Sciencemadness Discussion Board

Chemical hazards of liquid thorium fuel reactors (LFTR)

watson.fawkes - 23-9-2012 at 10:00

I got into a discussion this last week with a zealot for liquid thorium fuel reactors, who promoted them, roughly, as The Absolutely Best Design For Nuclear Power Ever. You've met the type, I'm sure. In particular was the claim that "they absolutely could never melt down". Well, I'm suspicious of any such category of claim, and in the wake of that conversation decided to do a little digging. The upshot is that they seem to have been fighting the last war, that is, these designs don't undergo meltdown because the don't use ceramic fuel that can melt. So I got to wondering about whatever the analogue of meltdown would be for this reactor.

Here are a few relevant Wikipedia articles on the subject:
Liquid fluoride thorium reactor
Molten salt reactor, which has some technical details about LFTR that aren't in its own article.
Alvin M. Weinberg for some of the history. He was the administrator at Oak Ridge that promoted the original development of the technology.
Thorium fuel cycle, for why you may need mix some uranium into your thorium fuel.
FLiBe, the basic salt mixture, with melting point 459 °C.

All these technologies seem to use fluoride salts. The central composition seems to be 2 LiF + BeF2, which looks like it's a low-melting eutectic. This mixture is used both as a fuel carrier as well as a secondary coolant. The fuels are ThF4 and UF4 dissolved into the basic salt mixture. ZrF4 was in the fuel mixture at the ORNL prototype; I don't know why. Operational temperatures are around 650 ° - 700°C. There is evidently a negative temperature coefficient of reactivity somehow; I haven't tracked down why. This is one of the "inherently safe" features touted for the design.

Now I don't know a whole lot of fluorine chemistry, but it seems that there's a whole lot of things that could go wrong here. Fluorine is just really damn reactive, and I can't imagine that there aren't fluorine-transfer reactions that are as exothermic as thermite-like oxygen-transfer reactions. One piece of anecdotal support for this is the use of PTFE as an oxidizer. And since I don't know a lot about fluorine, I welcome the input of people who do.

So, as a case study, consider what happens when one of these molten salt mixtures hits concrete. The very first thing that happens when anything sufficiently hot hits concrete is that its adsorbed and chemically-bound water flashes off into steam. I'd have to guess that you may well get the following phase-driven reactions, even though they're endothermic, since the HF comes off as vapor and the oxides as fine powders:
  H2O + 2 LiF --> Li2O + 2 HF
  H2O + BeF2 --> BeO + 2 HF
If this happens, you've lost much of your cooling capacity for the nuclear reaction. Then you've got the oxides in Portland cement to consider. I don't know if the following reactions are exothermic or not.
  2 CaO + ThF4 --> 2 CaF2 + ThO2
  SiO2 + ThF4 --> SiF4 + ThO2
Silicon tetrafluoride is very volatile, almost as much as silane, so the second reaction could be phase-driven. It's also formed by the attack of HF on silicates, which provides a further phase driver to the Li and Be reactions above. Now thorium oxide is quite refractory and doesn't melt down readily. But these reactions, if they can happen, show the possibility of a meltdown scenario that's just one extra failure separated from the ceramic fuel case.

So one question I have is whether these salt mixtures are at some kind of thermodynamic minimum, so even if the reactions above occur, that the reverse reactions will reestablish the salt mixture. If they do, then there's much less to worry about. SiF4, though, seems like it might be a real issue, since it's unlikely to rapidly make its way back on its own. And if you get precipitation of thorium oxide, then you've lost the negative coefficient effect.

So. Is the above scenario even partly accurate? What else might happen? I'd hope the engineers leave out structural aluminum entirely, as if it's activated as a reducer for the fuels you've lowered the meltdown temperature a lot, as well as providing a chemical heat source. I'm sure my imagination is still rather limited about possible sources of problem.

Endimion17 - 23-9-2012 at 11:19

It's a proven fact those reactors suffer from corrosion. There's no "absolutely safe" nuclear reactor available. It can't go into a typical nuclear meltdown with classical corium digging through concrete and all that stuff, but radioisotope breaches and subsequent contamination of the reactor building are a possibility.
Thorium technology is a great potential, it really is, but its vehement proponents are crackpot-like dumbasses that never look at the big picture. They're prone to conspiracy theories. So, yes, I know the "type" very well.

blogfast25 - 23-9-2012 at 12:53

I know next to nothing about these reactors but you’re right about these four reactions apart from the third one which is probably endothermic and not phase driven.

Don’t tell me someone is planning to put one of these in an aircraft, right?

watson.fawkes - 23-9-2012 at 20:47

Quote: Originally posted by blogfast25  
Don’t tell me someone is planning to put one of these in an aircraft, right?
From the above Wikipedia page on Alvin Weinberg:
Quote:
ORNL successfully built and operated a prototype of an aircraft reactor powerplant by creating the world's first molten salt fueled and cooled reactor called the ARE (Aircraft Reactor Experiment) in 1954, which set a record high temperature of operation of ~815 °C (1,500 °F – red heat)). Because of the radiation hazard to the aircraft crews and the subsequent development of ballistic missiles, mid-air refueling, and longer range jet-fuel bombers, President Kennedy killed the military's Aircraft Nuclear Propulsion (ANP) program in June 1961. This allowed ORNL to shift its focus to a civilian version of the meltdown-proof Molten Salt Reactor (MSR) from the military's "daft" idea of nuclear powered aircraft.
As to your question, it's your call.

watson.fawkes - 23-9-2012 at 20:57

Quote: Originally posted by Endimion17  
It can't go into a typical nuclear meltdown with classical corium digging through concrete and all that stuff
And yet that's exactly what I'm concerned might be possible. Now it won't happen because the core loses moderation, as with ceramic fuels. But suppose the core lost containment because of mechanical failure: earthquake, missile strike, sabotage, etc. If the secondary containment is concrete, my original suggests that it's worth testing to ensure that the chemical reactions don't lead to a ceramic core developing in the puddle. If the secondary containment is steel or some predominantly ferrous alloy, it seems you'd get fluorine transfer to the iron from the least reaction anion in the salt mixture, which would be Th and/or U, which would then drop out of solution, and we're back to making a core in the puddle again. Reminder: these cores-in-puddles have no moderator and can quickly reach criticality.

I will freely admit that these are less likely scenarios and an improvement over previous designs. Yet "impossible" to melt down seems like either (1) a lie, or (2) disregard for possibility so flagrant that it becomes tantamount to a lie. It's true that the can't melt down in the fashion that previous reactors melted down. Instead, it seems they may be able to melt down in their own particular way.

Endimion17 - 24-9-2012 at 03:52

Quote: Originally posted by watson.fawkes  
And yet that's exactly what I'm concerned might be possible. Now it won't happen because the core loses moderation, as with ceramic fuels. But suppose the core lost containment because of mechanical failure: earthquake, missile strike, sabotage, etc. If the secondary containment is concrete, my original suggests that it's worth testing to ensure that the chemical reactions don't lead to a ceramic core developing in the puddle. If the secondary containment is steel or some predominantly ferrous alloy, it seems you'd get fluorine transfer to the iron from the least reaction anion in the salt mixture, which would be Th and/or U, which would then drop out of solution, and we're back to making a core in the puddle again. Reminder: these cores-in-puddles have no moderator and can quickly reach criticality.

I will freely admit that these are less likely scenarios and an improvement over previous designs. Yet "impossible" to melt down seems like either (1) a lie, or (2) disregard for possibility so flagrant that it becomes tantamount to a lie. It's true that the can't melt down in the fashion that previous reactors melted down. Instead, it seems they may be able to melt down in their own particular way.


I don't know, I'd really have to sit down and think about all this to give my honest opinion, but I'd like to comment on something I'm well aware of - the typical meltdowns. I wouldn't like people to learn incorrect info.

The worst one ever was in Chernobyl's reactor #4 and even there, where actual fuel-concrete lava ("corium") was made, criticality wasn't responsible for digging through, to the basement floors.
Thing is - literal meltdowns, where corium collects in a puddle and generates so much heat that it digs a hole through a powerplant, is next to impossible. Chernobyl corium dug through like one or two concrete floors because it was already extremely hot when it fell out from the reactor. There wasn't any noteworthy criticality on a large scale.
When corium hits the concrete, tremendous amount of heat is pushing out water from it. As the hole is made, corium is being left behind. It's like a lava, viscous and sticks to concrete walls of the hole. Therefore it will be spent, dissipated along the way. That's exactly what happened in Chernobyl. Almost all of the core fell into the basement (tonnes of nuclear material!), but it didn't coalesce into a puddle ready to dig down. That's why those cases where corium digs through a power plant and hits the water table are virtually impossible.

At TMI, corium stopped forming in the reactor vessel itself. It did make a puddle at the bottom of the vessel and there was a blob in the center of the disrupted rod geometry, there had to be local criticality, but it isn't self sustaining. It stops.
The reason meltdowns are a nightmare is not because of demonic, almost sentient and evil digging, but because it's a tremendous expense of money, and the volatile radioisotopes of iodine, caesium and strontium escape the vessel. We all know how tiny atoms and molecules are, and we're well aware of Avogadro's constant. Add violent ionizing radiation levels into the equation and you get highly dangerous scenarios from even small vessel breaches.

That's why I think LFTR can't do much damage, either. Also, remember that the boiling point of FLiBe is less than 1500 °C, compared to the boiling point of corium which could be close to 4000 °C, as it's similar to other refractory materials. Such temperatures don't occur in meltdowns.
So any large heat excursions in LFTR would cause it to boil away, therefore extinguishing the criticality which is tough to accomplish there.

However when we're talking about chemical reactions, facts are - reactants are spent. I really don't see any large threat here.

You also have to remember that even today's modern reactors built in France (it's like the only smart country in the world when it comes to energy) have built-in corium pools that let the material flow in a pancake form, rather in large drops like in Chernobyl (infamous "elephant foot"). I'm sure LFTRs would employ it, too. Those reactors are old, and you can be sure that, decades later, new security systems would be employed.

Sleep tight, dear Watson :D, the future is safer uranium/MOX nuclear fission, unless the world succumbs to morons like in Japan, that's turning to large imports of coal and oil because they're freaked out by (relatively) negligible vintage plant failures when doused with a 10m tsunami and a doomsday earthquake.

[Edited on 24-9-2012 by Endimion17]

blogfast25 - 24-9-2012 at 05:28

Are we sure Th and U fluorides are reducible by iron? Personally I think these equilibria lay close to the U, Th fluorides, not the iron (III?) fluoride.

[Edit:

For UF4 +4/3 Fe === > U + 4/3 FeF3

I get a Standard Reaction Enthalpy of about + 500 kJ/mol, based on NIST/Wolfram HoFs), so unless the FeF3 blows off (unlikely, it's highly ionic) this reaction does not proceed. These high period ionic fluorides have very high HoFs...]

As regards 'freaking out' (Japan), that really happened even more in Germany, a country not precisely earthquake or tsunami prone.

In my book current civil nuclear technology (energy) should be a 40 year stop gap until something better is developed.

[Edited on 24-9-2012 by blogfast25]

Endimion17 - 24-9-2012 at 06:22

Quote: Originally posted by blogfast25  
As regards 'freaking out' (Japan), that really happened even more in Germany, a country not precisely earthquake or tsunami prone.

In my book current civil nuclear technology (energy) should be a 40 year stop gap until something better is developed.

[Edited on 24-9-2012 by blogfast25]


40 years?! Why???

That's because Germany is being run by stupid dickheads. The only thing they're going to elevate is CO2 output and electricity bills. Oh, and France's income.

They've succumbed to fear of fission because of freak incidents (one due to communist party negligence, other due to a doomsday event that went along with ease), and because their old generation power plants are slowly giving way because the fucks were too stupid to invest into new ones. No wonder things are crumbling. They're old and need to be replaced.
Second generation power plants are history we should finally lay to rest. France is developing fourth generation already, and the rest of the Europe is all mushy about the very concept of fission.
I've seen the new designs. They're just fantastic. Personally, I think we've close to breaching the upper limit where increasing the active and passive security is just for the sake of someone's profit. Nothing is being accomplished if the factors of strength are elevated to sky high values.

India is pushing LFTR. They're actually developing it, just as France has developed PWR. It's about progress and simple environmental facts. We need energy, and we can't continue to burn unsightly amounts of fossil fuels anymore, and classic renewables are simply not enough, or contain hidden loopholes that fuck up the environment even more. This bacterial growth of our virus-like behaviour has to stop.

It's amazing how France is even recycling their spent fuel, thus extracting more and more energy from the same batch of fuel.
Being independent in the terms of energy is a blessing. So far, France was collecting money from Italy which is run by cowards and mafia, and now it will add Germany. One day I just might move there, who knows? I'd just have to learn French.

[Edited on 24-9-2012 by Endimion17]

watson.fawkes - 24-9-2012 at 06:39

Quote: Originally posted by blogfast25  
For UF4 +4/3 Fe === > U + 4/3 FeF3

I get a Standard Reaction Enthalpy of about + 500 kJ/mol, based on NIST/Wolfram HoFs), so unless the FeF3 blows off (unlikely, it's highly ionic) this reaction does not proceed. These high period ionic fluorides have very high HoFs...]
Thanks. I hadn't looked up the reaction before my brief response. It's useful to know that ordinary steel might work for secondary containment, since it's a well-understood material.

hyfalcon - 24-9-2012 at 07:03

Quote: Originally posted by watson.fawkes  
Quote: Originally posted by blogfast25  
Don’t tell me someone is planning to put one of these in an aircraft, right?
From the above Wikipedia page on Alvin Weinberg:
Quote:
ORNL successfully built and operated a prototype of an aircraft reactor powerplant by creating the world's first molten salt fueled and cooled reactor called the ARE (Aircraft Reactor Experiment) in 1954, which set a record high temperature of operation of ~815 °C (1,500 °F – red heat)). Because of the radiation hazard to the aircraft crews and the subsequent development of ballistic missiles, mid-air refueling, and longer range jet-fuel bombers, President Kennedy killed the military's Aircraft Nuclear Propulsion (ANP) program in June 1961. This allowed ORNL to shift its focus to a civilian version of the meltdown-proof Molten Salt Reactor (MSR) from the military's "daft" idea of nuclear powered aircraft.
As to your question, it's your call.


My father worked on this project. I've heard first hand stories about this.

blogfast25 - 24-9-2012 at 07:08

Watson:

From one of your links:

”The MSRE was located at ORNL. Its piping, core vat and structural components were made from Hastelloy-N and its moderator was pyrolytic graphite. It went critical in 1965 and ran for four years.”

And elsewhere in your links (can’t find it just now) in the discussion of results it says that the Hastelloy held up very well, bar a minor problem with a tellurium isotope, which was rectified with addition of niobium.

Iron really doesn’t seem to be an issue.

And the reasons for choosing fluorides (with their own disadvantages of cost, toxicity and other dangers) is clear. Chlorides would have lots of advantages but just wouldn't do in other ways.

Endimion: careful you don't start sounding like the zealot you were (rightly) attacking! ;-) It may be a plattitude but nuclear does have some serious issues, IMHO. Said as someone who is 'reasonably pro'...

[Edited on 24-9-2012 by blogfast25]

watson.fawkes - 24-9-2012 at 07:20

I am not assuaged, indeed, rather the opposite.
Quote: Originally posted by Endimion17  
I'd like to comment on something I'm well aware of - the typical meltdowns
[...]
That's why I think LFTR can't do much damage, either. [...] So any large heat excursions in LFTR would cause it to boil away, therefore extinguishing the criticality which is tough to accomplish there.
[...]
Sleep tight, dear Watson :D, the future is safer uranium/MOX nuclear fission [...]
Please do understand that I'm not angry, either at you specifically or in general about this. Yet I find this style of reasoning not only unpersuasive, but fallacious. The rhetorical sequence is basically this: "Because the reactor does not fail in a way we already know about from the past, it will not fail in the future."

I'm not against nuclear power, but I am against irresponsibility and denial that has characterized the nuclear industry since its origins in national security circle under cloak of secrecy. The anti-nuclear movements in Japan and Germany are acting against a social-technological nexus of nuclear technology and the people who promote it, not against the technology itself in isolation. This is a point that advocates of nuclear energy seem not to be aware of, that the historically awful behavior of much of the nuclear industry is much more the problem that any risks of the technology itself.

My exhortation, therefore, is to stop arguing in the traditional fashion, because it's damaging to your own cause. You should know, because I doubt you said this with any intent to offend, that I find hearing you telling me to "sleep tight" is offensive. Here's a summary of what I hear: "Shut up. Stop thinking. We'll take care of it." And when I hear similar things from bad actors such as GE, I also hear this: "Fuck you if you try to interfere with our profits." (Insofar as I know, you don't work in the nuclear industry, so I am not claiming this part applies to you.) Stephen Fry has a great attitude about offense taken in response to artistic expression: "So what?" This kind of offense taken against the nuclear industry, however, has political consequences in democratic societies. And those political consequences have already manifested themselves in Japan and Germany.

As to the specific technical argument, you're saying that the reactor liquid would boil away, extinguishing any chance at criticality, which I would agree with if we were certain that this is what would happen, but which we are not certain of. In a pure evaporation scenario, you've made the argument (implicitly) that the solute will dissipate with evaporating solvent. This may not always be true. The boiling point of FLiBe is 1430 °C. The boiling point of ThF4 is 1680 °C. If the FLiBe eutectic boils off separately from the ThF4 (which I don't know one way or the other), then there's a temperature range where solvent evaporation leads to fuel concentration. Therefore, until we have experimental data on what happens when the liquid fuel-solvent mixture boils, it's improper to argue on grounds of plausibility that there's no risk here.

But there's another way in which it seems you've misconstrued my original argument. The argument I made in my first post is that there's a plausible scenario where the solvent FLiBe does not evaporate away, but rather reacts away, leaving the solute, which contain all the fuel nuclides alone, with neither moderator nor coolant. This can happen simply at the liquid operating temperature, which is a few hundred degrees below its boiling point. The temperature rise from criticality of concentrated solute would happen, in this scenario, after the solvent is already gone.

Endimion17 - 24-9-2012 at 08:27

Quote: Originally posted by blogfast25  
Endimion: careful you don't start sounding like the zealot you were (rightly) attacking! ;-) It may be a plattitude but nuclear does have some serious issues, IMHO. Said as someone who is 'reasonably pro'...

[Edited on 24-9-2012 by blogfast25]


I don't want to come as a "110%" unconditional, absolute supporter of uranium/MOX fission. I'm well aware it's not the final solution (even breeders aren't forever though they're the second, quite longterm step) and it's not the current "Solution".
But I do stand heavily opposed to the quasi-green fascism that is fueled by people's fear and ignorance, that's extinguishing every single fucking NPP in one country. That's insane. Ask the French do they like their cheap electricity, and the income they partially spend on ever repeating circle of improving the existing technology.

Take USA for an example. Even since TMI, the progress virtually ceased. The power plants age, and you can't fix them forever. Even the reactor vessels age just because of neutron bombardment and become more and more brittle.
But instead of making better plants with even greater safety, USA lets their reactors age and then when something stops working, it's "nuclear fission is BAD" all over the media. Well where the hell is logic in that?
You can't rely on 40 year old reactors to power up a 21st century needs. Personally, I'm way more afraid shit is going to happen in USA, than I'm afraid something is going to happen in France, which is in my relative neighbourhood.
Quote: Originally posted by watson.fawkes  
Please do understand that I'm not angry, either at you specifically or in general about this. Yet I find this style of reasoning not only unpersuasive, but fallacious. The rhetorical sequence is basically this: "Because the reactor does not fail in a way we already know about from the past, it will not fail in the future."


I think you misunderstood what I wanted to say. Of course they can fail, but with progress, comes the ever diminishing chance something can go wrong. And even if it goes wrong, the chances are slim it will go wrong in the most dreadful way imaginable, and that's Fukushima 1. What happened there were meltdowns and hydrogen burps, and some volatiles lost.
Chernobyl can't be compared because that unit was different, obsolete and had no containment. Fukushima 1 scenario is a worst case scenario that happens when every outer safety system fails, and it failed because there was a huge fucking wall of water that stripped away the entire eastern coast. Everyone was so obsessed with that powerplant, like there weren't almost 16 thousand dead people and whole cities wiped out. I mean, come on, what are the priorities here?

Nuclear reactors will fail in the future. Chances are, the ones that fail will be the oldest with bandaids on pipes. You know, the commercial ones in USA, run by Mr. Burns. ;)
Facts are LFTR aren't fail-proof. They can fail, too, despite what the loony fans think.
That's why safety mechanisms exist. Containment units. There are proponents of LFTR that say containment is unneccessary. I say "Fuck 'em, build the unit."
Build new generation reactors in safe zones not prone to earthquakes and tsunamis, that's it.
Quote:
I'm not against nuclear power, but I am against irresponsibility and denial that has characterized the nuclear industry since its origins in national security circle under cloak of secrecy. The anti-nuclear movements in Japan and Germany are acting against a social-technological nexus of nuclear technology and the people who promote it, not against the technology itself in isolation. This is a point that advocates of nuclear energy seem not to be aware of, that the historically awful behavior of much of the nuclear industry is much more the problem that any risks of the technology itself.


Sorry, but you're kind of demonizing the whole industry just because some parts of the world have a dirty history.
Civil nuclear industry is a completely different thing compared to military industry that's inherently ill and self destructive. Most of the power plants in the world have nothing to do with that sector. Some are government operated, some are commercial, but the age of military involvement is over in more civilized parts of the world.
We've left behind the modus operandi that we're seeing now in Iran. (and quite possibly Israel, but they are like protected species so let's not poke into that)

My country owns one PWR nuclear reactor (actually half, on the other side of a neighbour country's border) and it has nothing to do with the military. It was involved, during the socialism when it was built. It was almost a top secret project, but that time has passed. The dumbasses from the military (which is like 99% of it) thought it could be useful for making weapons, so the scientists and engineers got lots of money. So they've built a cool PWR civil power plant that can't be used for making atomic weapons and making other countries think we're awesome. Soon the socialism crumbled and the power plant was left behind, forgotten by the crumbling military that was busy with slaughtering people.
Now it's a place everyone can visit and a place where people can go and study. It's puffing out water vapor and megawatthours. Every time the refueling procedure starts, the media screams about it (IT'S BEING SHUT DOWN!!!1) and creates panic. And we get along. I suppose that's the only nuclear power plant we'll be operating in a long time. When it shuts down in 20 years or so, we're basically screwed because we barely have the money for basic stuff. It's back to coal for us.

Maybe it's different in USA, I don't know. I'm just describing what's happening in most of the Europe that is satisfied with their plants.
Quote:
My exhortation, therefore, is to stop arguing in the traditional fashion, because it's damaging to your own cause. You should know, because I doubt you said this with any intent to offend, that I find hearing you telling me to "sleep tight" is offensive. Here's a summary of what I hear: "Shut up. Stop thinking. We'll take care of it." And when I hear similar things from bad actors such as GE, I also hear this: "Fuck you if you try to interfere with our profits." (Insofar as I know, you don't work in the nuclear industry, so I am not claiming this part applies to you.) Stephen Fry has a great attitude about offense taken in response to artistic expression: "So what?" This kind of offense taken against the nuclear industry, however, has political consequences in democratic societies. And those political consequences have already manifested themselves in Japan and Germany.


I don't know what's the status with Japan because most of the info we get is anime-bukkake-tentacles-samurai bullshit.
But I know what's up with Germany. There's no "Shut up. Stop thinking. We'll take care of it."
That might be an issue in USA, but not here. It might be tough for you to accept it, but the situation there really is very different. I am a kind of liberal, I'm truly all for human rights, I'm disgusted by the hypocrisy of the West, but I'm appaled by the rotten state of this self destructive liberalism coupled with recycled mush of failed ideologies that's etching European countries. That's just another name for "usual bullshit" used for making some groups of people rich. That's all there is. That's all there ever was. Money. You can squeeze money from just about anything, including "concern for our children's safety".

Thing is, nuclear industry needs to be controlled. Heavily. It's run by people, and people tend to lie and fuck things up. That's what we do best. Therefore it has to be monitored non stop.
But to step on it and destroy it, shut it down? That kind of thinking is pathological.
Quote:
As to the specific technical argument, you're saying that the reactor liquid would boil away, extinguishing any chance at criticality, which I would agree with if we were certain that this is what would happen, but which we are not certain of. In a pure evaporation scenario, you've made the argument (implicitly) that the solute will dissipate with evaporating solvent. This may not always be true. The boiling point of FLiBe is 1430 °C. The boiling point of ThF4 is 1680 °C. If the FLiBe eutectic boils off separately from the ThF4 (which I don't know one way or the other), then there's a temperature range where solvent evaporation leads to fuel concentration. Therefore, until we have experimental data on what happens when the liquid fuel-solvent mixture boils, it's improper to argue on grounds of plausibility that there's no risk here.But there's another way in which it seems you've misconstrued my original argument. The argument I made in my first post is that there's a plausible scenario where the solvent FLiBe does not evaporate away, but rather reacts away, leaving the solute, which contain all the fuel nuclides alone, with neither moderator nor coolant. This can happen simply at the liquid operating temperature, which is a few hundred degrees below its boiling point. The temperature rise from criticality of concentrated solute would happen, in this scenario, after the solvent is already gone.


I've offered a suggestion, a mere speculation based on few facts. You can't have, one way or another, an untact glowing ball penetrating the power plant.
My question is - what do you think corium can do? What's the worst case scenario in LFTR, and let's say it has a containment and passive lava dissipating system, something Chernobyl with much hotter accident didn't?

[Edited on 24-9-2012 by Endimion17]

blogfast25 - 24-9-2012 at 08:57

I agree with Watson that a considerable part of the visceral reaction that some people have re. nuclear energy, post-TMI and post-Chernobyl, is largely due to bad behaviour of said industry in its early days. GE and consorts really saw huge profits from very expensive projects when that technology was probably (with hindsight certainly) immature and far from as safe as it is today. See also France and Belgium, both countries with almost impeccable nuclear records and much less popular resistance to very widespread use of the technology.

France is a show case example of how not having natural energy resources can be turned into a profitable advantage. Here in the UK, if we finally decide to get a next generation reactors, they will probably be supplied by EDF.

While at lot of opposition to nuclear isn’t very rational, the ‘fascists’ exist only at the extremes of the movement and in a democracy a nuclear lobby cannot be allowed to run roughshot over what ordinary people think of that issue. It wouldn’t be a democracy otherwise.

Endimion17 - 24-9-2012 at 10:03

Quote: Originally posted by blogfast25  
I agree with Watson that a considerable part of the visceral reaction that some people have re. nuclear energy, post-TMI and post-Chernobyl, is largely due to bad behaviour of said industry in its early days. GE and consorts really saw huge profits from very expensive projects when that technology was probably (with hindsight certainly) immature and far from as safe as it is today. See also France and Belgium, both countries with almost impeccable nuclear records and much less popular resistance to very widespread use of the technology.

France is a show case example of how not having natural energy resources can be turned into a profitable advantage. Here in the UK, if we finally decide to get a next generation reactors, they will probably be supplied by EDF.

While at lot of opposition to nuclear isn’t very rational, the ‘fascists’ exist only at the extremes of the movement and in a democracy a nuclear lobby cannot be allowed to run roughshot over what ordinary people think of that issue. It wouldn’t be a democracy otherwise.


The problem with your reasoning is that most of the people who were alive and old enough to understand the mentioned bad behaviour are dead today, or old enough to not give a fuck.
It was the initial antinuclear movement that had something to offer because it was focused on the weapons. It was several decades ago and it's over. The circumstances are different. Granted, the nuclear lobby still exists (every industry has one), and it's quite weak compared to the fossil fuel one, but now we've got the quasi-green lobby, too. You know, the ones that would turn a country's money into dust just to "put a PV panel on every house 'because it's good for the environment' ", and they secretly receive bribe from cheap manufacturers of silicon products.

The 60's and the 70's were marked by a battle between the military industry machine that didn't give a flying fuck about anything and kept blowing up shit in the Pacific, and the rising environmental concernes backed up by more civilized people. People were fed up with nationalistic, right wing bullshit and they had every right to stand up against it. Hell, I'd march against them, too.

Today, that green plant that promised a better future split into two - the quiet and rational one, backed by science, and the louder one that has the money and the power. And people believe them "because they're green". That's all they have to do. They show up, they scream and point fingers, and people trust them just because they exist. That's dangerous because it's uncontrolled.
They've gained a lot of popularity because of their founders' old battles. Ironically, some of those founders became their opponents. I hope we all know the story of one of the founders of Greenpeace.

I don't think things vital to the foundations of one country should be in the hands of "the majority". Energy, water, food, human rights, etc. You can't have the majority deciding on that. There has to be a professional circle of highly educated people who can decide.
The majority is always stupid. It's a pile of NIMBYs. If the government one day decided to listen to the majority on important subjects, the whole system would come apart. Why going to schools? Who needs math? Let's not vaccinate people! Let's not use pesticides! Why prisons if you can kill the motherfuckers, and you can even do it in the middle of a street? I don't want "those people" to be able to marry, it hurts my religious feelings!

The list goes a long way. People are just incredibly stupid and if they weren't controlled, mayhem would occur. First slowly, then a civil war.
Democracy is a weird thing and should not be confused with anarchy.
It does not mean that someone's ignorance is just as good as someone's ignorance. (Asimov's thoughts)

[Edited on 24-9-2012 by Endimion17]

blogfast25 - 24-9-2012 at 12:39

Endi:

Re. your first point: culture doesn’t work like that. People will always collectively ‘remember’ things, like it or not. And I think mainstream environmentalism has come some way towards acceptance of nuclear, more than you make out. Ironically (and as a consequence of the low death toll in the Japanese disaster), one of nuclear’s main detractors, George Monbiot, recently declared himself converted on nuclear as a 40 year patch.

And careful with your ‘Council of Experts’ idea: it’s a recipe for power elites, lobbies, special interest groups [cough!] etc to muscle in and turn democracy (deeply flawed as it is) into a plutocracy/kleptocracy. I mean, hey, who could be better placed to decide on these things than the good old military-industrial complex itself, eh? ;-)

Yours seems to be the idea of the ‘Benign Dictatorship’, I’m much too old to like that. Much as I despair of many of my fellow citizens’ opinions on several of the things you mention I don’t think they should be sidelined so easily. Conversely, on many things that I hold dear it seems it’s rather governments that decide things in ways that I think are hugely detrimental, not Joe Blokes.

Specifically in the case of complex technology like MSTR I’d really like to see the ‘council of experts’ that could decide on such a matter in an unbiased way.

meaniac - 24-9-2012 at 18:13

Reactor Safety has come a long way. The Fukushima disaster was certainly serious, but we need to keep in mind that these reactors survived one of the largest earthquakes ever recorded, followed by a disastrous Tsunami and still had minimal casualties. You could argue that a conventional power station under similar circumstances may have killed more people. A bit of perspective would be handy.
On Topic: I am very interested in molten salt reactors, but don't know enough to made any informed judgement. I'm hoping to find out more here. I suspect the corrosive qualities of the molten flourides and compatibility issues will decide one way or the other. What about a layer (few hundred tons I guess ) of boron oxide immediately below the pressure vessel?

Endimion17 - 26-9-2012 at 06:54

Quote: Originally posted by blogfast25  
Endi:

Re. your first point: culture doesn’t work like that. People will always collectively ‘remember’ things, like it or not. And I think mainstream environmentalism has come some way towards acceptance of nuclear, more than you make out. Ironically (and as a consequence of the low death toll in the Japanese disaster), one of nuclear’s main detractors, George Monbiot, recently declared himself converted on nuclear as a 40 year patch.

And careful with your ‘Council of Experts’ idea: it’s a recipe for power elites, lobbies, special interest groups [cough!] etc to muscle in and turn democracy (deeply flawed as it is) into a plutocracy/kleptocracy. I mean, hey, who could be better placed to decide on these things than the good old military-industrial complex itself, eh? ;-)

Yours seems to be the idea of the ‘Benign Dictatorship’, I’m much too old to like that. Much as I despair of many of my fellow citizens’ opinions on several of the things you mention I don’t think they should be sidelined so easily. Conversely, on many things that I hold dear it seems it’s rather governments that decide things in ways that I think are hugely detrimental, not Joe Blokes.

Specifically in the case of complex technology like MSTR I’d really like to see the ‘council of experts’ that could decide on such a matter in an unbiased way.



I don't think mainstream environmentalism has made any steps forward. If it did, the whole Japan situation just made it worse.

It's not a benign dictatorship. Pretty much all modern societies have educated people to decide about plenty of stuff. For example, education. Hillbillies can't vote to remove modern theory of evolution from the curriculum (well, they almost thwarted it in USA, but thankfully, the reason won the battle). Why should energy be differently treated from education? I am, of course, talking about basic decisions like what kind of power plant should be built, how much MWh should it provide, etc. Not stuff like "we'll destroy your town in order to make a big ass coal power plant".

There are some things about which general people shouldn't be asked for an opinion because they don't have the brain capacity to make a truly informed decision.
Quote: Originally posted by meaniac  
Reactor Safety has come a long way. The Fukushima disaster was certainly serious, but we need to keep in mind that these reactors survived one of the largest earthquakes ever recorded, followed by a disastrous Tsunami and still had minimal casualties. You could argue that a conventional power station under similar circumstances may have killed more people. A bit of perspective would be handy.
On Topic: I am very interested in molten salt reactors, but don't know enough to made any informed judgement. I'm hoping to find out more here. I suspect the corrosive qualities of the molten flourides and compatibility issues will decide one way or the other. What about a layer (few hundred tons I guess ) of boron oxide immediately below the pressure vessel?


One important thing to note is that the primary problem in Fukushima 1 wasn't nuclear. The reactors came to a full stop flawlessly. The quake was tremendous, and the pressure vessel remained intact, as well as the containment.
It was the electrical-diesel backup cooling system that failed, because of the wave. People who built them on the shore are the ones to blame. I mean, come on, they've built the diesel tanks on the low spot. Someone had to imagine what would happen if a wave came and pulled them out, together with the power lines. I've seen the detailed aerial photos. The wave just erased half of the goddamn outside utilities from the planet's surface.
To blame nuclear reactors is flawed reasoning. I blame the morons that kept quiet about the basic stuff. For god sake, they had to expect a tsunami will come one day.

This is why if someone wants to destroy a nuclear power plant, targeting the reinforced concrete fortress known as the containment is useless. It's the cooling system that needs to be erased. Power lines that connect the plant to the outside system and diesel storage. Thankfully, it's virtually impossible for anything other than an heavy aerial attack (carpet bombing, nuclear attack), a tsunami, or a fault like directly below the plant, to cause a meltdown.


Regarding the LFTR, there's no pressure vessel which would house the nuclear material, IIRC. That's one of the advantages of the design. PWRs are often frowned upon because they're high pressure cookers with the "burner" inside. RBMKs also don't have a pressurized nuclear material (if we count inert gas above 1 atm to keep the air out), but instead pipes with cooling water running through a hot graphite brick furnace.

PWR is fine, and the most widely tested technology. France (AREVA) has made an unbelieveable step forward in active safety systems, as well passive ones. It's space stuff, compared to typical 70's power plants still operating throughout the world.

blogfast25 - 26-9-2012 at 13:38

Endi:

Statements like:

"People are just incredibly stupid and if they weren't controlled, mayhem would occur. First slowly, then a civil war.
Democracy is a weird thing and should not be confused with anarchy."

...sound EXACTLY like promos for dictatorships: 'we can't leave it to those ignorant plebeians'.

The educated people you talk about are mostly just part of the general electorate. I think you seriously underestimate their influence on democratic decision making. Without them, you get Creationism in the mainstream curriculum. But also with a 'Council of Experts' made up of Tea Party nutters. Careful what you wish for!