DoE digs up molten salt nuclear reactor tech, taps Los Alamos to lead the way back After more than 50 years, molten salt nuclear reactors might be making a comeback. The US Department of Energy (DoE) has tapped Los Alamos National Laboratory (LANL) to lead a $9.25 million study into the structural properties and materials necessary to build them at scale. "The US needs projects like this one to advance …
I appreciate that it is a bit different (in pressure, temperature, toxicity, radioactivity and many other hazardous parameters) but I'd always wondered how wave solder machines heated up their tank of solder given that presumably the pump blades and everything were fully immersed and therefore embedded in the solid solder?
For wave solder machines, you simply turn on the pot heaters a few hours before you need to use the machine. Ours needed about 4 hrs to get to temp, but I always felt better letting the temperature stabilize for couple extra hours, we seemed to get better results.
The controller won't allow the pumps to run if the solder temperature is below temp, preventing damage to pumps and motors.
The controller software had a built in timer so that the pots could begin warming up overnight. I forget the break even point, but if you only ran the machine a couple times per week it was most economical to shut down between runs. At some point it becomes more economical to keep the pot at temp all the time.
Interestingly, our lead free (SAC305) machine would get to temp faster than our leaded machine, despite the higher melting point of leadfree. I thought that we might have a defective element, but then I did the math. SAC305 has a lower heat of fusion than 63/37 tin-lead.
The initial filling and heating of a new solder pot is the trickiest part. You worry about burning out elements if they have a void near them, so you pack the pot as full of solder bars as you can before turning on the heat (in retrospect, I should have pulled the pumps out first) and then you babysit the pot while it heats, adding more solder bars as the level drops.
My guess would be, extremely slowly. Days, weeks, whatever it takes. Maybe run the reactor at very low power until the salt is melted?
There are a whole bunch of industrial processes that are extremely messy if not outright impossible to restart, if you stop them abruptly. It's a significant problem, but not a showstopper.
"There are a whole bunch of industrial processes that are extremely messy if not outright impossible to restart, if you stop them abruptly. It's a significant problem, but not a showstopper."
I once worked on a control system for an oil pipeline in India. AIUI, if the pumps fail and the oil stands still in the pipe, it solidifies and that's that.
That doesn't seem right. Why aren't there abandoned oil pipelines filled with solidified oil all over the world if that's the case?
Ukrainian operatives sneaking into Russia to damage pumps on Russia's oil pipelines would be a winning strategy, by denying them money to fund their "special operation" as it would take years to build a new pipeline alongside the now-abandoned one...
Though after seeing video of what the Canadian "tar sands" oil is like I have wondered how the heck it is possible to get that through a pipeline at all, as it is practically a solid already.
Anything involving large volumes of molten chocolate...
A few years back I worked for a specialist haulage contractor that mostly handled nasty chemicals, but also shifted liquid chocolate around Europe for a famous confectionery company. One day a rig came into the yard hauling a tanktainer full of the stuff - with a failed heating system. The heater can keep the load liquid long enough to get it from point A to point B, but no way can it melt it again if it solidifies. That problem was solved essentially by a bloke with a hammer and a chisel, resulting in a downgraded tank and a large pile of chocolate rubble that was free for all takers.
Five tanks full of latex that RENFE shunted into a siding and forgot about didn't fare quite so well.
I wonder whether the radioactivity of the uranium fluoride component is enough to heat the salt mixture to its melting point? By the sounds of it, it's a mixture of a bunch of salts, and not a single one, which chemically speaking will lower the melting point, as long as those salts are miscible (otherwise you'll get one or more of them precipitating out at their respective meting points).
As a rule of thumb, a mixture of two compounds will melt at a lower temperature than either individually, because the entropy of the (disordered) molten mixture will be much higher than that of a (highly ordered) co-crystalline phase.
If these things aren't molten to start with, I'm guessing the start-up procedure would be to heat the reactor vessel to above their melting point, melt the salts separately, and pour them in. I suspect the reactor vessel would have a big old heating element in its base for this purpose.
From the article:
"Cooling was also achieved using a fluoride salt mixture, but it lacked the uranium and zirconium found in the fuel."
So there are two separate molten salt loops, the core loop with the radioactive material added and the cooling loop that doesn't have radioactive material.
"So there are two separate molten salt loops, the core loop with the radioactive material added and the cooling loop that doesn't have radioactive material."
The LFTR design has core loop and a blanket loop. Both are radioactive, but have different chemistries. I'd have to review some of the reference designs to see how the cooling loop was implemented in the early testing and what new designs have been proposed. One design for the power conversion was to use CO2 to drive a turbine in a closed loop rather than steam. It can be more efficient and lead to longer turbine life.
"The molten salt is the coolant and the core. Drain it into a tank and it's still a nuclear reactor."
The idea with LFTR is that the capture cross section for fast neutrons is too small to maintain a chain reaction so if you move the molten salt to a tank without a moderator to slow down neutrons so the much larger thermal spectrum cross section takes over, the reactions cease. Part of the safety system is a drain at the bottom of the reactor that is blocked with a salt plug that's kept cool. If something happens, that cooling is removed, the plug melts and the liquid salt drains into a capture tank where the reaction comes to a grinding halt.
Presumably, it's kept just above criticality by slowly feeding in the fuel component of the salt, so stop adding fuel, and the neutron flux falls until the mixture is no longer critical. No, it's not just "turning it off" like a switch, but do you think a coal-fired plant can just be turned off either?
Not molten salt - but the USSR designed submarine reactors in their Alfa boats using a eutectic lead-bismuth coolant (melting point of about 125C) in the primary loop.
These reactors had to be connected to an external steam source when tied up to keep the coolant from freezing. In service, this proved near impossible with the steam supply often being unavailable, so the reactors had to be kept running which meant they couldn't be maintained. And if they broke down, the reactor couldn't be restarted.
Four of the fleet were decommissioned because their reactor coolant froze. All of the submarines are now out of service.
Not quite the same thing, but I've seen videos of a bit of plant being dismantled because something went wrong and the "stuff" set in the pipes. As the "stuff" was nuclear waste going through the vitrification process to render it immobile prior to storage, dismantling wasn't done by a couple of blokes in boiler suits.
It was interesting watching the plant, which wasn't designed for dismantling by remote manipulator, being taken apart by a remotely controlled vehicle with manipulator arm on it - taking things apart (with a power hacksaw at times), then dropping the bits in bins, and finally vacuuming up all the "dirt".
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What's wrong with "atomic scale"?
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Other criticisms include the lack of background research:
MSRE at Oak Ridge was actually an operational reactor and produced around 8MW for four years:
https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment
China will probably be starting its new 2MW design later this year.
https://en.wikipedia.org/wiki/TMSR-LF1
Atomistic refers to things being composed of other indivisible things, or being broken into groups. Ie, "an atomistic media landscape'.
For describing something as being of the size of atoms, the phrase 'atomic scale ' is more appropriate.
Atom means indivisible, but whoever borrowed the term from the Greeks did so before modern nuclear physics.
If the world had developed Throrium instead of Uranium, then maybe we'd be damn close to emissionless power by now.
Especially as the UK was a world leader after (and during WW2).
However, bombs outweighed peace and here we are.
Little factiod for those interested in geopolitics. The next few years are going to see the big players* working towards energy autarky.
*A phrase that now excludes the UK as per democracy.
In my days in nuclear research, the matra was "yes, we could have Thorium and molten salt cooling, but nobody is paying for it, pwr's and bwr's have been paid for by cold war armament programmes". All the old hands thought we would need another war, cold or hot, to get the requisite funding, unavailable in peacteime.
Are we going to war with China (or China with us) or is China's combination of energy thirst, available funding and manpower in R&D and manufaturing big enough to pull it off without the requisite underlying military conflict?
The moment any power (not necessarily country) becomes self-sufficient in energy, the entire map of the world changes.
Ironically, the lesser developed counties are probably closer as their demand is considerably lower.
The trick is to have enough electricity. With enough you can make gas and oil. The recent news about extracting kerosene from air+sunlight shows that.
We're so far into the game that at this point, I would view any country (power) trying to achieve energy independence as a hostile act. Luckily the UK has as much chance of that as it has of moving 1000 miles southward, so we're safe.
The US is energy self sufficient and has been for most of the past decade. Sure we do import some oil but we export more oil and natural gas than we import.
Energy is fungible, so unless you ban export you are still part of the world market and still respond to shortages. For many years the US had a ban in place on exporting oil (but not refined products like gasoline) but that was lifted a few years ago because we were producing more oil than we were using and the oil producers said they would have to end investment in new projects. They've (mostly) ended investment in new projects since the pandemic anyway, so I think we should return the favor by banning exports once again. At least our oil price would be a bit more independent of the world price for our trouble.
"Energy is fungible"
Only in a most general way. Oil is not fungible. "Oil" describes a wide array of substances. In terms of petroleum, there are all sorts of grades that are useful for certain things. Refineries are built to process only certain types of oil. Light-Sweet is preferred since it contains a higher amount of fractions used for transportation fuels. The Sweet description relates to the amount of contaminants that must be removed. Heavy oil is quite thick with longer molecular chains. To use heavy oil to make petrol or jet fuel, it has to be cracked. If it's also sour, more processing must be done to separate out the contaminants. The upshot is you can't pump Heavy-Sour oil into a refinery that's set up for Light-Sweet crude. It also means that in the US, some of the oil that's produced isn't compatible with refineries in the US and since no new ones are being built, it might not ever be able to be processed so it's exported. If it couldn't be exported and appropriate oil imported, oil companies wouldn't develop their finds that show the wrong stuff.
All the old hands thought we would need another war, cold or hot, to get the requisite funding, unavailable in peacteime.
Well, there's a "Special Military Operation" going on right now that's making lots of people very nervous about the idea of relying on Russian oil and gas. Maybe that'll count.
Are we going to war with China (or China with us) or is China's combination of energy thirst, available funding and manpower in R&D and manufaturing big enough to pull it off without the requisite underlying military conflict?
My interpretation is the latter.
As I interpret how things have gone/are going, the ruling classes there see technology as the path to dominance. They've made a shedload of money off us from undercutting everyone else at mass production - effectively with slave labour pay and conditions. Lately they've been splashing the cash about - but they have a policy of technology transfer as a key part of big projects. Along the lines of "yeah, we'll help you out funding ${big_project}, but in return you need to transfer know-how to us". So that gets them the know how fairly quickly without having to start from scratch.
Then they have a "planning system" that's very different to ours. Over here, someone wants to build a nuclear power plant - masses of objections, protests, public enquiries, and years of delays. Over there, the ruling classes decide where and when it's going to be built, the locals accept that or ... disappear.
A few years ago I was at a talk, and it was described how they were in the process of throwing up a number of Westinghouse design plants - to a timeframe unthinkable over here. And it was expected that they'd achieve both the timescale and budget planned.
So largely I think it's a recognition of the benefits, plus the ability to make things happen.
"Are we going to war with China (or China with us) or is China's combination of energy thirst, available funding and manpower in R&D and manufaturing big enough to pull it off without the requisite underlying military conflict?"
Given the really bad pollution that China has been experiencing, the cost savings in medical care will likely pay off the work in MSR's. Getting rid of coal also means getting rid of an import that can be used to control the country. Thorium is all over the place and China has been a leader in Rare-Earth metals by taking away the expensive disposal costs that mining companies in places like the US would have to pay and have been stockpiling the Thorium that comes with the heavier end of the Lanthanides. The US could be doing this too and store the Thorium in Nevada where they are already burying all sorts of undisclosed stuff on the former nuclear bomb testing range.
China's first thorium reactor only makes 2MW of thermal energy, generating even less electricity. "if the experiments are a success, China hopes to build a 373-megawatt reactor by 2030, which could power hundreds of thousands of homes."
It's fine and important to research and develop nuclear power for possible mass construction to meet energy needs over a decade from now. But all the nuclear fans blathering about how we need to build it now live in an alternate reality where France kept building more nuclear reactors and Toshiba and Westinghouse got better at building AP1000s faster and cheaper instead of going bust.
Yeah, I don't think the current nuclear industry is designed to actually productise innovative technologies into real, running, commercial reactors. It is designed to waste enormous quantities of money and time in forever-delayed projects, while funneling some of the money to suitable pockets.
No need to worry about the long-term waste and the likely too-optimistic models for handling it, if the waste generation never starts (along with the electricity and heat generation) - much more profitable and certainly less risky to always stay in the design or build phases. Only need a couple of iterations of new design->lobby for it->start building a pilot->face problem after problem->redirect funding in order to remain gainfully employed for your entire career without ever generating a single watt of electricity from your reactors.
"Yeah, I don't think the current nuclear industry is designed to actually productise innovative technologies into real, running, commercial reactors"
A big part of the problem are the regulatory agencies. MSR's are "unproven" technology so getting the required permission to develop them is nigh on impossible. The Cart and Horse problem. Governments are exceptionally good at that sort of thing. Reactors are too expensive to develop to have such a high chance of being shot down by functionaries with no experience in engineering to pump money in to the projects. It's much easier to stick with what's allowed and sell very expensive fuel forever.
However, as the Oak Ridge National Laboratory found during the Molten Salt Reactor Experiment, fluoride salts are incredibly corrosive
I'm not sure they needed to test for this, any chemists on board would already have known this. All salts are corrosive, incredibly so in their liquid forms. The only real solution is to keep them in containers which are inert to their components, which is usually some form of glass, though glass is noticeably unsuitable for fluorides which tend to leach.
Anyway, any kind of reactor that needs extensive cooling is going to need water at some point and this is becoming a bigger risk as sources of plentiful water become scarcer.
Anyway, any kind of reactor that needs extensive cooling is going to need water at some point and this is becoming a bigger risk as sources of plentiful water become scarcer.
Nuclear reactors use seawater for cooling, and there appears to be no potential shortage of seawater.
For that matter, if you had enough energy then you could run desalination plants and create fresh water by stripping the salt out of seawater.
It does raise the question, "why fluorides?"
Fluorine chemistry is generally pretty nasty, due to fluorine being the most electronegative element and thus having a propensity to grab electrons off things that are normally considered inert (such as xenon).
I suspect the reasons here are due to the exact physical properties of those salts (melting point, heat capacity, and so on), but I am left wondering why they don't choose to use less "nasty" salts such as those of other halogens (chlorides, bromides and iodides).
Of course, this could also have something to do with the nuclear properties of fluorine - I don't have a great deal of background knowledge of nuclear physics, but is fluorine more tolerant to having extra neutrons thrown at it for example?
edit - A quick google suggests that the stable isotope of fluorine is 19F, so if this were to capture a neutron, you'd get 20F, which decays quickly via beta emission (a fast electron) to stable 20Ne. Since salts are conductive, that electron is easily dealt with, and presumably the neon just diffuses out and can be siphoned off. I'm guessing you won't be getting any fission products from fluorine, but if you do, I'm also guessing that being light elements, their isotopes will be either very short-lived, or stable and easily dealt with too. I suppose salts of heavier elements would be more likely to produce all sorts of daughter 'topes.
"If you look into the ORNL reactor, they had a series of processes to filter off various reaction created contaminants and then process them to be refed back into the reactor."
That's where they left off, the continuous reprocessing elements without going too far into the specifics. One or two iterations and they would have worked out and proven the full system as conceptualized. It's was too bad that it didn't create Pu in bomb making quantities or transuranics much at all.
The point of the reprocessing setup was that only a small amount actually needed to be done (only to remove non-gaseous poisons which might stop the reactor and only if they built up to levels actually needing to be dealt with)
In most cases it would be easier to knock a few points off the overall economy of the reactor and simply enlarge it a little/overfuel it slightly (the reactor was continually fuelled as needed, rather than being loaded with 12 months supply at startup) and calculations for larger designs pointed to the processing only being needed from about 10-15 years in
The primary reason this is finally getting some attention is that China's replicated the MSRE at Wuwei and has had it running since last October whilst simultaneous preparing a 100MWe larger unit (the ORNL scaled up proposal). It's no longer possible for the US establishment to pretend it doesn't exist
"All salts are corrosive, incredibly so in their liquid forms"
Only if they become ionic items (ie, dissolved in something else)
The whole point of molten salt is that the salt itself is the liquid (melts at 450C) and the FliBe used wasn't water soluble
ie: This isn't a "salt water loop", the salt IS the loop, running at 650C and capable of excursions out to 1000C quite safely
Some of the comments (and the article!) seem to be based on some lack of knowledge on how Liquid Fluoide Thorium Reactors work. For example they don't use water coolant in the primary circuit, but probably would use it in the secondary circuit to drive steam turbines. Uses a lot less water as this can be nearly a closed circuit with recovery.
Anyway, a simple YouTube explanation https://youtu.be/nYxlpeJEKmw as a starter
Yeah I came here to say that. The water in the primary circuit of a water cooled reactor is a closed loop, it is never used up. You wouldn't want water that has had direct contact with the core going -anywhere-, obviously!
TFA is extremely misleading on the water argument, so much so that some anti-nuclear types could use it to complain about false benefits.
The benefits of molten salt reactors are not about water use (you would site them on the coast like any other reactor) the main benefits of MSRs are, THEY EAT NUCLEAR BOMBS, and THEY EAT NUCLEAR WASTE. Most normal nuclear reactors consume about 3% of their fuel before it is considered 'spent', whereas MSRs can reach 50%, i.e. more than 10 times more efficient use of the fuel. They consume nuclear waste from other reactors and ageing weapons stockpiles, as fuel - you basically dissolve the warhead in the salt, and its energy is burnt off slowly and safely over decades.
We have enough spent fuel rods, plutonium stockpiles, and 'dud' warheads to power the world for centuries, we would never need to mine or enrich new uranium again, or at least that's the idea.
However, I am sure that the anti-nuclear lobby, which I am convinced is funded by the sorts of companies that made 3 billion a month recently in the UK, will once again step in to ensure that the world chokes on CO2 from coal, oil, gas, and tree-burning..
Yes, the evil cabal of fossil fuel companies and aging anti-nuclear hippie enviros successfully infiltrated the construction companies building every nuclear plant to make them all billions of dollars over budget and a decade late.
Awful financials has doomed the current generation of nuclear plants, and It seems the next-generation technologies won't start producing > 100 MW electricity until 2030, with actual proof that they will be cheap and quick to build coming after that.
Not necessarily the construction companies, but the governments and regulation bodies who set the rules, certainly.
There is a running joke in the nuclear industry that the ONR, NDA, UKAEA, IAEA and AWE are 2/3 staffed by CND fifth-columnists. (and I say the CND is staffed by oil industry fifth-columnists.)
With the rules that come out of those regulators, it's easy to see why people say that: The ONR refuses to set a safe limit on radiation emissions from nuclear plants, knowing full well that physics means that gamma rays can't be completely 100% shielded by any depth of concrete - it sets a wishy-washy principle known as "ALARA" (As Low As Reasonably Achievable") which creates a ratchet-effect of stacking safety factor on top of safety factor, only ending when the project is at the edge of feasibility. (they specifically exclude cost as a factor in deciding whether something is reasonably achievable or not)
They also use a completely daft model (the so-called Linear No-Threshold model) for estimating harm caused by radioactive release to the environment. It assumes that any radioactive material spread over the earth, however diluted it is, is just as likely to kill someone as if it were in concentrated form. That's complete nonsense - all the scientific research says that radiation is only dangerous above a certain threshold (as with sunburn), and below that, DNA in cells is able to repair itself. There's even some evidence to say that this process of DNA repair is beneficial to health. After all, life has always had low doses of radiation in the background.. Modern chemicals and nanoparticulates not so much, but no such extreme regulation applies to other industries which pollute the environment on a horrendous scale. (see this book by two pro-nuclear greenpeace activists: https://climategamble.net/)
As a result, you have utterly daft situations whereby the nuclear operators end up spending billions and making their emissions way below background levels just for someone to come along and suggest a new and very expensive way of reducing them even further, and they are legally obliged to delay their project while they report on whether it is reasonable for them to implement it. Meanwhile the fossil fuel industry emits more radioactive material (though trace amounts of Radon in the billions of tonnes of Oil, Gas and Coal that they burn through each year) than the entire history of Nuclear Fission. Accidents and bombs included!
I used to work for UKAEA at Culham - they once declared a major incident after someone brought in a gas lamp mantle - it was far more radioactive than any of the sources they were allowed to use.. Their sensors would register a spike if you went too close with a bag of Brazil nuts.
According to the dosimiter badges, the staff on site who receive the highest ionising radiation doses are those who work on the security gate, because they catch more cosmic rays than those inside the building.. If you accidentally bring your dosimiter badge with you when you go on a long-haul flight, it will be picked up by Health Physics and you may not be allowed on site because you have exceeded your radiation dose.. Cabin crew receive thousands of times higher doses than nuclear workers are permitted to take. It's utter madness. That is why nuclear is so expensive, the regulations are stacked against it.
That's also one of several reasons why it's so much cheaper and quicker to implement in China...
In AUS, the soviet-line communists ran a successful political party called the Nuclear Disarmament Party, formed to prevent uranium mining and power. The muscle was provided by a wide array of Australians of various stripes (mostly anti-government protest voters of one kind or another), but the backbone was Moscow-aligned communists.
The party collapsed in disarray because the membership wanted to condemn Russian nuclear arms and development (as well as Australian and American), and the organisation refused to allow that.
"Awful financials has doomed the current generation of nuclear plants, and It seems the next-generation technologies won't start producing > 100 MW electricity until 2030, with actual proof that they will be cheap and quick to build coming after that."
Once the design is all worked out, I'll bet the Chinese will have been designing for manufacturability the whole time so they can use their considerable manufacturing capability to crank out MSR's in the same way they have been building coal power plants. They'll also file a whole raft of patents too. While China isn't known for respecting intellectual property from outside entities, they will certain use EU and US courts to enforce the patents they are awarded. Thorium is a much better nuclear fuel and if MSR's are built that can use waste fuel from PWR plants as an additional source, the cost to run the power plants might be exceptionally cheap. If MSR's lead to good ways to produce therapeutic radio medicines, that might be another huge revenue stream.
they also eat thorium - which is the primary waste product of rare earth mining,
So much so that this changes the world's rare earth mines into thorium mines with a rare earth side gig
_VERY_ cheap fuel ($100-200/kg vs $50-75k/kg) and a benefit for other industries
There's enough thorium in old coal power station ash slurry to be wrth mining that too - which would essentially fund cleaning up such sites
water wouldn't even be in the secondary loop, eeither tertiary or quartenary
The advantage of this is that a steam explosion - is JUST a steam explosion (anything nuclear stays in the reactor building and anything that gets out of the primary loop only goes a few inches before freezing solid)
It's pretty clear that China's work on these units is intended to make drop-in replacements for coal burners in their existing recent power stations and they're chasing scaling from the 2MW Wuwei experiment to 100MWe before jumping to 1000MWe
The fuel salt is never allowed to solidify. It is introduced to the reactor vessel as a liquid and drained as a liquid. There is a primary circuit that contains the fuel salt (salts of fissile materials) which transfers heat to a secondary circuit of non-fissile salt, which then transfers heat to a tertiary circuit of water that produces steam to drive the turbines that drive the big alternators. It's no different to any other nuclear reactor. It requires power from outside to power it when it is not generating. The advantages of MSRs are size, cost, ease of refuelling (normally an ongoing process) and safety. I believe that nobody has yet built a commercial MSR.
As for being "clean", they aren't. They are low carbon though which is good for our immediate problems, but longer term we need to find a way to deal with radioactive waste safely, or ideally only produce waste that has a low-ish half-life.
longer term we need to find a way to deal with radioactive waste safely
Isn't that exactly what thorium bed reactors do? Feed highly radioactive isotopes in as part of the fuel mix, get "inert" ones out + some power.
The real problem is how to deal with medium level waste (tools used to handle fuel, for example) and low level waste (lots of lightly contaminated disposable gloves, and so on). The volumes of these far outweigh the spent fuel from conventional reactors.
The designs of current reactors are an inheritance from the fact that they were originally intended only to produce power as a side-effect, and TPTB were more interested in breeding plutonium.
"It is introduced to the reactor vessel as a liquid and drained as a liquid"
The entire loop (pipework, reactor and heat exchanger) is wrapped with electrical heaters. Freezing in the loop is permissible and part of the design criteria (it's used for things like isolating sections of the pipework)
With molten salts carrying the fissile material, the energy, and the waste products you have the tantalizing possibility of continuous flow processes for maintenance as opposed to the suck-squeeze-bang-blow approach with reactors which have fuel 'assemblies' of one sort or another. These are a bit of a nightmare all round.
This was part of the planning for ORNL's conceptual 1GW MSR power plant. IIRC they planned to divert a fraction of the flow, bubble F2 through it to strip some chemical and then another loop with molten bisumth to deal with other elements. Which is quite attractive.
The driving force for the whole MSR programme was to build a nucleer powered aircraft. The trouble was there's a Xenon isotope with a huge absorption cross section builds up. It's buildup was implicated inthe Chernobyl accident. The efect is a bit like keeping the foot brake on a car down, building up the revs and then suddenly taking the brakes off. Not good, and one of the reasons every 18 months 1/3 of a PWR''s fuel load has to be replaced.
Xenon, being a gas, simply bubbles up to the surface and can be blow away in the Argon cover gas.
"The driving force for the whole MSR programme was to build a nucleer powered aircraft."
That was the rouse to get funding. It came out later that Alvin Weinberg never even considered putting any one of his designs in an aircraft. They did have to make some drawings showing a reactor in an aircraft to present. It's the same thing you get today with computer graphics and animations of things that will never work in the real world. Those just get used to bring in loads of investments that the C-Level execs can pay themselves with for several years until the wheels come off and they declare bankruptcy.
Hmmmm
So, toxic (beryllium), hot and both chemically and radio active.
Still seen very little information on how you get heat out of this system.
These molten salt mixtures can be relatively well behaved if their pH is kept reasonable.
OTOH if water hits that mix things will become "interesting"
And even if it does work it's still decades from deployement.
We needs something deployable in large numbers. Now.
Wait... you want the DOE to do... WORK!? Is there any particular century or decade you'd like those results in? The world is already AWASH in studies on liquid salt reactors: Why more seat cushion fodder?
Dust off the 1950's and 60's plans, update them and BUILD ONE!
In the immortal words of Monty Python: GET ON WITH IT!
INo.
Natrium is a Sodium cooled fast reactor. It uses salt as a heat storage medium, as some solar thermal ("Power tower") designs do.
Sodium fast reactors were pushed hard by the AEC in the 60's and 70's on the basis that the demand for nuclear generated electricty (which they predicited) would exhause all of the US Uranium enegy reserves and that only the dystem with the fasted breeding cycle would save them.
Which was the Sodium fast reactor.
But 9 of the largest Uranium reserves on the planet did not come on streaam before the mid 1970's and the electricty growth never occured. They cut the raw U price 50%. Reprocessed MOX fuel is estiamted to be about 8x the cost of fuel from straight enriched Uranium (and enrichment is about 50% of the cost, and rising).
IOW their predicttion and the reason d'etre for FBR's is total BS. Which leaves you with a reactor that cannot run on natural uranium, has much higher neutron damage to the RPV, nasty errosion issues if any air get into the sodium and forms very abrassive NaO grains, and lots of trouble if any water at all leaks into the Sodium flow in the heat exchanger.
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A quick read of the article seems to show that the problems that were experienced at ORNL during the Molten Salt Reactor Experiment were mainly execution and engineering issues rather than problems with the theory. If a wire to a motor melts, that doesn't have anything to do with the reactor. If mistakes were made estimated thermal coupling to the cooling system so they could only run up to 80% of the planned output, that's another engineering problem that one hopes to catch in the R&D phase. I was never under the impression that what they had running only needed to be scaled up and duplicated a bunch of times. There were still a couple more iterations that encompassed a fuller embodiment of the total design so there was continuous processing of the core and blanket salts to remove contaminants. The article sort of misstates the usefulness of U233 in weapons. As a gamma emitter, it's too easy to detect from a distance even if it might be used. The gamma emissions are also a huge issue in trying to make a bomb with it. Any electronics could be doomed to fail.
I have yet to come across anything that would doom a LFTR design other than proper R&D and good execution of the design. I would rather not see any Sodium cooled reactors built and many fast breeder reactors sound horribly dangerous to operate since too many things can go wrong in a hurry.
"Oak Ridge National Laboratory found during the Molten Salt Reactor Experiment, fluoride salts are incredibly corrosive and required hardened materials to safely contain them."
After 9000 full power hours there was NO discernable corrosion of the hastalloy-N pipework or deterioration of the graphite core
A couple of theoretical issues (mainly revolving around Tellurium) were identified in the 1970s and the formulation tweaked
The Register 
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