Liquid Fluoride Thorium Reactor

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LFTR has a complex radiological path, and all of it is running at molten fluoride temperatures. Molten fluorides are NOT fun things to work with, they are very active. There are significant engineering hurdles for making a 700 C Material that can handle fluence for a reactor. Since there is no fuel loading - additional reactivity is inserted as needed from 233U-F4 salts in storage as needed, and fission products are removed in a chemical treatment of the main coolanant/fuiel salt, you're going to need materials which can handle 10^15 n/cm^2/s at 700 C for decades, not just a few years.
I can understand that but some of the Oak Ridge scientists who have worked with this type of reactor seem to think it really wouldn't be that big of a deal to figure out, here is a link:

Also, don't we have better suited materials today than these guys had 47 years ago?
Are the materials the biggest concern for building this type of reactor?
 
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I can understand that but some of the Oak Ridge scientists who have worked with this type of reactor seem to think it really wouldn't be that big of a deal to figure out, here is a link:
I just realized that interview is kind of lengthy, Dick Engel gives his thoughts about these materials at timeframe 23:10 (although I found the interview as a whole really quite insightful).
 
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I just realized that interview is kind of lengthy, Dick Engel gives his thoughts about these materials at timeframe 23:10 (although I found the interview as a whole really quite insightful).
TL;DL: "we kinda sorta thought we might be able to solve the corrosion problems at some unspecified point in the future because we did a few lab tests"

Yeah. Well.
 
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Are the materials the biggest concern for building this type of reactor?
One of the. There is also a big concern with designing adequate valves and things of that nature.
 
Building a small reprocessing plant near every reactor also doesn't sound inspiring. Those things are complex, expensive, and deal with very nasty stuff.
 
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Building a small reprocessing plant near every reactor also doesn't sound inspiring. Those things are complex, expensive, and deal with very nasty stuff.
As I get it the reprocessing would be part of the reactor (or at least the block), not a separated plant.
 
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TL;DL: "we kinda sorta thought we might be able to solve the corrosion problems at some unspecified point in the future because we did a few lab tests"

Yeah. Well.
If you are going to quote someone it must be accurate:

Dick Engel during his interview by Kirk Sorenson was asked, “Did the people on the program, in particular the chemists and material scientists feel that corrosion was an insurmountable problem?”

Engel replied, “Uhh, no, I think the people that I dealt with, or spoke with, said ‘okay this is an issue, specifically the tellurium issue but we can get around that’. And some of the subsequent work, subsequent to the initial shutdown they did some experimental work that bode very favorably for an ability to solve that issue.”

Coming from an engineer that has actual experience with this type of reactor it would seem reasonable to assume the materials are not as big an issue as you have thought.
 
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Building a small reprocessing plant near every reactor also doesn't sound inspiring. Those things are complex, expensive, and deal with very nasty stuff.
I thought for LFTR's this was part of the reactor and not some 'separate' re-processing plant. I understand that the liquid salts are dangerous to work with but are these systems by any means as complex (or dangerous for that matter) as the way our current nuclear reactors are run?
 

mheslep

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LFTR has a complex radiological path, and all of it is running at molten fluoride temperatures. Molten fluorides are NOT fun things to work with, they are very active. There are significant engineering hurdles for making a 700 C Material that can handle fluence for a reactor. Since there is no fuel loading - additional reactivity is inserted as needed from 233U-F4 salts in storage as needed, and fission products are removed in a chemical treatment of the main coolanant/fuiel salt, you're going to need materials which can handle 10^15 n/cm^2/s at 700 C for decades, not just a few years.
I'm not sure why it must be so that material lasts the life of the reactor, when the design specifies the fluoride salt can be drained away from the fission core / moderator area at any time, allowing replacement of the core material (graphite?) at whatever schedule desired.

Yes there will need to be thorough certification process for material in contact with the salt (Hastelloy-N?), but then again that effort should be seen in the context of the conditions which the LFTR would replace: a PWR with 153 atm water at 300C and fuel reaching 600C in zircalloy, also w/ 10^15 n/cm^2/s.
 
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mheslep

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I thought for LFTR's this was part of the reactor and not some 'separate' re-processing plant. I understand that the liquid salts are dangerous to work with but are these systems by any means as complex (or dangerous for that matter) as the way our current nuclear reactors are run?
I think the point was, built-in or loosely coupled, the reprocessing step is required for LFTR which adds significant complexity that existing PWR/BWRs don't require.

On the other hand, the advantage of LFTR over PWR/BWR is that i) the fuel enrichment / production step is greatly simplified or goes away entirely, ii) waste is greatly reduced and the waste that is produced has a much shorter half life, iii) no 150 atm water/steam to contain.
 
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I think the point was, built-in or loosely coupled, the reprocessing step is required for LFTR which adds significant complexity that existing PWR/BWRs don't require.

On the other hand, the advantage of LFTR over PWR/BWR is that i) the fuel enrichment / production step is greatly simplified or goes away entirely, ii) waste is greatly reduced and the waste that is produced has a much shorter half life, iii) no 150 atm water/steam to contain.
I would imagine given a choice of chemical seperation vs. isotopic, chemical will always be the easier path so long as rates of reaction are good. The idea that we shouldn't develop LFTR 'cause we haven't done it yet' seems absurd.

If the advocates are correct and the LFTR is capable of doing what they say I am on board, but getting the rest of the public and the political will in Washington will likely become the biggest challenge.
 

mheslep

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I would imagine given a choice of chemical seperation vs. isotopic, chemical will always be the easier path so long as rates of reaction are good. ...
Different problems. Unlike enrichment of uranium, the chemicals in a LFTR will have strong gamma and beta emitters, and the process will necessarily be in close proximity to an operational reactor.
 
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...Unlike enrichment of uranium, the chemicals in a LFTR will have strong gamma and beta emitters, and the process will necessarily be in close proximity to an operational reactor.
Okay, is it that the gamma and beta radiation will interfere with the chemical reactions? or are there problems with shielding for personel? both? or something else I am completely missing?
 
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I'm not sure why it must be so that material lasts the life of the reactor, when the design specifies the fluoride salt can be drained away from the fission core / moderator area at any time, allowing replacement of the core material (graphite?) at whatever schedule desired.

Yes there will need to be thorough certification process for material in contact with the salt (Hastelloy-N?), but then again that effort should be seen in the context of the conditions which the LFTR would replace: a PWR with 153 atm water at 300C and fuel reaching 600C in zircalloy, also w/ 10^15 n/cm^2/s.
I suppose one could do a tubesleeve system, although swelling issues are significant, and then replace the tubes when they seem to have lost cohesion. The lack of significant pressure will also alleviate the material concerns; you can be more brittle when your hoop stresses are lower.

Since ZrF4 was used as fluoride salt component in various MSRs, I'd expect Zircaloy is right out as a tubing material; The temperature range puts us into SiC or ZrC ranges; but they are non-ductile. I expect ODS alloys will be the likely tubing.

Of course, this is assuming we can't separate the corrosion resistance and ductility under radiation problems; if we can work out a reasonable method for SiC coating parts that stands up to radiation and thermal changes then almost all corrosion difficulties can be ignored, and the structural material can be chosen on retention of ductility alone.
 
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I suppose one could do a tubesleeve system, although swelling issues are significant, and then replace the tubes when they seem to have lost cohesion. The lack of significant pressure will also alleviate the material concerns; you can be more brittle when your hoop stresses are lower.

Since ZrF4 was used as fluoride salt component in various MSRs, I'd expect Zircaloy is right out as a tubing material; The temperature range puts us into SiC or ZrC ranges; but they are non-ductile. I expect ODS alloys will be the likely tubing.

Of course, this is assuming we can't separate the corrosion resistance and ductility under radiation problems; if we can work out a reasonable method for SiC coating parts that stands up to radiation and thermal changes then almost all corrosion difficulties can be ignored, and the structural material can be chosen on retention of ductility alone.
Are there issues with using Hastelloy N that were not adressed during the running of the research reactor at ORNL or are these simply better choices (cost, durability, etc.) by comparison due to material advancement in the last half century?
 

mheslep

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I suppose one could do a tubesleeve system, although swelling issues are significant, and then replace the tubes when they seem to have lost cohesion. The lack of significant pressure will also alleviate the material concerns; you can be more brittle when your hoop stresses are lower.

Since ZrF4 was used as fluoride salt component in various MSRs, I'd expect Zircaloy is right out as a tubing material; The temperature range puts us into SiC or ZrC ranges; but they are non-ductile. I expect ODS alloys will be the likely tubing.

Of course, this is assuming we can't separate the corrosion resistance and ductility under radiation problems; if we can work out a reasonable method for SiC coating parts that stands up to radiation and thermal changes then almost all corrosion difficulties can be ignored, and the structural material can be chosen on retention of ductility alone.
We may be talking about two different things.

In the case of a liquid molten salt reactor, it seems to me there are two primary materials to select. The first is the moderator, which will suffer the neutron flux, but has little structural support responsibility. The ONR experiment used a graphite block w/ channels through which the salt was pumped. I assume that's still the first choice for a moderator. The second material is for structural containment. It receives relatively small neutron flux, high radiation, and must structurally contain the ~700C salt. ONR used Hasteloy N.
 

mheslep

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Are there issues with using Hastelloy N that were not adressed during the running of the research reactor at ORNL or are these simply better choices (cost, durability, etc.) by comparison due to material advancement in the last half century?
Yes there's a problem that was recognized but not yet addressed (AFAIK) in an operation. It is mentioned in the video interview link you provided and on the MSR experiment wiki page. They found that Tellurium, a fission product, causes cracking presence of radioactivity in the alloy ONR used. This would not be trivial thing to test.
 
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Yes there's a problem that was recognized but not yet addressed (AFAIK) in an operation. It is mentioned in the video interview link you provided and on the MSR experiment wiki page. They found that Tellurium, a fission product, causes cracking presence of radioactivity in the alloy ONR used. This would not be trivial thing to test.
Agreed, but certainly possible.

Here is another interview with Dick Engel where he discusses this exact problem, it rings deeper than just the Tellurium (which it seems the material scientists had a solution for)

http://www.youtube.com/watch?v=ENH-jd6NhRc&feature=player_embedded

The question is raised at 17:25 and goes to 20:56, although (once again) I really found the discussion as a whole very interesting.

I like Dick Engals take on how to test materials for future reactors, same link but starting at time frame 19:41.
 

mheslep

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...

The question is raised at 17:25 and goes to 20:56, although (once again) I really found the discussion as a whole very interesting.
Yes I'd seen it previously. I just watched it again and Engel raised an obvious point that I missed before. He points out that if the Te corrosion problem is solved, the overall corrosion problem may not be solved because another element might cause trouble. The larger point being that fission of course means a large chunk of the periodic table would be present, everything from gallium to hafnium, including the very reactive alkali and halogen groups. Does this mean a chemical analysis the interaction of most of the elements in the periodic table against Hasteloy N must be done under LFTR conditions?

One of the advantages of LFTR is supposed to be that high burnup and low waste is possible in part because fission poisons, esp. xenon, can be chemically removed from a liquid fueled reactor, unlike a solid fueled reactor which must have the fuel replaced every couple years. But while targeting the removal of some elements is surely feasible, I doubt it is so easy to remove most of the periodic table.

It may be that in the case of long term corrosion the issue turns in favor short turn fuel supplies, as while fission also generates products in the solid fuel Zirc alloy rods, they're pulled out of service while LFTR is intended to keep going for 30 years or so.
 
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mheslep

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I've just read some of the critical final report on the Molten Salt Reactor Experiment written by the AEC in 70's after the shutdown. I knew of its existence but had avoided it given the politics of the time heavily favoring light water reactors and liquid metal breeders, and I thought it biased.

The structural material discussion starts on page 30. The argument seems valid, if overly absolute ("not suitable").

http://www.energyfromthorium.com/pdf/WASH-1222.pdf
 

Astronuc

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I've just read some of the critical final report on the Molten Salt Reactor Experiment written by the AEC in 70's after the shutdown. I knew of its existence but had avoided it given the politics of the time heavily favoring light water reactors and liquid metal breeders, and I thought it biased.

The structural material discussion starts on page 30. The argument seems valid, if overly absolute ("not suitable").

http://www.energyfromthorium.com/pdf/WASH-1222.pdf
On page 32 of WASH-1222 is the statement:
"In addition to the intergranular corrosion problem, the standard Hastelloy-N used in the MSRE is not suitable for use in the MSBR because its mechanical properties deteriorate to an unacceptable level when subjected to the higher neutron doses which would occur in the higher power density, longer-life MSBR."

Note that MSRE was only 8 MW (without the electrical generation system, and with off-line batch processing), while the MSBR was planned for 2250 MWt (1000 MWe) and use of on-line continuous processing. See Table III, p. 21 of WASH-1222.

Nickel is problematic in any neutron environment. It absorbs neutrons and becomes active (producing Co-58 and some Co-60) and suffers from an (n,α) reaction. An alloy with lower Ni content would be preferable, something more along the lines of more Cr-Mo (Hastelloys are Ni-Cr-Mo).

Several other technical issues are mentioned. The MSBR concept proposes high temerpature steam cycle, and that presents a challenge, particularly with respect to the heat exchanger, which basically can't be allowed to fail (leak), and then there is the materials compatibility issues between the steam and salt loop. The chemical separation part of the plant would also be challenging. Storage of Xe, Kr, I would be challenging, as well as ultimate disposition of the other fission products (ostensibly they would be converted to oxides and vitrified).

A large scale LFTR would not be a trivial undertaking.
 

mheslep

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On page 32 of WASH-1222 is the statement:
"In addition to the intergranular corrosion problem, the standard Hastelloy-N used in the MSRE is not suitable for use in the MSBR because its mechanical properties deteriorate to an unacceptable level when subjected to the higher neutron doses which would occur in the higher power density, longer-life MSBR."

Note that MSRE was only 8 MW (without the electrical generation system, and with off-line batch processing), while the MSBR was planned for 2250 MWt (1000 MWe) and use of on-line continuous processing. See Table III, p. 21 of WASH-1222.

Nickel is problematic in any neutron environment. It absorbs neutrons and becomes active (producing Co-58 and some Co-60) and suffers from an (n,α) reaction. An alloy with lower Ni content would be preferable, something more along the lines of more Cr-Mo (Hastelloys are Ni-Cr-Mo).
Yes, apparently He production inside the hastelloy is also a concern. However, it seems to me the neutron flux can be held to some arbitrarily low limit for the outer, structural support holding the salt, where no fission need occur, and with an arbitrary amount of salt or other neutron stops been the graphite-salt-core and the containment. So before WASH stated the material was "unsuitable" without caveat they might have demonstrated how a large neutron flux on the containment was unavoidable.

Several other technical issues are mentioned. The MSBR concept proposes high temerpature steam cycle, and that presents a challenge, particularly with respect to the heat exchanger, which basically can't be allowed to fail (leak),
The high temperature (~700C) is different from a PWR, but I don't know that such temperatures are more challenging than those encountered by any existing Brayton cycle system (e.g. jet engine)

and then there is the materials compatibility issues between the steam and salt loop. The chemical separation part of the plant would also be challenging. Storage of Xe, Kr, I would be challenging, as well as ultimate disposition of the other fission products (ostensibly they would be converted to oxides and vitrified)....
Yes, removal and storage of most every element below U would be required over the lifetime of reactor. There must be some kind of overall chemical architecture to address that issue, as working piecemeal against each and every fission product and their daughter products seems intractable.
 
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Yes I'd seen it previously. I just watched it again and Engel raised an obvious point that I missed before. He points out that if the Te corrosion problem is solved, the overall corrosion problem may not be solved because another element might cause trouble. The larger point being that fission of course means a large chunk of the periodic table would be present, everything from gallium to hafnium, including the very reactive alkali and halogen groups. Does this mean a chemical analysis the interaction of most of the elements in the periodic table against Hasteloy N must be done under LFTR conditions?

One of the advantages of LFTR is supposed to be that high burnup and low waste is possible in part because fission poisons, esp. xenon, can be chemically removed from a liquid fueled reactor, unlike a solid fueled reactor which must have the fuel replaced every couple years. But while targeting the removal of some elements is surely feasible, I doubt it is so easy to remove most of the periodic table.

It may be that in the case of long term corrosion the issue turns in favor short turn fuel supplies, as while fission also generates products in the solid fuel Zirc alloy rods, they're pulled out of service while LFTR is intended to keep going for 30 years or so.
What really matters is to what degree these elements formed, your statement is too broad and your link is for fissioning U235 not U233 but lets take a closer look anyway. You mentioned Gallium, pretty nasty stuff when in contact with most metals however it isn't even showing on your distribution scale for the graph you linked.

You had asked:
"Does this mean a chemical analysis the interaction of most of the elements in the periodic table against Hasteloy N must be done under LFTR conditions?"

No, its imperative to be more careful about allowing opinion to get in the way before looking at the facts.
 
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I've just read some of the critical final report on the Molten Salt Reactor Experiment written by the AEC in 70's after the shutdown. I knew of its existence but had avoided it given the politics of the time heavily favoring light water reactors and liquid metal breeders, and I thought it biased.

The structural material discussion starts on page 30. The argument seems valid, if overly absolute ("not suitable").

http://www.energyfromthorium.com/pdf/WASH-1222.pdf
I have heard about this report, seems to be fairly well known amongst the LFTR community; their opinions of it are less than favorable but a closer look should be done before forming an opinion on this matter.

On page 30 I noticed the report starts by talking about how the ORN scientists wanted to 'freeze' the salt along the walls to prevent corrosion in the flourinator, seems like a pretty clever idea, but is it feasable? The author thinks no but this report was not written by the scientists actually working on the project who had experience working with similar techniques; Time frame 8:16:

http://www.youtube.com/watch?v=ENH-jd6NhRc&feature=player_embedded

So now come the questions, how hard would it be? how much energy does it use? what is the cost of a system like this? From my own experience in refrigeration I don't think this would be difficult to add on. What is your opinion?
 
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A large scale LFTR would not be a trivial undertaking.
No doubt, but does it look promising enough to justify further develop?
Do you see the materials for the reactor as being the largest obstacle?

Yes, removal and storage of most every element below U would be required over the lifetime of reactor. There must be some kind of overall chemical architecture to address that issue, as working piecemeal against each and every fission product and their daughter products seems intractable.
I thought removal of these elements is part of the design with much talk (amongst advocates, so it should be investigated more thoroughly) about how they have high value for the industrial and research markets.

On another note, I don't see why we have to remove 'most every element below U' if their concentration is almost undectectable and there is little to no effect on the reactor itself. It would seem more important to concentrate on the elements that effect the lifecycle of the reactor i.e. materials longevity, efficiency, waste, etc.
 

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