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PostPosted: Sep 29, 2015 1:29 pm 
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jaro wrote:
darryl siemer wrote:
If this fuel cycle is properly implemented (i.e., with chlorine recycle) it'd just be a one-time cost.
This appears to presume burn-out of the Cl35.

My understanding is that with large bulk quantities, in any sort of realistic neutron flux, burn-out actually does not happen, even after decades of operation.

Have you verified whether burn-out occurs ? ....and what about the S35 ? ...is it better or worse than Cl35 ?

Thnx


My reply/comment had to do with justifying the cost of separating chlorine isotopes; i.e., that it'd only have to be done once per reactor.

No, I don't know what the the burnout rate would be but it's apt to be calculable.

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PostPosted: Sep 30, 2015 12:16 am 
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darryl siemer wrote:
jagdish wrote:
Separation of Cl37 should be convenient by centrifuge as gases with one atom of Cl in the molecule, like CH3Cl are there and you start with 25% of Cl37. Chlorides are often low boiling and convenient for fractional distillation. Kirk had recommended chloride reactors for burning of used LWR fuel.
http://www.forbes.com/sites/kirksorense ... -digester/
It is so logical that I wonder why it is not being pursued.
If it is seriously done, thorium will be reduced to a 'spice' to produce a better fissile U-233.

The most logical candidate molecule is HCl.

HCl is a strong acid. CH3Cl may be less corroding. The aim was to stress on feasibility. Lower overall cost is always important. HCl may, however, also cost less but difference may be marginal after Cl37 separation.


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PostPosted: Sep 30, 2015 1:17 am 
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I just realized that this thread is in the wrong folder - it's about chloride not fluoride reactor designs

Anyway, one problem with using a chloro-organic compound for any sort of isotopic separation is that 13C scrambles up mass differentials about 100 times more than just deuterium would be apt to.


I've done some more thinking about the 35S "issue" & now feel even more confident that it's unlikely to constitute a genuine problem. The basis for that conclusion began with a comparison of the product of the n,f cross section of 239Pu times its molar concentration to the n,p cross section of 35Cl times its molar concentration which suggested that about 10 moles of Pu will fission per mole of 35S generated. Next, since about 5% of the Pu's so fissioned will generate Mo atom-type FP and it would take either 3/2 or 2 atoms of S to make molybdenum sulfide (there are 2 such compounds), there ought to be plenty of nice fresh, super high surface area FP-type Mo atoms around to glom onto that equally nice & fresh 35S. That reaction would convert this S to something that would probably end up being skimmed off along with the other noble metal "scum" which would, of course, render it unable to corrode metallic Mo reactor components. Zirconium, another high yield FP it apt to act about the same way.

Even if that S did somehow escape reacting with its fellow transmutation and/or fission products & thereby rendered non corrosive, it's got a fairly short half life (88 days) that would prevent huge accumulations.

Of course this would have to tested.

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PostPosted: Sep 30, 2015 9:00 am 
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Even enriching chlorine directly might prove feasible.
Only a sixteenth the chlorine molecules would be double 37Cl molecules but chlorine is so cheap that that scarcely matters.
Especially since the bulk of the non double 37CL molecules would be 35+37 after enrichment.

We aren't looking for 99.99% enrichment here after all.


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PostPosted: Sep 30, 2015 5:28 pm 
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A 90% enrichment would reduce the sulphur challenge by factor 10.


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PostPosted: Oct 02, 2015 2:28 pm 
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Regarding sulfur, I am reading ORNL-4616 and there is a section discussing the treatment/removal of sulfur contaminants in a fluoride salt mixture. They developed a method using a simultaneous HF-H2 sparge treatment that removed the sulfur since it attacks nickel-based alloys when at elevated temperatures. It would be interesting to know if the HF-H2 sparge would work with a chloride salt mixture to remove the sulfur.


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PostPosted: Oct 02, 2015 11:09 pm 
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Jim L. wrote:
Regarding sulfur, I am reading ORNL-4616 and there is a section discussing the treatment/removal of sulfur contaminants in a fluoride salt mixture. They developed a method using a simultaneous HF-H2 sparge treatment that removed the sulfur since it attacks nickel-based alloys when at elevated temperatures. It would be interesting to know if the HF-H2 sparge would work with a chloride salt mixture to remove the sulfur.


It's an interesting idea but doesn't work thermodynamically. I ran one possible scenario (added increasing amounts of H2 to a mix of Mo metal, UCL3, & HCl) at 600 C with a state of the art thermodynamics program - the stable forms of the S throughout was a mix of MoS2 & Mo2S3 . The same thing happens when the amount of H2 is fixed and the amount of HCl increased. This means that spargable H2S doesn't form regardless of how much of either or both H2 and/or HCl is sparged (bubbled) through the molten salt.

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PostPosted: Oct 03, 2015 12:45 pm 
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A 95-99% purity of Cl-37 may suffice involving lower cost. Cl-35 could be used/sold as chlorine. HCl or CH3Cl could be used as such. Sulphur, in very minor amount, will precipitate and join the waste.


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PostPosted: Nov 06, 2015 8:09 am 
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darryl siemer wrote:
It's an interesting idea but doesn't work thermodynamically. I ran one possible scenario (added increasing amounts of H2 to a mix of Mo metal, UCL3, & HCl) at 600 C with a state of the art thermodynamics program - the stable forms of the S throughout was a mix of MoS2 & Mo2S3 . The same thing happens when the amount of H2 is fixed and the amount of HCl increased. This means that spargable H2S doesn't form regardless of how much of either or both H2 and/or HCl is sparged (bubbled) through the molten salt.
That's good to know, my hope was to use a H2 sparge as there are certainly many examples of H2S extraction from petroleum refining processes. Are there any other elements beside Mo that are reactive with S at these temperatures, that could be used as S grabbers?

I'm just thinking that if Mo is your primary structural material, making MoSx sounds quite unappealing.


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PostPosted: Nov 06, 2015 9:18 pm 
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Lindsay wrote:
That's good to know, my hope was to use a H2 sparge as there are certainly many examples of H2S extraction from petroleum refining processes. Are there any other elements beside Mo that are reactive with S at these temperatures, that could be used as S grabbers?

I'm just thinking that if Mo is your primary structural material, making MoSx sounds quite unappealing.


As said in my 30sep post, I feel that most or all of the 35S will end up reacting with FP Mo and/or Zr & thereby turned into a skimmable scum -there's plenty of 'em & they'll be present in a far more reactive form than is the core vessel's walls. However this is just another question that won't be definitively answered until someone in authority screws up enough courage to see that MSR relevant experiments are performed.

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PostPosted: Nov 07, 2015 7:03 pm 
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Sulphur compounds are not too stable, so the simple solution (pardon the pun) is to produce a chemically reducing environment. Without graphite and actinide solubility concerns, chloride reactors can potentially (pardon the pun again) operate much more reducing than fluoride fuel salts...

Sulphur should be quite harmless in such an environment. As long as you keep the water and oxygen away of course, same as any MSR.

MSR corrosion control 101 - keep it pure, keep it reducing.


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PostPosted: Nov 08, 2015 1:55 pm 
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Cyril R wrote:
Sulphur compounds are not too stable, so the simple solution (pardon the pun) is to produce a chemically reducing environment. Without graphite and actinide solubility concerns, chloride reactors can potentially (pardon the pun again) operate much more reducing than fluoride fuel salts...

Sulphur should be quite harmless in such an environment. As long as you keep the water and oxygen away of course, same as any MSR.

MSR corrosion control 101 - keep it pure, keep it reducing.


The form that sulfur would be in MoS2 (sulfide) is its most "reduced" form & therefore a MCFR's strongly reducing redox conditions (virtually all of its U & Pu in their trivalent forms) doesn't help in that respect. As far as purity is concerned, that can only be achieved with very high & therefore probably prohibitively expensive reprocessing rates...we've got to come with something that can iso-breed with a "dirty" fuel salt.

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PostPosted: Dec 06, 2015 9:37 am 
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Forgive the ignorance, but why should we need a fast chloride breeder when a thermal spectrum fluoride MSR is so easier and well known ? Obviously, besides to achieve an uranium breeding cycle that is useless (and perhaps politically unacceptable), in my view, is we already had a thorium breeding cycle


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PostPosted: Dec 06, 2015 10:44 am 
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Thermal Fluoride MSR cycles have their own engineering issues - for example graphite life, replacement and disposal.
A fast reactor using chloride salts avoids many of them, in favour of its own set of technical issues.

But they aren't obviously harder to deal with.


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PostPosted: Dec 06, 2015 1:19 pm 
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Alex P wrote:
Forgive the ignorance, but why should we need a fast chloride breeder when a thermal spectrum fluoride MSR is so easier and well known ? Obviously, besides to achieve an uranium breeding cycle that is useless (and perhaps politically unacceptable), in my view, is we already had a thorium breeding cycle
A thermal spectrum Th/U cycle reactor can catalyze the U/Pu cycle as well.

By simple, BoE numbers, I estimate we should be able to burn about 1 unit of NU (or LUFF) for every 4 units of Th. I find that almost magical because there are in our world, about 1 unit of NU for every 4 units of Th.

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