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Post by cyrilr on May 11, 2020 15:28:54 GMT 9.5
Distillation should not prove very difficult. If you can operate, and run electric current through, a molten chloride electrolyte with molten cadmium, and scrape the actinides off it - and likely have to use distillation to separate salts and metals - then you can do a much simpler vacuum still. In any case we are talking full blown hot cells and high activity gas management. Throwing cesium-ridden spent fuel in a hot molten chloride bath... pretty nasty offgas regardless. Sr is not as big a contamination issue as Cs.
In any case the chloride electrolysis process has issues of its own, you end up with at least 3 additional waste streams: cathode, anode and electrolyte, with due processing and waste storage complications. Anode processing looks pretty hairy to me, and anything that processes the electrolyte, the anode or the cathode will itself become high level or intermediate level waste, and is hands-off full-blown-hotcell territory.
If we are going to bother with salts then zone refining would be an interesting option there as well, to remove some fission products.
For a still, 1400C would not be required, 800C should be enough to remove strontium and most of the barium. This is a vacuum still not atmospheric. Though a higher temperature design, using a refractory composite still (and possibly a separate, cooled, stainless steel vacuum vessel as pressure containment) would be interesting. In reality we'd likely want to run just above the fuel melting point at least anyway, it'll simplify the process to have a liquid actinide still bottoms that can be gravity drained to form the ingot for extrusion into new fuel elements.
Keep in mind too that zone refining involves melting - so high temperatures (and possible offgas issues) are there in any case. Given the small quantities of offgas and distillate it does not seem difficult to manage and immobilize. Cs can be immobilized by gettering to form a stable compound (CsF possibly, using CuF2 getter).
A combo of vacuum distillation and zone refining would be decent enough I think. Maybe not all lanthanides are removed, but in a fast reactor, that is not that important anyway.
A still of sufficient capacity for a 1000 MWe reactor would fit in a car's trunk. Tabletop equipment.
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Post by cyrilr on May 10, 2020 22:28:33 GMT 9.5
In theory zone refining would have mixed results. The actinides should have good solubility for each other. The lanthanides likely have good solubility too though so likely less effective. Things like cesium are not well soluble so are removed but then any baking would largely remove that already. Strontium could be somewhat effectively removed. Zirconium and molybdenum would not be effectively removed as they have good solubility, but Zr is already part of the metal fuel alloy and Mo is not detrimental.
Really needs an experiment - which is not that hard to do as one can start with depleted uranium and non radioactive noble metals, lanthanides, strontium etc. Transuranics aren't really necessary to add I think as there seems no reason to suggest they have low solubility in molten uranium so that will simplify the experimental setup.
For fast reactor metal fuel we'd obviously not care much about some lanthanides and Zr, Mo being left. If excessive amounts remain then it starts to become an issue at some point just due to physical high concentration in the fuel after many recycles.
Silver, cesium, strontium, could all be removed by distillation. Unfortunately most of the lanthanides could not as their volatility is often close to the TRUs (though this is a method to separate TRUs/lanthanides together from uranium).
Unfortunately I do not have the time or experimental resources to develop this technology. It would be a fun national lab project.
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Post by cyrilr on May 10, 2020 20:12:15 GMT 9.5
What's the Cheapest New-Build Power Technology? Aaron Larson 2020 Apr 29 Power Magazine www.powermag.com/whats-the-cheapest-new-build-power-technology/Using LCOE and installed capacity, it seems that on-site wind and solar PV win. However, something must be added for new transmission as well as appropriate backup. That’s an understatement; that “something” costs more than the wind and solar itself! Plus costs of that “something” rise the more wind and solar is added to a grid. What is more honest is to look at the total system cost of a hypothetical renewables only grid. Because if we want to meet ghg emissions targets we will need to all but eliminate fossil fuels. Talking about LCOE when you get 5% of your energy from solar and the other 95% being fossil fuel is obfuscation at best.
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Post by cyrilr on May 10, 2020 0:15:52 GMT 9.5
Flow batteries have always appealed to me, because of the various potentials (no pun intended) made available by having a pumpable electrolyte. Recycling would be easy, pump out the electrolyte to a pump truck and ship it to a recycling center, mechanical components can be repaired or replaced as normal.
Vanadium as mentioned is not interesting, these batteries use way too much of that and it's too rare and expensive for bulk applications.
Bulk grid storage isn't the first application that comes to mind, since that's a tough business. Low margins, low cost competitors (gas turbines). Small grids and remote applications would be interesting, especially for demands where a coal or gas powerplant would be too big, like a tropical island with some resorts (say a MW or less). Any grid that is powered by diesel and has good solar or wind resources could be interesting.
But a more interesting near term application would be transportation. If the power density is decent enough, it could be used for shipping and trucking, pump the electrolyte in and out for fueling, so recharging the vehicle or ship itself isn't necessary - same as diesel fueling. Anything that competes with diesel is much more $$$/kWh than bulk electric storage in a coal and gas grid.
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Post by cyrilr on May 9, 2020 22:33:10 GMT 9.5
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Post by cyrilr on May 9, 2020 19:49:12 GMT 9.5
Are there enough CANDUs to make that a viable re-use pathway going forward? Aren't they all planned to be replaced in a few decades anyway? There's potential to uprate and extend the life of the CANDUs but obviously there aren't enough. Then again if we want to replace fossil fuels globally we'd need at least 10x the current nuclear capacity. A lot of that - probably most - would be Gen IV. There's tons more options there for re-use. Fast reactors being obvious but there are some not immediately obvious options too. Fluorination to remove the uranium and then simply using the bulk fluorinator bottoms as fuel feed for a fluoride MSR is a great way to go. The mix is mainly TRU/lanthanide/noble metals and has a high fuel worth despite the high concentration of fission products. I suspect though that we will continue building Gen III and Gen III+ for a long while, and simply re-baking the fuel for re-use in a CANDU seems like a useful part of the solution. As long as we are still using billions of tons of coal a year I'm not picky on the flavor of nuke. All hands on deck.
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Post by cyrilr on May 9, 2020 19:37:46 GMT 9.5
A serious boner in that piece: “The typical nuclear power plant creates about 2,300 tons of waste annually,” reports Big Think.The entire US fleet makes about 2300 tons of HLW annually, not each plant. Indeed. The US nuclear fleet generates 92 GW, implying an essential waste stream of only 92 tons per annum of fission products. Of course, bean counting would have the industry minimise the cost of reducing used fuel down to its fission products, but 92 t/a is at least a very low minimum. It could be buried in a single borehole a year, as deep as the fearful require. The article from Oilprice is crap. Just more scaremongering of "ooh 2 million year half life! WHOPPING!". Gee what about the BILLIONS of TONNES of URANIUM that occur NATURALLY with BILLION YEAR HALF LIVES. WE ARE ALL DOOMED. Oh no wait. We're not. Granite rocks aren't a threat to humanity after all. Even though granite rocks will still be radioactive when our sun runs out of hydrogen to fuse. Then there is the nonsense about how the waste is vulnerable to terrorism. Really? Armored dry casks holding ceramic pellets in metal tubes in the middle of nowhere? What scenario is postulated here that would lead to a large number of casualties? How does one get a lethal dose of radiation to the nearest house? It's simply not credible, and alluding or suggesting that there is a big risk is absurd hyperbole and bad journalism. As usual articles like these don't even bother to elucidate. There is a mention of "a lot of WASTE". Oh scary. No attempt to explain the trivial amounts of actual fission products, or even what a fission product is, or the difference between high level and low level waste. Or indeed anything that would be useful to comprehend in order to understand risks. Just another article worthy of no better storage cabinet than the garbage bin. Then again do we really expect anything else from an oil website?
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Post by cyrilr on May 8, 2020 22:33:59 GMT 9.5
Actually algae are pretty efficient already at making lipids from sunlight. Yet they couldn’t compete with oil even at $200/bbl.
What matters most, is cost. Any reliable $/kg H2 figures?
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Post by cyrilr on May 8, 2020 17:06:19 GMT 9.5
I doubt it. I have heard of similar schemes and similar grand claims for decades, yet it never seems to get out of the lab. What gives?
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Post by cyrilr on May 8, 2020 17:00:35 GMT 9.5
The idea is to either add some 5% LEU for a hybrid fuel-repo fuel mix, or to use the fuel for CANDUs. In the Russian REMIX solution, the extracted fuel of say, 1% enrichment is topped up with (maximal) 20% LEU to provide 3.5% recycled fuel to go back in the PWR. The increase in mass is here 15%. That is quite tolerable, especially since the removal of the fission products has already reduced it by 5% or so. An attractive feature of REMIX is that at end-of-life most of the excess U238 is destined to be stored as the relatively innocent depleted uranium (DU), instead of the familiar and nasty reprocessed uranium (RepU), high in U234, U232 etc and probably traces of Pu etc. In contrast, in classic CANDU fuel all of the U238 gets irradiated and almost all of it ends up as RepU. For sure a higher enrichment top-up would help, but it's getting more and more difficult to get 20% LEU, especially commercially for large scale power production. Many enrichment facilities aren't licensed over 5 (some 7%), a lot of the 20% LEU comes from downgraded weapons grade material which is a finite and small source for bulk power production levels. I think the CANDU approach is the best, as it avoids a higher fissile top-up and has other advantages that could lead to large uprates. It would also have the highest proliferation resistance, with ThO2 additions making U232, U233, U234, plus the U235 and U236 in the fuel it would mean impossible isotopics for weapons grade (even if the uranium would be separated).
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Post by cyrilr on May 8, 2020 5:04:37 GMT 9.5
Let a thousand chemistries bloom... very poetic, spoken like a true mad chemist! Though one can't go too crazy - in a regulated industry like nuclear, having too many options leads to lack of focus and cost efficiency. As the French proved with their PWR focus - you can pick between big, bigger and biggest PWR! Not a huge fan of their PUREX MOx work though, it's a dead end old dog tech, too big too messy.
As for cutting it in half... sounds like a decent start. Perfect is the enemy of done. I'll say that in favor of the French MOx work even. In any other industry, doubling the amount of energy you can generate from a resource, with the same amount of waste, would be considered a big achievement.
But you're right, the CANDU path seems more promising. Any engineer would be able to appreciate the entropic advantage of adding ThO2 to the recovered spent fuel rather than diluting enriched uranium into it.
As to why ThO2 is not used as a burnable poison - it does have some downsides for that particular application. Gad is really high worth so little is needed. Thorium is very low cross section by comparison, so a bunch would be needed. That then displaces natural uranium so it lowers the fissile loading. It also generates U233, a rather superb fissile. Good for fuel economy but maybe not for a poison application - one can end up with too much worth at end of life. For a recovered fuel mix it makes a good deal of sense to me as the recovered U + TRUs have a higher worth than natural uranium.
Plus one can do the opposite trick of enrichment zoning. This has always been an issue with CANDUs. Reactors have a natural Guassian power distribution, so the edge channels don't want to make much power. Since thermal-hydraulics limit power output, the leading pins become limiting. With natural uranium one is limited to the 0.7% U235. While ideally one would have more fissile in the central pins of a channel, and in the outer channels of the core. By using slightly enriched uranium, or a more reactive fuel mix with poison (thorium) added variously one may better optimize the power output. This could mean a 20% power increase. Combined with a square calandria (why not, there's no pressure) one can generate another 25% more power for a 50% power uprate. 900 MWe out of a 600 MWe reactor with the same core width sounds like a big deal.
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Post by cyrilr on May 8, 2020 0:29:29 GMT 9.5
Thanks for the additions, E-P. You are correct, as usual.
Not too sure about the radiolysis being trivial; generating oxygen in a closed loop system (can't just vent to atmosphere, obviously!) and water that reacts exothermically with the rocket propellant oxidizer... depending on the rate it could probably be designed for.
My point being rather to attempt to avoid hydrogen chemistries (including water, HNO3 compounds etc.). So to me things like vacuum baking, vacuum distillation and zone refining (latter two more for metal fuels) are better avenues of approach.
Of course there is not sufficient reactivity left with the uranium and TRUs left together. The idea is to either add some 5% LEU for a hybrid fuel-repo fuel mix, or to use the fuel for CANDUs.
An interesting option I think would be to add some ThO2 and make a CANDU fuel mix; even with the lanthanides in there is actually more reactivity than natural uranium, the ThO2 brings that down while yielding good fuel burnup later via U233. The ThO2 could be varied radially and axially across the CANDU core for power flattening, equivalent to enrichment zoning, yielding at least a 20% uprate to reactor power. All without any more uranium having to be mined...
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Post by cyrilr on May 7, 2020 17:33:18 GMT 9.5
It contains water, and tons of hydrogen. ... Actually in freshman Chem lab, 6 hours per week for 3 quarters, we used pubchem.ncbi.nlm.nih.gov/compound/Nitric-15N-acid-solutionwhich also has a tiny bit of water. Either way, the oxygen in the oxides will instead combine with the hydrogen, once everything is cool and so all the actinides and the interesting fission products have formed separate precipitates. Except those elements that remain in solution,the solution being less acidic. I don't know whether or not this is a good idea for nuclear waste management, but it certainly offers possibilities. You mean if it doesn't radiolyse and form combustible gasses, or go critical with all that hydrogen, and if no water enters into it accidentally which will cause it to explode. You do realise this stuff is rocket propellant right? It's unstable? Not radiation resistant? We need to make nuclear reprocessing safer so it can be cheaper. Starting off with mixing rocket propellant in with the spent fuel is not a good start.
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Post by cyrilr on May 7, 2020 16:25:58 GMT 9.5
It contains water, and tons of hydrogen. Let’s not split hairs here. Rocket propellant isn’t the first thing that comes to mind we should use to recycle spent fuel!!! That is just another example of the craziness of nuclear chemists.
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Post by cyrilr on May 7, 2020 3:31:50 GMT 9.5
a major physical limitation of solar power... the large area needed is a physical limitation One might say that renewable energy consumes significant non-renewable resources. That's a contradiction that the believers cannot see. It's an excellent point that is rarely communicated. Sure, the sun will shine for the next billion years. Now calculate how many solar panels we'd need to power the world for the next billion years, and how much non-renewable resource that requires. Solar enthusiasts have been chiding us forever about the longevity of nuclear waste. How about the longevity of non renewable resources used to make short lived renewable generators into the same timeframe of the future? A million years from now all the nuclear waste will have decayed to harmless levels. How does that compare to the non renewable resource use and attendant, forever-toxic wastes created by the fabrication, installation, use, and recycling of renewable energy?
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Post by cyrilr on May 7, 2020 3:23:42 GMT 9.5
Just use 'red,fuming' nitric acid plus moderate heat. It is hard to see that a process that creates an aqueous solution of plutonium from unspecified fuel rods is anything but proliferating. Several years ago, CyrilR proposed – correct me if I'm wrong – that (oxide?) fuel could be heated to high temperatures that separated off the most volatile fission products, leaving the plutonium still in the uranium matrix. Non-proliferating. Since the baked fuel is still in pellet form it can go directly into a fresh fuel assembly and returned to the reactor. Correct. And don't remind me of the endless flow - tempus fugit and all that. But that idea still has merits, in my opinion. If we want to recycle oxide fuel into oxide fuel, why not point out the obvious and stay with oxides. Not that anyone listens to me. Even OREOX, as proposed for DUPIC, which comes close, is too complicated with valence-state changes. Some sort of simple low speed grinding and attrition process should suffice. We have UO2, we want UO2, why not stay with UO2. Indeed, major issues of PUREX and its cousins have arisen from the obvious facts: * criticality problems (acid is mainly water) * radiolysis problems (acids are NOT radiation resistant) * secondary waste generation and contamination problems (plutonium has extremely complex chemistry and will go all over the place, in the waste bin, in the product bin, on your equipment) which then cost a fortune to clean up and generate secondary wastes that cost even more to clean up. *etc. etc. What can I say? I'm shouting in the desert. Them chemists love their acid. Perhaps they are ON acid. Or just being deliberately obtuse - one hardly sees strategy in proposals that make oneself (and your program managers) redundant. If you're a hammer everything looks like a nail, and if your business is selling hammers you won't be promoting screws even if they are superior to nails. I'm sure that if a nuclear chemist were in charge of designing a steel recycling plant, he/she would suggest we start by dissolving the steel in acid, and then... The idea could also be applied to other fuels: alloy fuel such as used in the IFR, where possibly one would melt the fuel in an electrically heated, vacuum furnace (perhaps in a thoria crucible or such). Be a lot simpler than the electrochemical process with cathode processing and nasty biles of electrolyte, anode slime... yuck. Better than acid I guess, but that's not a high standard. In metal fuel there would be less concern about the lanthanides staying behind - up to a point. At some point one does end up with too much physical concentration of lanthanide in the fuel and another process would have to be used - zone refining, perhaps, keeping with the no chemical change theme.
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Post by cyrilr on May 7, 2020 3:08:22 GMT 9.5
Interesting idea. Makes sense, on first blush: the virus' single-strand DNA (RNA) would be much more sensitive to ionizing radiation - effectively all breaks are the equivalent of double strand breaks (which also serves as example of why a virus can mutate quicker than eukaryotes). In addition, a virus lacks several of the repair/defence mechanisms of eukaryotes. Especially multi cellular organisms which also have cell mitosis as final defence mechanism - not an option for a virus, clearly! Based on UV treatment units' effectiveness in removing viral threats, the idea seems promising. It would probably require a number of treatments in series to be most effective for viral agents inside an organism, though.
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Post by cyrilr on May 5, 2020 15:46:36 GMT 9.5
Cs is just one fp. What about rare earths and noble metals? Any single stage process will require a high decontamination factor for all fp.
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Post by cyrilr on May 5, 2020 15:12:32 GMT 9.5
Interesting, but what happens to the fission products? To what extent are they incorporated into, or stick to, the crystals? What is the decontamination factor?
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Post by cyrilr on May 3, 2020 0:49:49 GMT 9.5
The term "foibles" relates to a minor weakness.
Power that isn't there 80% of the time and can't be turned on when needed is hardly a minor weakness. It's a major physical limitation of solar power. It's physical so intrinsic - it won't go away no matter how much innovation. Similarly the large area needed is a physical limitation from the diffuse, low energy density nature.
These are not foibles. They are massive physics issues!
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Post by cyrilr on May 3, 2020 0:46:51 GMT 9.5
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Post by cyrilr on May 3, 2020 0:43:25 GMT 9.5
Or balcony railings:
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Post by cyrilr on May 3, 2020 0:42:05 GMT 9.5
Might be interesting as highway sound barriers.
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Post by cyrilr on May 3, 2020 0:40:25 GMT 9.5
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Post by cyrilr on May 3, 2020 0:40:02 GMT 9.5
Talking about vertical PV. This seems like an interesting concept, bifacial panels vertically mounted. It generates at a higher capacity factor and dual peaks that closer match the demand of morning and evening spikes.
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Post by cyrilr on May 2, 2020 18:09:58 GMT 9.5
Given how long buildings last ... Plenty being built in Asia and Africa. Which is mostly additional demand, rather than replacement of existing buildings. And again, virtually all vertical surfaces, most of which not even sun facing...
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Post by cyrilr on May 1, 2020 20:17:04 GMT 9.5
... virtually all sun-facing windows are vertical ... Future architectures might be different. Given how long buildings last this makes the whole concept irrelevant then, in our lifetimes.
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Post by cyrilr on May 1, 2020 20:16:22 GMT 9.5
Yeah that'd be pretty cool to see. Still virtually all sun-facing windows are vertical, as a rule, so that dampens my enthusiasm a bit. Here in Holland a properly installed PV system facing south at correct angle and no shadows has about a 10% capacity factor lifetime. Going vertical and accounting for some shading would get you only a 6-7% capacity factor. Pretty dismal. Maybe good for sky scrapers in Dubai. Will it work with a low e coating though? Or will that coating drop output further? You are going the wrong way. The closer to the equator the worse the performance for a vertical array. T2M
And the further from the equator the lower the solar insolation to begin with. Most buildings and glass are not close to the equator, either...
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Post by cyrilr on May 1, 2020 18:31:40 GMT 9.5
... windows are vertical ... I have a skylight. Yeah that'd be pretty cool to see. Still virtually all sun-facing windows are vertical, as a rule, so that dampens my enthusiasm a bit. Here in Holland a properly installed PV system facing south at correct angle and no shadows has about a 10% capacity factor lifetime. Going vertical and accounting for some shading would get you only a 6-7% capacity factor. Pretty dismal. Maybe good for sky scrapers in Dubai. Will it work with a low e coating though? Or will that coating drop output further?
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Post by cyrilr on May 1, 2020 18:11:22 GMT 9.5
Sounds cool, but it has an obvious problem: windows are vertical, a horrible angle for solar panels (unless you live on the north or south pole, but there’s little solar there to begin with) This will further reduce the already dismal capacity factor of pv.
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