How do you see them leaching out? If they did, how far from the parent capsule would you expect them to leach in densely compacted rock? A metre? How?
And insoluble? In what? Molten rock?Even your vitrification material would dissolve in really deep magma, right?
I don't think you or your sources have worked this out very carefully. Sorry!

 

[Jon Richfield]

Do you really think people who designed reprocessing are idiots?

Sorry, you lost me there. Who suggested that people who designed reprocessing are idiots?
I do accept that deep burial of vitrified high activity waste is an idiotic idea, but that is a totally different matter.

3-4 kilometers would do. Oil and gas exploration industry routinely drills much deeper than this.

That is a comforting assurance; where did you get the figure, and who ratified it? I assume that you have seen diagrams of what happens at the interface between the subducting plate and the overlying plate? Perhaps there are regions where such depths would suffice, but what sort of brinkmanship would be acceptable in playing chicken to see whether the canisters get truly subducted, or scraped off and exposed near the surface?

However, the point is trivial in comparison with the question of what it costs to drill so deep into hard rock. Is that your idea of a solution to the disposal problem, to rival the cost of near-surface storage? Even for a few centuries?
Suppose our store had a few thousand square metres of storage space; how much drilling (3-4 km deep forsooth!) would it take to dispose of the potential capacity of a store on such a scale?
"Out of sight is out of mind" is a tempting principle, but if it turned out that something had gone horribly wrong, such as say, the process of subduction not behaving as expected, where would you rather have the waste? Up here, or no longer quite so "down there"?

As to difficulty of burial, here's the end product of La Hague vitrification plant: a cylindrical canister of ~40 cm diameter: ... I don't see why lowering these down a borehole would be a problem.

I find that statement confusing. I thought that I had explained that the main problem is the cost of drilling, plus loss of control thereafter; a drilling engineer would no doubt be able to explain a few in addition. However, I DO hope that you are not under any illusion that it is just a matter of drilling and dropping! Just the delivery to the bottom of the hole, plus sealing them in place would be a fairly fraught procedure, compared to storage as I have described it.
What exactly had YOU thought?

 

[nikkkom]

Firstly nikkkom, how did you arrive at that no doubt well-founded conclusion?
How hot?
Since when does say a few hundred K (which is a heck of a lot more than anyone would be drilling in) imply that mild steel couldn't stand it? What would the content of water and acid be in that environment?

The acidity of the underground water in the future can't be easily predicted. You should assume the worst (that it, that it will be acidic). Hot acidic water dissolves steel on a timescale of a decade. Look at photos of any abandoned mine.

 

[nikkkom]

if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide.

Organics are not stable in high radiation fields.

How do you see them leaching out? If they did, how far from the parent capsule would you expect them to leach in densely compacted rock? A metre? How?
And insoluble? In what? Molten rock?Even your vitrification material would dissolve in really deep magma, right?
I don't think you or your sources have worked this out very carefully. Sorry!

Water.

 

[Jon Richfield]

The acidity of the underground water in the future can't be easily predicted. You should assume the worst (that it, that it will be acidic). Hot acidic water dissolves steel on a timescale of a decade. Look at photos of any abandoned mine.

Assuming the worst doesn't mean being unrealistic. If I am allowed to assume anything I like, I can assume aliens sneaking in by night to remove capsules from underground.
And not all corrosion in abandoned (or active ftm) is caused by acids by any means. Salts, microbes, oxidation cycles, electrolytic contacts, alkalis, they all can do nasty things even to acid-passivated materials; why pick on acids in particular?
You say that "Organics are not stable in high radiation fields.", but that is a hopeless generalisation. If your radiation is sufficiently intense, nothing is stable, including solid metal and nuclei that spall. But if we keep our assumptions realistic, then to prepare radiation-resistant polymers or chars or corrosion resistant ceramics or metals is hardly a novel requirement.
For example, I noticed in passing that the capsules that you displayed as being easy to drop down the hole had been clad in metal by some wild optimist.
Was HE an idiot, do you suggest? Or did he just know metallurgy well enough to make realistic assumptions?
If I bury capsules on realistic assumptions, I shouldn't do so in places where I could not drill past any ground water, and I should do so where, if any water did get in, there would not be much tendency for any flow. And I should seal the dry hole with clayey materials for a few hundred metres at least.
Then if alien gremlins did rupture my impenetrable capsules on a grand scale, I would tragically yawn "Ho hum!"
After all, why did I bury the stuff in a subduction zone in the first place?
And why deeply enough to follow the flow of subduction to the Earth's mantle?
And why did I cover it in a medium that retards seepage?
And adsorbs practically any ion you could mention?
What would make any leaks escape further than a fraction of a percent of the way to the nearest roots or water or air?

And what did any of that have to do with how much cheaper it was to bury stuff than to store or reprocess it?
You still have given no grounds for any opinion that burial would be safer or cheaper than storage, let alone more effective or more rewarding if it turned out that there was a need for any of the material at some future time.
You WILL be getting to that sometime I hope?

 

[nikkkom]

Assuming the worst doesn't mean being unrealistic. If I am allowed to assume anything I like, I can assume aliens sneaking in by night to remove capsules from underground.
And not all corrosion in abandoned (or active ftm) is caused by acids by any means. Salts, microbes, oxidation cycles, electrolytic contacts, alkalis, they all can do nasty things even to acid-passivated materials; why pick on acids in particular?

I'm not picking on acids in particular. All realistic underground conditions need to be evaluated, acid as well as basic.

You say that "Organics are not stable in high radiation fields.", but that is a hopeless generalisation. If your radiation is sufficiently intense, nothing is stable, including solid metal and nuclei that spall.

Organic compounds are less stable to radiation because they are complex molecules whose properties strongly depend on molecules retaining their structure. Metals, inorganic crystalline and glassy materials are more stable to radiation damage.

If I bury capsules on realistic assumptions, I shouldn't do so in places where I could not drill past any ground water

There are hardly any place on Earth where there is no underground water. Watch the videos. You seem to be typing so fast you did not bother watching them.



At and after 9:00 in this video steel borehole casing is seen to be rusted through.

 

[Jon Richfield]

I'm not picking on acids in particular. All realistic underground conditions need to be evaluated, acid as well as basic.

Yes nikkkom. That is what I was explaining to you. I gave you some examples, remember?

Organic compounds are less stable to radiation because they are complex molecules whose properties strongly depend on molecules retaining their structure. Metals, inorganic crystalline and glassy materials are more stable to radiation damage.

Thanks nikkkom but you needn't go out of your way to explain Org chem 101. In response to my remark on your generalisation about organic chemicals' sensitivity to radiation you now have added aggravated handwaving. Granted that organic chemicals such as methane are highly complex and that rearranging their bonds can change their nature (in contrast to inorganic compounds, would you say?) it does not follow that every change is undesirable or even relevant. You could make a similar claim about heating or cooling organic (or inorganic) substances. Materials engineering is all about such considerations. The question is not whether radiation will break this bond, couple those molecules, or transmute that nucleus, but how it will affect the nature of the substance, desirably or otherwise, and how to exploit or mitigate the results. This applies to any sort of material from polymeric packing to metallic core cladding, right? Or do you have more news for me?
I would say that is pretty basic, wouldn't you? What makes you think that it means that if it is possible for waste to transform cladding, then cladding cannot be trusted?
All of which is so emphatic that it might be difficult to bear in mind that the original point was that adequate encapsulation for disposal in a subduction zone could be a chunk of mild steel (or even soft iron ftm) piping, but that in case you happened to be feeling itchy, you might wish to add a bit of lining or coating. Galvanizing might do I suppose, if it didn't add too much to the costs...

There are hardly any place on Earth where there is no underground water. Watch the videos.

...

At and after 9:00 in this video steel borehole casing is seen to be rusted through.

I particularly liked the main one about the various things one sees down boreholes; really interestingly informative. If I were a well manager, I would happily consider contracting a company with such articulately friendly and persuasively interpretive staff. However, there was very little material with any bearing on our topic. You get water in shallow wells of a few thousand feet? The water might be aggressive? So what?
Far more interesting IMO was the crumpled up jacketing, that in principle might count as a dusty answer to your assumption that it necessarily is simple to dump expensive (and expensively prepared) shiny metal canisters down a well ad lib.
The footage and discussion did not for a moment suggest that if you could get your canister down to hottish subducting rock (say 5-10 km) and cover it with a bit of clay, that you should care a dam whether the containment lasts one year or a million years. The migration of radioactive species would be derisory.
Frankly I reckon that if you got it down to cool, wet, acid rock at 3 km and that you did manage to do so in reliably subducting rock, you still could cock a snook at any disruption after you had clayed it. Realistically, how far could it migrate away from the deposit?

Bottom line:
Sure you could safely subduct waste without vitrification and with only marginal precautions and common sense and technical competence, but apart from being unnecessary and wasteful, it would be hellishly expensive. Uneconomic or economic? That would depend on whether people were willing to pay for it. *I* wouldn't, because for a start I like things to be under control, like in safe storage at the surface, but anything for a quiet life...

 

[nikkkom]

Granted that organic chemicals such as methane are highly complex and that rearranging their bonds can change their nature (in contrast to inorganic compounds, would you say?) it does not follow that every change is undesirable or even relevant. You could make a similar claim about heating or cooling organic (or inorganic) substances. Materials engineering is all about such considerations. The question is not whether radiation will break this bond, couple those molecules, or transmute that nucleus, but how it will affect the nature of the substance, desirably or otherwise, and how to exploit or mitigate the results. This applies to any sort of material from polymeric packing to metallic core cladding, right?

Typing loads of rubbish won't hide the fact that your suggestion of using organics to increase stability of nuclear waste won't work.

It is not my opinion, it is a _fact_ that organic materials are not used for any sort of insulation or seals in nuclear waste storage, spent fuel storage, or in nuclear reactors. Metals, ceramics and glass are used instead.

There was an attempt of using an organic coolant in one experimental reactor design. After a day of operation, it turned to black gunk of unknown composition.

 

[Jon Richfield]

Typing loads of rubbish won't hide the fact that your suggestion of using organics to increase stability of nuclear waste won't work.

I admit to disappointment that you descended to abuse of substantial material that you found unanswerable, even when the topics had been in response to points that you had raised, not I, and that I had responded to with such patience as I could muster. I invite your attention to the fact that I don't and didn't suggest anything like "using organics to increase stability of nuclear waste". It isn't even clear that anything, organic or otherwise, could affect its stability, but by all means feel welcome to instance some mechanism by which orbital chemistry might be expected to affect decay rates.

Please note, in preparing your response, that your entire (inaccurate) assertion that organic molecules are essentially universally degraded too rapidly to be of use in the presence of radiation, is a red herring that you introduced irrelevantly in response to my argument that neither vitrification nor impregnable encapsulation was necessary in preparing waste for deep burial, especially in subduction zones. I said that mild steel (or even soft iron) should be adequate for that purpose, and thoughtlessly added as an aside that if you really were worried about corrosion, suitable coatings and linings could alleviate or even banish the problem. You now seem to assure us that the inevitable product would be "black gunk of unknown composition" or some similar product, ignoring the fact that such a black gunk might be a perfectly adequate corrosion barrier in the circumstances, even though I personally don't think it greatly matters at all. Nor does it follow that because an unnamed organic coolant produced such a gunk, every organic anti-corrosion agent must do so. Nor does it even follow, as I seem to remember pointing out, that the anti-corrosion coating must be organic.

NOW where's the rubbish?

It is not my opinion, it is a _fact_ that organic materials are not used for any sort of insulation or seals in nuclear waste storage, spent fuel storage, or in nuclear reactors. Metals, ceramics and glass are used instead.

And?
Who mentioned any of those in this context of waste disposal, as you introduced it?

Well now, I don't know how to put things yet again more clearly, but perhaps you would find yourself wading through less rubbish if you stuck to the point, which I have repeatedly stated and illustrated. Try this version once more:

Bottom line:
Sure you could safely subduct waste without vitrification and with only marginal precautions and common sense and technical competence, but apart from being unnecessary and wasteful, it would be hellishly expensive. Uneconomic or economic? That would depend on whether people were willing to pay for it. *I* wouldn't, because for a start I like things to be under control, like in safe storage at the surface, but anything for a quiet life...

 

[nikkkom]

I invite your attention to the fact that I don't and didn't suggest anything like "using organics to increase stability of nuclear waste".

Yes, you did. "if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide." Your words.

 

[Jon Richfield]

Yes, you did. "if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide." Your words.

Are you trying to be funny?
What on Earth does "if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide" have to do with the stability of your waste?
Are we speaking the same language? Prevention of the canister dissolving has NOTHING to do with the physical (or even the chemical) stability or activity of the waste.
And what makes you think that either of those types of lining would fail to provide reasonable acid protection for long enough for you to charge the canister and put it down the hole? Have you ever tried to dissolve a hole in a thickish iron pipe in a strong acid at a reasonable concentration for ground water? It doesn't just happen like lighting flash powder you know? And even degraded polyimide free from cracks would exclude acid indefinitely.

But are you so bereft of points in favour of your argument that you absolutely must flinch from the real issues all the time?
Costs?
Waste?
Risk?
At the risk of boring me, I repeat:

Bottom line:

Sure you could safely subduct waste without vitrification and with only marginal precautions and common sense and technical competence, but apart from being unnecessary and wasteful, it would be hellishly expensive... blahblah.

That is the point I have been making. Repeatedly. It contradicts every assertion of the advantages of burial or subduction in comparison to storage, and you have done nothing but harangue me on how useless polymer coatings would be underground in the presence of radiation.

Do you really have nothing better?

 

[nikkkom]

Are you trying to be funny?
What on Earth does "if you were nervous of your canister dissolving, you could line it or lacquer it with cheap high temperature nylon or polyimide" have to do with the stability of your waste?

You suggested that such lining can be used to prevent waste from being leached out by water.
This won't work because the lining will degrade too quickly.
The waste itself has to be chemically insoluble.

Are we speaking the same language? Prevention of the canister dissolving has NOTHING to do with the physical (or even the chemical) stability or activity of the waste.
And what makes you think that either of those types of lining would fail to provide reasonable acid protection for long enough for you to charge the canister and put it down the hole?

No, we are not speaking the same language. In fact, you seem to intentionally distort my position in your last four posts.

Waste needs to be stable against dissolution by groundwater not only before and during burial, it must be insoluble AFTER burial too, and stay insoluble for at least a few thousand years.

 

[Jon Richfield]

You suggested that such lining can be used to prevent waste from being leached out by water.
This won't work because the lining will degrade too quickly.
The waste itself has to be chemically insoluble.

I didn't suggest it. I stated specifically that it could if you chose the right materials. These would include various organic materials, but if you were obsessive about it, the options include a wide range of alternatives. However, as I described more than once, even if the waste were completely liquid but were established sufficiently deeply it wouldn't matter a dam because its mobility would be negligible. Which is fortunate, because by the time it got subducted to deep magma, (which you described as easy to achieve, remember) it would be released anyway, though you seem to think that it would be covered by water, no matter how deeply it sank.

You give no basis for your pious conviction that "This won't work because the lining will degrade too quickly." When did you last check to see how fast it would degrade, when you don't even know what the lining would be? Why should anyone treat your conviction seriously? Because you personally observed a cooling agent turn into black gunk overnight?

Must try harder.

"Chemically insoluble" is a technical illiterism. I hope you don't think you know what it means.

No, we are not speaking the same language. In fact, you seem to intentionally distort my position in your last four posts..

*I* did nothing of the type. Intentionally or not you made your position so untenable that in the last several messages you weren't even mentioning the original point at all, in spite of my weary repetition.

Waste needs to be stable against dissolution by groundwater not only before and during burial, it must be insoluble AFTER burial too, and stay insoluble for at least a few thousand years.

Nonsense. Depending on its content it might take millions of years, during which time all that is necessary is that it stays down, solid or not, and if it is indeed in a subduction layer, that should be no problem.
Don't you even understand the concept of underground mobility? And the question of the relevance of water where rock is approaching plasticity?

And if you don't, why do you keep fleeing the actual question, which was and still is why anyone in his right mind would want to drill down dangerously and expensively for multiple km to bury possibly valuable material that could safely and economically be stored at or near ground level?

I bet that you chicken out of that one again, being at the fifth or thereabout time of asking, and without your being able to mount a single objection other than errr... what?

 

[nikkkom]

However, as I described more than once, even if the waste were completely liquid but were established sufficiently deeply it wouldn't matter a dam because its mobility would be negligible.

No matter how many times you say it, it still remains completely false. In any achievable burial depth (even ~10km), water-solible forms of waste can reach surface on a timescale of one century.

 

[nikkkom]

why anyone in his right mind would want to drill down dangerously and expensively

Wrong. Drilling boreholes is neither particularly dangerous nor particularly expensive. US drills about 35 thousand gas wells every year today (fracking).
Where's the danger? I take thousands are dying?
Where are horrible expenses? Natural gas in US become very cheap.

The expertise in deep borehole drilling is already extensive, and becoming more advanced by the day. The old videos in this thread already show wells 4+ km deep being inspected.

The "expensive" part is reprocessing - but we already have it working. Huge expenses in R&D already are paid for!

for multiple km to bury possibly valuable material that could safely and economically be stored at or near ground level?

Because pushing our waste onto our grandchildren is irresponsible. If we produce it, we should dispose of it in a way which does not require our grandchildren to deal with it in perpetuity.

I disagree that waste after reprocessing has any significant value.

 

[Jon Richfield]

Wrong. Drilling boreholes is neither particularly dangerous nor particularly expensive. US drills about 35 thousand gas wells every year today (fracking).
Where's the danger? I take thousands are dying?
Where are horrible expenses? Natural gas in US become very cheap.

Do me a favour!
You are confusing "cheap" with "profitable". This isn't even economics 101; it is primary school common sense. You are confusing costs of established commercial practice with exploratory developmental practice. You are confusing drilling for production, with drilling for disposal. You are confusing every kind of reprocessing with every other, whether actinoid extraction or isotopic separation. Do I have to spell out everything for you as well as keeping your nose on the relevant track?

The reason that gas (for now anyway) is cheap is that you get a lot of fuel for every successful hole. If a hole that costs $10M to drill yields say, $20M profit in gas, it certainly is profitable. It very certainly is not cheap.
If a hole costs $100M dollars to drill a huge amount deeper (because we can't risk irresponsibly "pushing our waste onto our grandchildren" in holes just 10km deep because "any achievable burial depth (even ~10km), water-solible forms of waste can reach surface on a timescale of one century" (a nice line of hooey that!) ) and doesn't yield a cent's worth of gas or anything else of value, that is more than just expensive, it is ridiculous.

Isn't it? Let's hear your direct response to that for a change.

Remember too that although, astonishingly: "The expertise in deep borehole drilling is already extensive, and becoming more advanced" ("by the day" yet! MEGO!) the costs and risks attendant on drilling deeper than more shallowly do not rise linearly; whether they rise polynomially or exponentially (personally I suspect they rise discontinuously though monotonically, but I do not undertake to prove it) but I leave it to your imagination to find means of denying it. You could start by proving why organic materials down there would end up as black gunk, or perhaps by showing why it might be cheaper to dig a 10km hole for waste disposal than a 1km hole for gas.

You fail to establish let alone explain what you are talking about here: "The "expensive" part is reprocessing - but we already have it working. Huge expenses in R&D already are paid for!" Could you please elaborate? I thought you were *objecting* to "reprocessing" whatever you mean by that. A few exchanges back you were berating me for stupidly promoting "expensive" (though deferred) reprocessing. What on Earth changed your mind about that?

Because pushing our waste onto our grandchildren is irresponsible. If we produce it, we should dispose of it in a way which does not require our grandchildren to deal with it in perpetuity.
I disagree that waste after reprocessing has any significant value.

That sounds so virtuous that I barely can bring myself to beg forgiveness for pointing out that the billions of cubic metres of wastes we push onto our grandchildren from mining, processing and consuming combustible fossil fuels (look up what "fossil" means; I am not referring to palaeontology) and not counting the huge waste volumes that we spew into our ever-warmer atmospheric duvet, not only dwarf our heritage of a few cubic metres of highly active wastes, and our few thousand cubic metres of uninteresting nuclear wastes, but also contain more radioactivity calculated as as Becquerels.
So virtuous in fact that I blush to add that where fuel mining and ash dumping have created desert regions, our showcase nuclear disaster region, Chernobyl, has become a thriving sanctuary for wildlife, as have exclusion zones around intact installations like Koeberg and abandoned nuclear plant.

Your agreement or disagreement "that waste after reprocessing has any significant value" is totally irrelevant one way or the other, without demonstration one way or the other. What is undebatable is that once shoved down the oubliette the waste certainly is valueless as well as being a hugely expensive possible hazard if we are to take your own assertions of leaky 10km holes at face value. Conversely, when stored accessibly at a tiny fraction of the cost of burial, it remains for "our grandchildren" to decide on its value, significant or otherwise. Who are you to preempt that evaluation for them?

 

[nikkkom]

I thought you were *objecting* to "reprocessing" whatever you mean by that. A few exchanges back you were berating me for stupidly promoting "expensive" (though deferred) reprocessing.

This entire exchange started when I said that I like very much what French do: reprocessing. (Specifically, the post #517 from Feb 17, 2015). You are distorting my position 180 degrees.
Also, your post contains personal attacks.
I am not interested in trolling wars.

 

[Jon Richfield]

This entire exchange started when I said that I like very much what French do: reprocessing. (Specifically, the post #517 from Feb 17, 2015). You are distorting my position 180 degrees.
Also, your post contains personal attacks.
I am not interested in trolling wars.

What the French are doing, as I understood it, was nearly exactly what I have been proposing in the first place, and I made a remark to that effect at that time (remember?): keep the spent fuel and look after it intelligently until they need it. Then reprocess, reducing the waste in the process and deferring buildup of undesirable transplutonics, leaving small volumes of already mitigated waste that are easier to deal with than burying the lot.
What they are doing with what they now regard as final waste I don't much mind, but I bet that if they want any part of it they don't waste that either. If currently they bury those residues, then I reckon that in that at least they are being uncharacteristically wasteful but one cannot have everything and they very likely will learn better practices in the long run.
Even earlier you remarked that you were no longer in favour of nuclear power at all, so it follows that you are inconsistent in your arguments if suddenly you like the French reprocessing. In this respect I freely admit that you have proved uncharacteristically consistent, so don't go saying that I don't give credit where due. _Your_ accusing _me_ of personal attacks and distortions is unexpectedly impressively consistent too. Don't let me discourage you from instancing cogent examples any of my shifts of position, trolling or attacks in the face of your courtesy and consistent avoidance of my repeatedly re-stated basic points. A bit of serious investment of effort is good for developing intellectual integrity. And some other kinds as well.