Transatomic Power’s Molten Salt Nuclear Reactor | Kent Beuchert writes:
Leslie Dewan and Mark Massie, as Doctoral candidates in the nuclear department at MIT, produced a modified design of a reactor technology that first appeared many decades ago : the molten salt reactor, originally designed, built and tested at Oak Ridge Tennessee during the 1950’s 60’s and 70’s.
After her graduation, the two formed Transatomic Power in 2011, as a means of completing the design and commercializing their reactor design. Recently, they received a $2 million grant of venture capital from Founders Fund. The money will be used to test and verify the corrosion resistance of metals that their design employs in the reactor core and piping, as well as modeling the reactor design. One major purpose of the testing is to determine if the moderator’s lifespan (currently only vaguely estimated) will require periodic replacement, or will last throughout the reactor’s service lifespan. The answer to this question will not prove an obstacle to the design, only to the need for a design that provides for modulator access (for replacement).
Dewan believes one of the MSRs biggest advantage is the its ability to burn SNF (spent nuclear fuel – “nuclear wastes”) more or less completely, extracting 20 times more energy from uranium than a conventional reactor, producing a far smaller and far less radioactive final waste product, that will be much easier and cheaper to store, and will retain its radioactivity above background levels for only a few centuries rather than thousands of years. It also can be configured to burn Thorium, although that is not Dewan’s desired fuel, for several reasons : the greater perceived need to burn nuclear wastes, and the inferiority of a Thorium reactor’s proliferation safeguards, the lack of any need for an alternative to uranium fuel, as well as the current existence of a uranium fuel processing system.
The original Oak Ridge MSR design was modified in only a few ways : use of a different material for the moderator in place of the original space-consuming graphite, and slightly modifying the molten fuel salt (uranium dissolved in lithium flouride) being the most important. Together, these modifications allow for commercially competitive amounts of power to be generated, not possible from the experimental molten salt reactors built at Oak Ridge, and the ability to be powered by low level radioactive fuel, reducing proliferation concerns.
The Transatomic Power plant design has an estimated overnight build cost of $2 billion for a 520MWe unit. The lower costs are primarily due to the fact that no massive high pressure containment vessels or piping is needed for much of the plant, and also due to its higher efficiency output temps, which allow for smaller power turbines to be used. Power turbines constitute a major cost in any nuclear power plant design. With these build costs and the prospect of near zero fuel costs, there likely won’t be another power source that is cheaper, all things considered. Another advantage of the design is its ability to support load following – i.e. to alter power output quickly as demand changes. As of now only some fossil fueled and hydroelectric plants have such an ability.
This capability would allow for a larger percentage of nuclear power in any grid, which today only can exist as baseload power (although pumped storage does sometimes allow for nuclear power to be stored and then later available as hydroelectric, load following power). This plant would also likely reduce (realistically, probably eliminate) commercial prospects for the larger versions of small modular reactors, those that produce over 250 MWs. It achieves (actually, exceeds) the economies of scale of a conventional large reactor, something small modular reactors are totally incapable of. It also does not require shutdown for refueling – it is refueled at intervals and can be run continuously for decades, another cost advantage over conventional reactors.
Commercially, a $2 billion dollar 520MWe power plant can meet the needs of utilities facing only gradually increasing demand as well as those whose service area doesn’t require the 1000MW plus size of a conventional reactor, or those wanting to replace fossil-fueled load-following or baseload coal plants. Build time is estimated to be 36 months. The plant does not require any source of cooling water – the molten salt fuel liquid acts as its own coolant as it flows thru the primary loop, transmitting heat (but not radiation) to an intermediate loop. The lack of any requirement for cooling water dramatically increases the number of potential build sites. In fact, its inherent safety characteristics would allow for these reactors to be sited near large population centers, avoiding lengthy transmissions, reducing costs due to power losses and transmission line construction.
In considering the reactor’s characteristics with respect to safety, it’s hard to conceive of a situation that anyone would find threatening or dangerous. Every reactor state that one can reasonably imagine as conceivable, ends up with the reactor shutting down as the molten salt cools (slightly) and becomes a solid at which point no fission is possible (or heats up, reducing fission). No radioactive material (the molten fuel salt liquid) is ever subjected to anything other than slightly above atmospheric pressures, which essentially eliminates any radioactive blast issues, ( in fact, all pressures work towards forcing the radioactive material back into the reactor system), and no hydrogen emissions can develop to the point of posing an explosive danger.
The entire steam turbine system and its piping, which contains the only only material under significant pressure (water), is completely radiation free, meaning that any rupture in that system is, radioactivity speaking, a non-event. The fuel liquid operates at a much lower temperature than fuel rods in a conventional reactor and never contains the excessive reactivity potential possessed by a conventional reactor at the start of its two to three year run cycle.
The entire system is considered walk-away safe – no operator actions, or electricity, or pumps are ever needed in order for the system to shut down should an accident occur. The reactor will achieve a stable shutdown state in a fairly short time frame.
It’s hard to imagine anyone having any objections to this nuclear reactor design. For those attracted to the safety of Thorium reactors or concerned about future uranium fuel supplies (such as India) , this design is better all the way around. With its meager fuel requirements, uranium will be economically available from either SNF, terrestrial mining or ocean extractable uranium ( freely available to virtually every country) for many millennia, eliminating any conceivable concerns about future fuel sources. And, of course, it can burn Thorium as well, should anyone so desire.
The superior economics and flexibility and load following characteristics, lack of any need for refueling shutdown, elimination of any significant fuel cost increases, removal or reduction of nuclear waste storage requirements, a much lower build cost requirement and elimination of the economic danger of a multi-billion dollar nuclear accident, would certainly make these reactors the first choice for any grid operator. And the plants can easily be co-located with conventional nuclear plants without placing any additional water demands, and be located near the likely source of the SNF they will consume as fuel.
One finds it difficult to foresee any significant risks when buying into this reactor design, financial or otherwise. I see a real possibility for this reactor design to become not only the standard and universal nuclear reactor, but also the standard commercial power plant as well, rendering all others of this size and larger obsolete. It is everything one could reasonably ask for in a power plant.
A complete technical description, accompanied by economic and safety rationales can be found at the company’s website :
Click to access TAP_White_Paper.pdf
Am I understanding this correctly in that spent fuel assemblies currently stored at nuclear power plants could be used as a fuel in this type of reactor?
Yes, this is true
In that case, this type of reactor could solve a huge problem of nuclear waste storage since Yucca Mountain was abandoned from what I hear. (please correct me if I’m mistaken about this.) But I won’t get my hopes up too high until people with far more expertise than I weigh in on the subject.
To elaborate, the SNF would have to be processed into fluoride fuel. Roughly, the zirconium fuel rods would be cut open and the oxide fuel grains dissolved in hydrofluroic acid. Some gases are released, but they are valuable (mostly xenon and krypton) and can be stored for later use after complete decay. Some of the other fission products can be removed by solubility and volatility differences, then the actinide salts are blended with a carrier salt (mostly lithium and beryllium fluroides). The actinide salts have high melting points, but dissolve into the molten LiBeF at reasonable temps.
Any waste from this reprocessing has few actinides in it, has moderate activity, and need only be stored for a few hundred years to reach activity lower than the original uranium ore. The SNF needs to be aged for about ten years before reprocessing, but there are lots of decades-old rods in pools at every current nuke plant so there is no shortage of feedstock.
This post does read like a press release, but has no errors of fact as far as I can tell. I really do like the promise of turning what is now a liability into a valuable asset.
The French, who produce 80% of their electricity from nuclear, have a saying that there is no such thing as nuclear waste.
Robert Heinlein predicted that we’ll learn to make use of nuclear waste
Sounds like they’ve thought of everything.
It almost sounds too good to be true.
…
Sounds great. Makes a ton of sense. Therefore, I fully expect many greens and progs to be completely against it. It might make them feel yucky.
The greens will reveal themselves to be the misanthropic watermelons they are. They want YOU to starve in a cold, dark cave, not themselves. Read Plato’s Republic.
Two billion for 500MW sounds pricey to me. Is it because I’m reading a real claim instead of all the faked up green ones I usually look at?
Mark,
1 watt over 20 years produces 175 kW-hr electrical output. Thus the 500 MW would produce 8.75E10 kW-hr in 20 years. The capitol cost of 2E9 dollars amounts only to 2.3 cents per kW-hr. There would be operating costs, finance costs, and profit, but this is lower than almost any other power source, is clean and safe, and can be located near use to lower transmission losses. It looks cheap to me.
Right on the money as usual.
Now repeat the calculations with a 60 years life time as is more appropriate to a well designed fission reactor.
Such an MSR might even be competitive with the shabby “Old Nukes” we built forty years ago:
http://diggingintheclay.wordpress.com/?s=florida
The $2 billion sounds low. The main problem they will have is the unproved components. They’ll have to check individual parts. This will take time and money. I’d say they won’t start a commercial plant until 2034. If I were to buy the concept I would need $3 billion to invest and an additional $2 billion in loans. The patent and intellectual property rights could be worth a bundle if they get it done. But these ideas take a Chinese style long term outlook.
Game changer?
Extremely interesting.
This sounds like a winner and I hope they succeed.
But one correction. Nuclear plants are capable of load following and rapid power changes, anyone who disagrees just needs to look at the hundreds of naval nuclear vessels built over the last 60 years.
True most currently operating nuclear plants are not designed for load following. But that is because they were built as baseload plants and it is cheaper and more efficient to build a nuclear plant to operate at or near max capacity all the time. But with some minor changes current designs could be relatively easily built to be load following.
Interesting you brought up the Navy. Along those lines the Navy has an outstanding safety record operating reactors. I am in favor of having the military build and operate these plants. They have the expertise, they can do it on base to simplify the permitting process (military bases are everywhere), they can sell the power to utilities to fund themselves, and the sites have all the security you could want, what’s not to like.
Maybe a better option is to use a very disciplined organization? USA militarism is already a serious problem, the last thing the country needs is military personnel generating electricity.
Who would you rather trust; the military or a contractor that’s the cousin to the brother-in-law of a Congressional staffer’s girlfriend?
Perhaps the reactors are well designed and built by the private sector rather than just well operated by the Navy. Maybe we should just outlaw unions in the nuclear power industry to allow the private sector discipline comparable to the Navy. See, you can put whatever spin you like on such matters.
I agree and have thought about this a long time.
@ur momisugly ddpalmer – I was in the nuclear Navy and then the civilian industry. Civilian nukes can NOT load follow, due to their highly different design: far lower enrichment and ability to deal with different local power densities. The main cause is the about-10-hour peak to peak Xenon cycle. I will leave out the esoteric nuclear physics discussion – suffice it to say that when a plant leaves a steady-state power level, the different decay rates of different fission products create a series of (semi-manageable) power oscillations that require significant “driving” and operator attention. Making more than one power step change in a two-day period or so will set up a harmonic set of changes and make the plant hard to keep at a set power level. It won’t blow up or go over rated power levels, but will have to be lowered below an efficient level before slowly ramping back to 100%.
A different fuel construction allows the propulsion reactors to rapidly follow load. A commercial PWR uses the control rods to shape the active part of the core while power is changed by changing the boric acid dissolved in the coolant (boron is a neutron absorber with tritium being a waste product). This is a slow process as it is done by draining off some coolant and removing the boric acid with a distiller. Commercial BWR also shapes the active part of the core with the rods while power is controlled by increasing or decreasing coolant flow through the core. ( The faster the flow, the fewer voids in the core so you get more moderation and higher power.) The BWRs were advertised as able to follow the load rapidly, but there seems to be a problem with rapid load changes. Both types have zirconium rods with ceramic uranium oxode fuel pellrts shaped like miniature “cans”. Rapid changes in power levels seemed to cause differential expansion in the rods which would lead to fuel perforations and increased fission products in the coolant. At least that was the theory of the Reactor Engineer at the plant where I did an operator traing class back in the 70s. It may have changed.
Naval propulsion reactors don’t work that way.
Regards
Steamboat Jack (Jon Jewett’s evil twin)
Who was the maroon that said that giving humanity access to cheap, clean, reliable power was akin to handing a toddler a loaded gun?
Until you can stamp that mindset out from society, nothing will ever be good enough.
As Paul
Ehrlich put it, “Giving society cheap abundant energy is . . .
like giving an idiot child a machine gun.”
Don’t dismiss Paul Ehrlich.
He may have an insight into the mind of an idiot child.
Ehrlich has been proven wrong on so many things. Why do we still quote this buffoon?
@ur momisugly Jim Brock –
Your words are an affront to buffoons everywhere.
Paul Ehrlich, different words but same meaning.
Yes, I had intended to mention that I was paraphrasing.
Please read “Plentiful Power” by Charles E. Till and Yooh Il Chang. It discusses the history behind this. Also read this: http://www.scientificamerican.com/article/smarter-use-of-nuclear-waste/.
I have been waiting for this for some time. This is good stuff. Thanks.
Not behind this particular technology, but another with the same benefits (the IFR sodium cooled fast reactor). GE-Hitachi has ready that technology maybe since 20 years, now, it’s called PRISM:
http://gehitachiprism.com
I don’t have anything against nuclear, but the hard-sell language in the article is putting my back up. But wait! There’s more… If it sounds too good to be true, it probably isn’t.
I suppose we’ll know if just 1 plant is built. Countries around the world can then see it in operation etc and decide whether it’s worth buying. A pilot if you like. If it does what it says on the box then Greenpeace should promote it seeing they are always complaining about nuclear waste.
They are not offering to sell you one. Relax.
MSR == Molten Salt Reactor.
“Low level radioactive fuel” What’s that? It certainly can’t be “low level radioactive waste”, as that include labcoats. There’s no reference to that in the .pdf. Also, no reference to “modulator access” – likely should be moderator.
“it’s hard to conceive of a situation that anyone would find threatening or dangerous.”
You’ve never met the Clamshell Alliance in NH.
There are plenty of people conditioned to panic over radioactive stuff like bananas or coal.
“…as that include labcoats.”
With or without person inside?
🙂
Rick: where did you see the “low level radioactive fuel” quote? It may be a valid statement. “LLR Fuel” would be different than LLR Waste. You probably know it, but the use of the term low-level has been a poor misnomer. LLR Waste (the better percentage being CO-60) can have very high activity levels. If they are using applying the term “low-level” to fuel, I suspect they mean low enrichment. If this is the application, it is a confusing term to mean low enrichment. I was flabbergasted that they can use as low as 1.8% U-235 enrichment. That would be a huge cost savings in enriching Uranium, plus the reduction in proliferation security issues.
PS: I loved the “with or without persons in the lab coats” comment. I can think of a few whom I wouldn’t mind being used as fuel. : ) But let us not give the government any updated, technologically improved ideas for solyent green.
4th paragraph of the main post:
The original Oak Ridge MSR design was modified in only a few ways : use of a different material for the moderator in place of the original space-consuming graphite, and slightly modifying the molten fuel salt (uranium dissolved in lithium flouride) being the most important. Together, these modifications allow for commercially competitive amounts of power to be generated, not possible from the experimental molten salt reactors built at Oak Ridge, and the ability to be powered by low level radioactive fuel, reducing proliferation concerns.
When I fly, I need to skip eating bananas for a while to get my radiation levels back to normal. I’m never quite sure how many though, what with altitude, duration and so on. If I inquire at the counter, they will look at me funny and I end up having to go through additional security to board.
Corrosion is their problem to be solved. Finding a moderator containment material that is both corrosion resistant and radioactive resistant in this salt bath may not be easy.
Tantalum is likely to do the trick, but of course it will be ruled against because of “blood Coltan” which never amounted to more than a couple of hundred kilos now and again. Modern barbarians are waiting out there to pounce on such an idea!!.
This makes too much sense. The eco-jihadists will have to oppose it on point of principle, as they want all of the world subservient to them. Cheap clean energy for the masses? Utter heresy!
If Tom Steyer was actually interested in something other than buying controlling interest in the White House he’d be all over this.
“It’s hard to imagine anyone having any objections to this nuclear reactor design.“.
There are some people of whom it’s hard to imagine anything nuclear that they would not have objections to.
That’s exactly what I was going to say.
I was about to say the same thing.
very interesting, would like to see more studies done and testing.
If it sounds like a great idea, the greens will hate it. Unless it ends up with us living in mud huts, it is not enough.
You misunderstand the objective of the greens, they hate the fact that you are alive. You are correct though, for them it’s never enough.
If something sound too good to be true …
This whole article sounds too much like a door to door sales pitch.
Where are the negatives?
There are always negatives. But is this case all very manageable. Check out the link I point to above and the book if great too. Liquid thorium reactor are also good but I think this does one better. We could have both. They both solve the waste issue. This is nothing new, just in the background.
No Cooling water? The Rankine cycle is the fundamental operating cycle of all power plants where an operating fluid is continuously evaporated and condensed. http://www.thermopedia.com/content/1072/
They may not need water in the salt-loop, PB reactors do not either, but they will have no efficiency in the turbine feed loop with out it.
Yep. To say “no cooling water” cause a credibility gap a mile wide. Someone has overlooked the operating principles of turbo-generators..
Yes, but with the pressurized water on a separate loop from the radioactive salt, wouldn’t that eliminate most of the risk that current reactors have with radiation leaks?
They are almost certainly referring to emergency cooling systems. No elaborate plumbing is needed to cool a reactor core after shutdown.
“It’s hard to imagine anyone having any objections to this nuclear reactor design….”.
Although I am fully supportive of MSR nuclear power (whether thorium or uranium fuelled) myself, there is a hardcore anti-nuclear movement out there who will never accept the idea of peaceful civilian nuclear power no matter how safe the technology is or how you try to convince them that it is.
Cue Roger Sowell in 3….2….1….
Roger will be here soon I am sure…..
That $2 billion is around 4 (or 5) times the cost of a fossil fuel plant and a lot lower than a conventional nuclear one. But annual fuel costs (or lack there of) should make it about as cost effective (maybe even better) as a fossil fuel plant in a few years.
Current PWRs can do load follow, if so designed.
The article also seems to imply that no cooling water is needed. The vast majority of cooling water at any NPS is for the turbine condensers; very little water is required to cool the nuclear plant.
You are correct, the plant would still need cooling for the steam cycle. However, you can use air cooled condensers, if you are willing to take the efficiency hit.
While I love the idea of a MSR, there are things that must be guarded against. For one, the fuel. IF they are to use SNF, then it needs to be processed. And stored / recovered. And shipped. Remember that in Fukushima, it was a SNF pool that overheated and caused “issues”….
Then there is that metal wall between the very hot molten salt and the very wet water… That needs to NOT suffer significant erosion over years (decades?) of high speed high temp flow of both salt and water. Not a walk in the park.
I’m all for building these things (and using Thorium, SNF, whatever…) in them. But to pitch them as super easy and super safe and tasty as chocolate just smacks of hype… It will be a hard engineering job and they WILL find “issues”. Just hopefully an order of magnetude or so smaller than with BWR / PWR / etc.
(Oh, and the slight slam on Thorium is wasted breath too. It is not a panacea, but no more difficult to use as fuel than U. CANDU reactors can run it now and it can be put in fuel bundles in our existing fleet of PWR / BWR / etc. too. Yes, you need to think about the change of operating mode / pace. So? It’s just an economic thing really to choose U over Th, and both will last for 10s of thousands of years… so no hurry.)
On ship reactors as load following: Yes, but they use a 20% or so enriched metal plate fuel in many of them (especially smaller submarine designs). That means enrichment… which means nuclear weapons fuel is just a question of ‘how long to run the enrichment’… THAT is why we don’t have them for power reactors. They are on the forbidden path that lets you make SNM “boom stuff’. It is possible to make a load follower without that approach, but it is bigger and slower to change state.
Well yeah they are learning to advertise. Thorium is more abundant than many think. It is a nuisance waste product in rare-earth deposits, some of which have more thorium than rare earths. Beach sands in many parts of the world have an abundance of it and these are processed for titanium, zirconium and abrasive garnet (especially India and Australia) Often there is a bit of U in the ore, too – probably not a problem used as a fuel. In processing of rare earth ores, thorium is removed early as an insoluble compound. The present economics legislate against high Th ores simply because of having to dispose of them in an acceptable way. Such a reactor would be a boon to the rare earth production industry.
As a graduating senior in ChE (1952) I was told that I could get a job working on this molten salt reactor if I wanted it. Apparently there have been some insurmountable obstacles or it would be working right now.
Kill by Clinton, John Kerry in 1994.
After 42years with no progress?
Good call.
It worked. Killed by Pentagon – no weapons grade by product. See last paragraph:
http://energyfromthorium.com/2012/06/15/1973-news-article/
Ah, well there was a (Cold) War on.
And that was in the days of Nixon, not Clinton.
But if it does work then all power [to their] elbow.
(For me, the sales pitch was too much. It sounded too good to be true so I was instantly cynical).
I agree with you M Courtney, It read more like an investor sales pitch than an operational analysis.
The bulk of the early work on these designs focused on component lifetime – specifically, developing alloys able to maintain their mechanical and material integrity in a corrosive, radioactive salt environment. Experimental tests running over several years at ORNL in the 1960s and 1970s showed that modified Hastelloy-N possesses the necessary chemical and radiation stability for long-term use in molten salt reactors. Despite this progress, the USA remained focused on light-water reactors for commercial use, primarily because of extensive previous operating experience with naval water-cooled reactors and early commercial power reactors. Advocates of thorium and increasing demand for small modular reactors drove renewed examination of molten salt in the 1990s. In 2002, the multinational Generation IV International Forum (GIF) reviewed approximately one hundred of the latest reactor concepts and selected molten salt reactors as one of the six advanced reactor types most likely to shape the future of nuclear energy “due to advances in sustainability, economics, safety, reliability and proliferation-resistance” [2]. From the white paper, quote unquote.
the ‘insurmountable obstacles’ have been the lobbying efforts of the conventional enriched uranium suppliers, who have fought for decades to keep any research money from going into thorium. They greatly reduced and then killed the thorium projects we had going in the 1950s and 60s. Why? Because the uranium nuclear industry makes its money not in building plants, but in selling expensive fuels. Thorium fuel is inherently cheap, and requires no expensive refining. So they can’t make money on it. Their efforts have been so successful that the only way our government has been able to get research going is through a joint project with the Chinese, who have provided most of the funding, while we have provided most of the scientific expertise.
fhhaynie
August 27, 2014 at 7:09 am
“Corrosion is their problem to be solved. Finding a moderator containment material that is both corrosion resistant and radioactive resistant in this salt bath may not be easy.”
I agree. That’s why it is important to get one of these molten salt reactors up and running as a demonstration plant, in a safe location. Run it 30 years and then shut it down and decommission it. Then we’ll know if it is a practical technology or not. Area 51 would be a good place to start.
The Russian BR-5 fast reactor ran from 1959-2005, 43 years. Does that help?
5MW is a lot smaller than 500MW
Corrosion/erosion properties are generally immune to scaling effects. Unless there are significant changes in fluid velocity or temperature during scale up, a 43 history at 5MW tells you all you need to know for 500MW.
Some thoughts:
– $2B for 500MW is pretty competitive relative to current LWR (light water reactor) prices (~$4B – $6B for 1000MW, conservative guess).
– Eliminating the need for cooling water is HUGE, but I struggle to understand how this reactor accomplishes it. From the above provided description (as well as other literature I’ve read on this), it’s not clear how the heat exchange between the salt and the secondary side coolant (water) leaves the salt any cooler than the primary side water in today’s reactors. This is currently achieved through cooling water (e.g. lake, river, ocean) that pulls a significant amount of the remaining heat out of the secondary side after passing through the turbine.. This allows the secondary side to extract the most heat possible from the primary side. How is it achieved in this reactor?
– Reactor sites today have incredibly strict seismic requirements. It seems likely that this reactor would have to follow the same.
– Proliferation concerns with thorium fuel are pretty minimal. If I understand it correctly, there’s roughly the same level of effort required to enrich by-product of thorium into weaponized material as is required to enrich plutonium pulled out of the ground. Effectively, a net-zero proliferation impact.
– Super long continuous run-times seem to me to be “pie-in-the-sky” marketing. The 2nd law’s still in effect. Maintenance is still required, even if refueling isn’t. Still, this doesn’t reduce the interest of this reactor. It’s just that we’d have to be realistic about maintenance and upkeep.
– To answer the above question, yes, this reactor is claiming to use the spent nuclear fuel (pellets) currently contained in the fuel assy’s at commercial nuclear plants.
– Current nuclear reactors can load-follow, just not the ones in the US. The designs have to be modified and beefed up to withstand the transients (among other things). France’s reactors are load-following.
– I think a major reason that molten salt was not pursued was the extreme corrosiveness of it. Maybe current material technology has solved this. Also, I think there’s an “industrial” risk (non-nuclear) of the salt reacting (chemically speaking) with the secondary side water. Heat exchangers leak. Inevitably (it seems). I’m curious how this concern has been addressed.
That’s all for now…
rip
Probably should have refreshed before posting the comment…sorry for being repetitive.
rip
Heh. I managed to misspell fluoro- twice, in different ways. Annoying word, that.
Their mention of a conventional water-based rankine cycle is a bit odd- almost all the other discussion of MSRs focuses on brayton cycles which can run at higher temps and achieve higher carnot efficiency. That also eliminates the salt-to-water heat exchanger, replacing it with a salt-to-helium HX, much safer.