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PostPosted: Nov 08, 2013 4:20 am 
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*Edit*
In this post I am referring to the two-fluid, graphite-moderated and –reflected, molten salt, thermal spectrum breeder reactor design started by ORNL in the 60s, and now being 'picked up' by Kirk Sorensen and Flibe Energy.
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I apologise in advance, I am very ignorant about LFTRs and am doing my best to expand my knowledge. I don't mean to offend anyone with my ignorance.

I know engineers generally hate the term "worst case scenarios", but I'm writing a paper and as such need to be able to represent the end of the safety spectrum. Referenced information would be very appreciated!

An example might be something of Chernobyl proportions, where the design was terrible and everything went wrong.

Containment structures of PWRs in the US have to be designed to withstand the impact of a large commercial aircraft (http://www.nrc.gov/reading-rm/doc-colle ... -0150.html). What would be the consequences of a LFTR being hit by a plane, or say, terrorists detonated a device right next to the reactor vessel?

What if the fuel reprocessing is for some reason impossible, reactive gases fail to get filtered (or something similar), causing a build up, resulting in an explosion? Or if there is a leakage of the blanket fluid, causing the inner fluid to overheat and cause a criticality event? The piping to the drain tank gets blocked, causing a criticality event etc.

Can anyone think of the worst possible consequences of an incident, and support their claims with verifiable information?


Last edited by Luke Moylan on Nov 08, 2013 11:59 am, edited 1 time in total.

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PostPosted: Nov 08, 2013 6:08 am 
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It is very difficult to answer your questions, because the LFTR concept is poorly defined. People don't even agree on whether it should be 1 fluid or 2 fluid, and other basic design questions. So we can't get into safety analysis.

We can make a few generic statements. Criticality safety can be designed for by going for negative coefficients of power and low reactivity reserve from having liquid fuelling. Volatility is low and stability is very high. So the salt won't do anything exciting.

Physical threats are also fairly easy to design out of the safety equasions. A bunker protects against aircraft crash and other missiles.

The most sensitive area is decay heat removal. Decay heat can't be shut down. Whereas a decay heat removal system can be shut down in many different ways. Some can be designed out but inherently a heat transfer system is more fragile than a bunker for physical protection, because you must efficiently transfer heat. That requires thin shells and such. Yet we can't transfer fission products, and we don't want this thin shell to break. This forces thicker materials but then that has worse heat tranfer... it is a design puzzle that has a number of solutions and most will work adequately, but we must be careful.

This is especially the case with things like offgas and volatiles processing. There we don't have volatility on our side, unlike in the fuel salt. If there are lots of processing vessels then there is lots that can break and spill volatiles into the containment. Still, if that containment is a bunker with filtered passive confinement, then I don't see any way for the nasties to get out. More of an investment protection issue. An offgas leak could potentially contaminate the containment so badly that the plant must be decommissioned, making this an area of great design attention (double walled piping, vessels, with rapid leak detection in the annulus, etc.).

My own approach is to first design failures out of the equasion altogether, rather than having redundant backups which could fail. If that is impossible then I follow the IAEA definition of passive safety, first attempt to solve the problem with the most passively safe solution, category A passive systems, like a double or triple walled pipe, if that is not sufficient then add category B or C system, etc.


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PostPosted: Nov 08, 2013 11:58 am 
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As Cyril said we start with trying to design out the risks.
1) strong negative reactivity coefficient - meaning when the fuel salt heats up the fission reaction slows down. Heating the fuel salt up by 100C pretty much automatically shuts down the fission reaction. Criticality accidents are not plausible in a thermal (graphite moderated) LFTR. It is less obvious with a graphite free LFTR design.
2) on-line refueling. Since the reactor uses a fluid fuel it is reasonable to add fuel each day. This means we can run the reactor with just enough fuel and we have to have things in an optimal configuration do achieve criticality.
3) no motive force. We keep things at atmospheric pressure with nothing to burn, change phase, or release large amounts of energy from chemical reactions. All this means that even if pipes break etc there isn't a strong force to push nasties into the environment.
4) by design we try to chemically trap the fission products. Almost all fission products form stable fluorides and are happy in the fuel salt. So even if you put the fuel salt out in the open very little radioactive material would propagate into the environment. Most of this happens with any extra effort on our part. The uranium is in the form of UF4. When the uranium fissions the bonds are broken and we get two fission products plus 4 atoms of fluorine. The fission products then bond to the fluorine to form stable compounds. There are a few exceptions that do not form fluorides - noble gases, noble metals, and iodine. These we have to deliberately plan for. When doing a safety analysis of a specific LFTR design these are the guys to track and hypothesize ways they might escape. Notice in particular that cesium forms a stable fluoride so once a fission product is cesium it won't travel into the environment.
5) In general, the most problematic fission products are 137Cs, 134Cs, 90Sr, and 131I. 134Cs is formed directly so it immediately becomes CsF and is chemically locked up. 137Cs has a 4 minute half-life Xe precursor that is mobile in the environment. But if the reactor holds together for 40 minutes the Xe decays away. As long as we keep fluorine atoms available where-ever the Xe could be we will lock up the Cs. This takes some deliberate design on our part to deliberately place fluorine donor compounds in the off-gas system where we move the Xe every minute or so. Similarly for 90Sr, it has a precusor of 90Kr with a 30 second half-life. So we need fluorine donor compounds to trap the Sr when 90Kr decays. Due to the short half-life if we survive the first 5 minutes then this problem is gone. That leaves the iodine. It's behavior in the fuel salt is complicated and not fully understood. It does seem to be volatile and thus a possible escapee. Cyril and I have traded ideas for trapping the iodine chemically - but so far they are just ideas. I should hasten to point out that the iodine still doesn't have the motive force to push it into the environment but we'd prefer to have both defense mechanisms of nothing to push radioactivity into the environment and chemical securing the fission products so that they don't travel easily.

I gave you a long answer to a short question but I hope it gives you deeper understanding of why a LFTR (especially a thermal one) can be designed to be safe even in a large scale deployment. I should note though that nothing anyone can design will completely protect us from literally scaring ourselves to death. Many people in Japan were killed not by the problems at the nuclear power plant but by the excessive fear and poor decisions that resulted.

A few examples:
1) If there wasn't excessive fear then the reactors could have been vented before they blew up. But concern over a minor release of radioactive gases postponed the decisions to vent and led to bigger problems. (but there should have been filters present to trap the radioactive gases).
2) the evacuation of sick people when there wasn't the proper means and place to move them killed tens. If the Japanese had stuck with their original plan to shelter in place they would have been fine. The US had a significant role in changing Japan's mind. (Our head of the NRC in particular).
3) the decision to shutdown all reactors - even ones with no problems - resulted in power shortages that mean lack of cooling during a heat wave which killed folks. My guess is that there was a corresponding lack of heating during the cold times and probably this had a similar impact - though I haven't seen reports specifically on the cold problem.
4) the current decision to retain treated water because it still contains tritium means there is a large body of water stored in tanks. I hope this doesn't lead to problems later on.
5) the current fear nonsense about moving the spent fuel is scaring people. Hopefully, it won't scare anyone to death but it likely will contribute to decisions to rely ever more on natural gas. It is absolutely certain that there will be people killed by problems with the natural gas. (It happens every year so often that it isn't news).


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PostPosted: Nov 08, 2013 12:51 pm 
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Cyril,

Cyril R wrote:
It is very difficult to answer your questions, because the LFTR concept is poorly defined. People don't even agree on whether it should be 1 fluid or 2 fluid, and other basic design questions. So we can't get into safety analysis.


You're right, I'm guilty of perpetuating the ambiguity I'm trying to remove! I've edited my comment to reflect my intentions

Cyril R wrote:
Physical threats are also fairly easy to design out of the safety equasions. A bunker protects against aircraft crash and other missiles.


What I'm really after is the consequences in a terrible scenario. It would be nice to be able to design out any safety issues, but realistically increased safety measures directly result in increased cost. What would be the consequences of an explosion in the reactor if there was no containment structure/bunker? Do we know of any research conducted into the possible spread of radiation and dangerous products in such a scenario? Would having the fuel dissolved in liquid salt exacerbate the spread of radioactivity or limit it?

Cyril R wrote:
The most sensitive area is decay heat removal. Decay heat can't be shut down.


In his recent ThEC13 presentation, Kirk indicated that the fuel salt will not become 'recritical' if it is not in the reactor, as the neutrons are no longer being moderated by the graphite which is required to continue the reaction. This implies that even if the decay heat is not removed, it will not necessarily be a huge issue. Is this the case? Or will the decay heat build up if not removed and eventually melt the drain tank, resulting in an expensive clean-up scenario?

Cyril R wrote:
This is especially the case with things like offgas and volatiles processing. There we don't have volatility on our side, unlike in the fuel salt. If there are lots of processing vessels then there is lots that can break and spill volatiles into the containment. Still, if that containment is a bunker with filtered passive confinement, then I don't see any way for the nasties to get out. More of an investment protection issue. An offgas leak could potentially contaminate the containment so badly that the plant must be decommissioned, making this an area of great design attention (double walled piping, vessels, with rapid leak detection in the annulus, etc.).


I'm not familiar with the term "offgas". Could you briefly explain what it is in the context of a two-fluid LFTR?

What would be the impact of an explosion due to mishandling of volatile substances during processing?

Lars,

Thanks for your post...

Lars wrote:
3) no motive force. We keep things at atmospheric pressure with nothing to burn, change phase, or release large amounts of energy from chemical reactions. All this means that even if pipes break etc there isn't a strong force to push nasties into the environment.


I found this point you made to be of particular interest. I mostly agree with what you have said, except that there will of course be small pressures required across each of the pumps and heat exchangers etc.. Surely in the event of an explosion/fire there would be significant radiation released if we assume the containment chamber was somehow breached?

Lars wrote:
4) by design we try to chemically trap the fission products. Almost all fission products form stable fluorides and are happy in the fuel salt. So even if you put the fuel salt out in the open very little radioactive material would propagate into the environment. Most of this happens with any extra effort on our part. The uranium is in the form of UF4. When the uranium fissions the bonds are broken and we get two fission products plus 4 atoms of fluorine. The fission products then bond to the fluorine to form stable compounds. There are a few exceptions that do not form fluorides - noble gases, noble metals, and iodine. These we have to deliberately plan for. When doing a safety analysis of a specific LFTR design these are the guys to track and hypothesize ways they might escape. Notice in particular that cesium forms a stable fluoride so once a fission product is cesium it won't travel into the environment.


I read in a LFTR-debunker post (which I unfortunately can't find right now) that the danger in a LFTR is transferred from the reactor itself to the fuel reprocessing, which involves fluorine, which is very reactive. If the handling of the fluorine was to somehow go wrong...what would the consequence be? haha. I really just need more information from a definitive source, which I unfortunately can't locate! haha. Also if the there is an issue with reprocessing, and the other reactive gases are unable to be removed, what would be the worst case scenario of a reactive gas build up in the reactor?

Lars wrote:
Many people in Japan were killed not by the problems at the nuclear power plant but by the excessive fear and poor decisions that resulted.


Coincidentally, there was a "Current Affairs" program on this televised in Sydney, Australia, just 2 nights ago! Criminally, but as expected, the program made it seem like all nuclear technology was therefore the enemy.

The purpose of the paper I'm writing is to assess the ability of the specified LFTR to quell these fears (regarding safety, nuclear proliferation, and waste production and disposal). Obviously there are incredible amounts of misinformation being depicted in the media and online, so I am trying to create a "definitive" assessment (in mostly non-technical terms) of the technology.

I have just over a week before I need to submit my paper...haha.

Thank you both for your responses so far!


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PostPosted: Nov 08, 2013 2:30 pm 
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Nuclear plant safety can be thought of as the "3 C's). These are, control, cool, and contain.

Control means controlling the critical chain reaction. This can be inherently designed to be safe no matter what happens (terrorist explosions or whatnot).

Cooling is needed at all times. During normal operation the cooling is done with normal pump and heat exchange systems. For safety we are mostly interested in emergencies, when the normal system is not available. And you may also not have electricity. So the reactor will be shut down. Since a LFTR can and should be designed to have inherent criticality safety, we can assume the problem becomes the decay heat which occurs even after the reactor has been shut down. This heat cannot be turned off and must be cooled away from the reactor.

Contain refers to the highly radioactive substances which must stay in the reactor primarily. In an emergency, if it can't stay in the reactor it must stay in the containment.

Since LFTR has no serious safety issues with controlling the reactor, the scenarios to discuss are those relating to loss of cooling and/or loss of containment layers.

Decay heat is there even without a critical reactor. So I don't know what you heard from Kirk but decay heat cooling is something that is always necessary. Any molten salt reactor can be designed to have no large release of radiation even with all cooling systems failed. It requires special containment and shield design. It can make a giant mess but it can be contained due to the low volatility and lack of stored energy (no hydrogen, pressure buildup, etc.).

We are still not discussing a particular LFTR design so we can't get any further. If you have a specific design in mind like MSBR, DMSR, TMSR, Fuji-MSR, then we can go into more specifics.

Worst case scenario's, like you say, are not popular because there is no worst case. It can always get worse. Tomorrow we might all be dead from a 20 mile diameter asteroid strike. Extremely unlikely that astronomers have missed a large asteroid that is so close, but we can't say the probability is zero.

So should we design LFTRs or any other nuclear reactor to resist 20 mile asteroids? This means building all LFTRs at a depth underground that is not currently technologically feasible and even if it were feasible would be economically and practically impossible.

Clearly the scenario suggested and the design of a nuclear plant have a link. That is why you must have reasonable scenarios. If your scenario is any that is theoretically possible, then no nuclear plant will ever ever by safe, and neither will anything built with human hands.

For me the most severe scenario that I'd like to see a LFTR withstand is a long term complete loss of power combined with multiple pipe breaks/leaks combined with no operator action combined with a total malfunction of the control rods. The success criterium being no significant radiation release.

For less severe scenario's like only a loss of power plus no operator action, the success criterium for me would be no serious plant damage (ie being able to start up the plant again after minor inspection and maybe non-nuclear repairs).

What scenario do you have in mind to challenge a specific LFTR design?


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PostPosted: Nov 09, 2013 1:41 am 
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Cyril R wrote:
For me the most severe scenario that I'd like to see a LFTR withstand is a long term complete loss of power combined with multiple pipe breaks/leaks combined with no operator action combined with a total malfunction of the control rods. The success criterium being no significant radiation release.

What scenario do you have in mind to challenge a specific LFTR design?

Thanks again for your reply Cyril,

For my paper I'm looking at two sources for the design. The first is the ORNL theoretical design of a two-fluid LFTR (before the MSRE), the design papers on which can be found here (http://www.energyfromthorium.com/pdf/ORNL-4528.pdf). The second is Flibe Energy's design of the same reactor - unfortunately the most technical information I can find is in the slides from Kirk's presentations, the most recent being from (https://indico.cern.ch/getFile.py/acces ... fId=222140). Where there is a conflict between the two designs, I will assume Flibe Energy's design takes precedence, as it is more recent.

If we could please discuss the possible consequences of 4 separate scenarios?

1. Your worst case scenario described in your post.

2. An explosion next to the reactor and containment breach (I will need to assume something like this in my paper, as it is an argument that LFTR haters often bring up)

3. Several severe leaks in the LFTR pipework and a sustained fire onto which the salts are being poured.

4. An explosion in the continuous refuelling and processing plant.

I'm assuming a success criteria of radiation release, and operator/worker safety during the incidents.

Thanks again!


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PostPosted: Nov 09, 2013 2:37 am 
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Luke Moylan wrote:

2. An explosion next to the reactor and containment breach (I will need to assume something like this in my paper, as it is an argument that LFTR haters often bring up)


One could always hypothesize a bunker busting missile, followed by high explosive missile intended to scatter material widely. If you are going to hypothesize such stuff then please do a comparitive to what would happen if the same attack were directed at Congress or a football stadium.

Quote:
3. Several severe leaks in the LFTR pipework and a sustained fire onto which the salts are being poured.

A sustained fire needs a fuel source. By design we are not including such a fuel source inside the containment.

Quote:
4. An explosion in the continuous refuelling and processing plant.

Now you are getting closer to something to fuss about - specifically in the processing. Working with hot fluorine gases is not trivial. Industry does it but still not trivial. I think we can keep this risk moderate by keeping the processing plant size and throughput modest. But the processing plant is the most speculative portion of a LFTR design. So at this point we would have to consider simply that these are design goals.

I would add risks in the off-gas storage system, and most especially the off-gas initial processing stage. This seems to me to be the toughest part of the reactor.

Quote:
I'm assuming a success criteria of radiation release, and operator/worker safety during the incidents.

It seems pretty tough to claim worker safety when you are assuming incidents that blow away the massive containment or have severe leaks of 650C molten salt combined with sustained fires.


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PostPosted: Nov 09, 2013 5:15 am 
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Lars has already answered mostly.

Scenario 2, explosion, well what kind of explosion? The reactor building is designed for aircraft crash. Takes a really big explosion to damage such a structure, because air (shockwave) has a tiny density compared to things like jet engines. You'd need something really substantial, and there will be vehicle barriers that prevent things like large truck bombs from getting close enough. External explosions caused by low tech terrorist weapons are not a major threat as I see it.

Scenario 3, sustained fires, is something that can be designed out as well. The primary reactor cell is inerted with noble gas. No fires possible. There are also tiny or no quantities of materials present that can sustain a fire. Some plastics from pump electronics can smoulder and produce smoke. But not a sustained fire.

Scenario 4. Reprocessing explosions - also eliminated by inerted cells and relatively small quantities present at any one time in the cells. There would probably be larger stores of fluorine and perhaps hydrogen away in a non-nuclear building, any explosion there is just a "regular" industrial issue. No radiation involved.

Scenario 1. This is the kind I'm most interested in because it could plausibly be caused by an eartquake much higher than the plant design basis. Earthquakes are easily the most limiting natural external events, because they can take out multiple systems like electricity plus cause pipes to break plus cause certain areas to be inaccessible, and they can do this instantly. ORNL's proposal (and still Kirk's I think) is to use drain tanks. A limiting fault would be a break of the drain tank nozzle or distributors by the eartquake, spilling the fuel salt out of the tank into the drain cell. Typically there's a cooling system inside the tank, so salt outside the tank means most or all decay heat removal is lost. This is a serious situation that will have to be investigated for drain tank options. Speculating on what would happen, likely overheating of the cell and boiling of the salt, collapse of the drain cell structure, salt and iodine go into the reactor building, where they condense and settle on the inside of surfaces of the reactor building. This should provide sufficient surface area for cooling but would have to be calculated. With a passive filter, no large release of iodine and cesium, but probably some release of noble gasses (no big deal). And a giant expensive mess to clean up.

Some of these unlikely failure modes of drain cells have interested me in looking for other solutions, primarily cool-in-vessel combined with cool-through-containment strategies.


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PostPosted: Nov 09, 2013 5:46 am 
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Lars and Cyril,

I'm sorry if you find my ignorance insulting. I'm just trying to get an idea of the bounds of possibility regarding LFTR safety. I agree that it's difficult to state what the consequences would be of an event that seems impossible, especially when safety can be easily designed to avoid certain events, but what I really need to know is what the consequences would be.

Lars wrote:
One could always hypothesize a bunker busting missile, followed by high explosive missile intended to scatter material widely. If you are going to hypothesize such stuff then please do a comparitive to what would happen if the same attack were directed at Congress or a football stadium.

I'm trying to understand what the consequences of such an incident would be. Depending on what I discover, I already have the intention of "turning around" the argument, depending on the actual risks with the LFTR, and make a similar statement to what you are saying. From a terrorist standpoint, it would assumingly be more effective to put the same amount of effort into targeting something else (such as a stadium). Having said this, I still need to know what would be released in the case of a containment breach, and what kind of spread could we expect to see?

Lars wrote:
A sustained fire needs a fuel source. By design we are not including such a fuel source inside the containment.

If the temperature is high enough and oxygen is present, even steel and graphite can undergo sustained combustion. But, I appreciate your debunking of my scenarios, as it is just a learning process for me. Having said this, when they were designing the Fukushima plants, it seemed outside the realms of possibility that the reactor would be shut down, and that all backup generators would be knocked offline. If trying to develop "what if" situations that would be worst scenario so that I can either shut up the haters (if there are practically no consequences), or say that the worst scenario would lead to "...".

Lars wrote:
4. An explosion in the continuous refuelling and processing plant.
Now you are getting closer to something to fuss about - specifically in the processing. Working with hot fluorine gases is not trivial. Industry does it but still not trivial. I think we can keep this risk moderate by keeping the processing plant size and throughput modest. But the processing plant is the most speculative portion of a LFTR design. So at this point we would have to consider simply that these are design goals.
I would add risks in the off-gas storage system, and most especially the off-gas initial processing stage. This seems to me to be the toughest part of the reactor.

I'm exhibiting my ignorance again in that I do not know what is being referred to by the term "off-gas".
What would be released in the case of a processing plant accident?

Lars wrote:
I'm assuming a success criteria of radiation release, and operator/worker safety during the incidents.
It seems pretty tough to claim worker safety when you are assuming incidents that blow away the massive containment or have severe leaks of 650C molten salt combined with sustained fires.

That is why I am posing these as worst case scenarios. I am trying to get an idea of what the radiation spread would be in comparison to say, Chernobyl, and what the effect of radiation would be on the workers exposed to the radiation while trying to limit/clean up after a disaster.

Are these not the kind of scenarios that have to be considered in NPP design? If the NRC has criteria for planes flying into the containment building for PWRs, surely the "worst case scenario" hypotheticals get pretty out of hand?

Thank you both for your continued responses!

Cyril R wrote:
Scenario 1. This is the kind I'm most interested in because it could plausibly be caused by an eartquake much higher than the plant design basis. Earthquakes are easily the most limiting natural external events, because they can take out multiple systems like electricity plus cause pipes to break plus cause certain areas to be inaccessible, and they can do this instantly. ORNL's proposal (and still Kirk's I think) is to use drain tanks. A limiting fault would be a break of the drain tank nozzle or distributors by the eartquake, spilling the fuel salt out of the tank into the drain cell. Typically there's a cooling system inside the tank, so salt outside the tank means most or all decay heat removal is lost. This is a serious situation that will have to be investigated for drain tank options. Speculating on what would happen, likely overheating of the cell and boiling of the salt, collapse of the drain cell structure, salt and iodine go into the reactor building, where they condense and settle on the inside of surfaces of the reactor building. This should provide sufficient surface area for cooling but would have to be calculated. With a passive filter, no large release of iodine and cesium, but probably some release of noble gasses (no big deal). And a giant expensive mess to clean up.


This comment in particular has the kind of information I'm looking for, as it's the kind of musing that I can look into!


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PostPosted: Nov 09, 2013 7:41 am 
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Quote:
If the temperature is high enough and oxygen is present, even steel and graphite can undergo sustained combustion.


In pure oxygen, yes. That's nowhere to be found in or near a LFTR though.

In air, it's a completely different story. You can actually take a pool of liquid iron at 2500 degrees Celsius and let it sit with its top exposed to air. No fires. Graphite is similar. It just doesn't sustain a fire in air. Graphite won't burn in air at all, to get that you must get either sublimation temperatures of >3600 Celsius, that will generate flammable carbon gas (yikes!), or a strong oxidiser. Rest assured that graphite will never get to this temperature, for the simple reason that all fuel salt (the heat source) will have long boiled away before that point. And strong oxidisers in quantity are not present in the primary or even secondary loop. So, no graphite fires in air for a LFTR. Ever.

ORNL did some fun tests with molten nitrate-molten fluoride mixtures in contact with graphite. The graphite didn't burn, but did generate a lot of gas bubbles (likely carbon monoxide).

We can safely rule out sustained fire reactions with fuel salt. It just isn't physically reasonable.


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PostPosted: Nov 09, 2013 8:36 am 
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Well that's good to know. I have heard of incidents where steel has burned in air on ships, so I can't imagine what was burning to get the steel to that temperature! I read previously about the experiments on graphite, so that's a plus as well. I think it's a common misconception that graphite has the same combustion temperature as coal.

If you were writing a paper on 2-fluid LFTR safety, do you have any papers you would reference that I could use in my paper?


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PostPosted: Nov 09, 2013 10:35 am 
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Luke Moylan wrote:

If you were writing a paper on 2-fluid LFTR safety, do you have any papers you would reference that I could use in my paper?


Nope. One of my eyesores in the MSR field - far too little safety analysis being done. Certainly not much work in two fluid.

I helped write and re-write much of the Wiki article on LFTR. It needs more editing but you can find much on safety there in general terms.

http://en.wikipedia.org/wiki/Liquid_flu ... um_reactor


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PostPosted: Nov 09, 2013 11:22 am 
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Haha, first time I've ever "talked" to someone that has written a Wiki article!

I've actually be referring to it a lot, but the thing about academic papers is that I then have to go and found academic references for things that Wiki told me in the first 5 minutes of my search, haha.

However I can also write that there have been insufficient safety studies performed, which I guess is much more valid than trying to find unverifiable information.

Thanks again!


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PostPosted: Nov 10, 2013 7:47 pm 
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I'm looking for inspiration from some of the safety calculations performed for the MSRE (I know it's a single-fluid LFTR), and I would like to know if I'm reading this graph correctly.

http://www.energyfromthorium.com/pdf/ORNL-TM-0251.pdf

On page 7, we have a graph representing a fuel pump failure with no corrective action taken. After about 65 seconds we have the fuel reaching a max. temp. of just over 1400 F, which is about 760 C.

Is this indicating that even when left to its own devices, the MSRE was largely self-controlled? This temperature should be within capability of the graphite, and reactor vessel to handle, shouldn't it?

I'm assuming these figures are based on the 235U since the report is from '62. Would there be a significant change when going to 233U?

If we adapt the same scenario over to the 2-fluid LFTR, I'm thinking we'll see a similar response? But if the blanket salt is lost, and the fuel salt has a pump failure, I'm also thinking it won't be as self correcting due to the neutron availability for fission?

Please enlighten me with your opinions.


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PostPosted: Nov 10, 2013 8:51 pm 
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Also an additional question, if you guys don't mind.

In the event of a fuel salt spill in the cell complex of a 2-fluid reactor, the containment buildings would retain the majority of the radiation, no worries. But when the salt cools and solidifies, it produces Fluorine gas, which is very reactive. The Fukushima incident involved the build up of H2 inside the containment structure, which then exploded, because there was no passive filter. Are there current technologies that can passively filter F2?

I can't find any results with a google search.

Thanks!


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