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PostPosted: Jul 30, 2010 1:50 pm 
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The point about chloride reactors is that the heavier chlorine atom allows very fast spectrums easier than fluorine in fluoride salts (besides the trifluoride solubility limit thing). However, why chlorine? The other halogens are all heavier still. Bromine, iodine and astatine might make interesting salt options for a fast reactor. Ok so don't ask me about uranium astatide ( :?: ), this might be a bit on the exotic side. But uranium bromide and uranium iodide have stable anhydrous salts with reasonable melting points. They could probably be used without a carrier salt, perhaps even a tri/tetra halide eutectic like Jaro has proposed for UF3/UF4.

Has anyone looked at this as an alternative to chloride MSRs?


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PostPosted: Jul 30, 2010 1:56 pm 
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Uranium tetrabromide:

http://www.ibilabs.com/Uranium%20Bromide,tetra.htm

Uranium tetraiodide:

http://www.ibilabs.com/Uranium%20Iodide.htm


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PostPosted: Jul 30, 2010 2:06 pm 
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Ah, astatine doesn't have a stable isotope... that explains a lot!


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PostPosted: Jul 30, 2010 2:30 pm 
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Cyril R wrote:
Ah, astatine doesn't have a stable isotope... that explains a lot!

Yeah, and I think there's something like 30g of it on the entire Earth at any given moment. Not that it would do you any good to get it, it would just disappear.


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PostPosted: Jul 30, 2010 3:05 pm 
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Wikipedia says 30 grams. Not much! Now that we're talking purely academic interests, I wonder about the other stability island somewhere up there, there's supposed to be a halogen species there. unun something they call those things, because no-one knows much about it :lol: The ununseptium might be a halogen.

Anyway, guess its down to iodine and bromine now.


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PostPosted: Jul 30, 2010 5:45 pm 
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Bromine has a neutronics problem, with lots of strong absorption resonances for both stable isotopes.

It doesn't have what I personally regard as chlorine's big drawback, the presence of a long lived isotope between the two stable isotopes.

Iodine's only stable isotope, 127 has a similar problem, as well as some chemical issues that I won't discuss.

I=129 is, of course, readily available as a fission product, although it produces a lot of whining and crying from anti-nukes.

The universe does not live by one set of anions alone, however, and were we to so choose, we could move beyond the halogens.

The best halogen, the only halogen that I see as acceptable, however is fluorine. I'm not a fan of molten chloride reactors.


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PostPosted: Jul 30, 2010 6:27 pm 
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Of course, if we did use I-129, keeping it safely inside a reactor, it could slowly be transmuted away, solving a disposal problem.

Might not do the neutron balance much good, though.


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PostPosted: Jul 30, 2010 8:04 pm 
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NNadir wrote:
The best halogen, the only halogen that I see as acceptable, however is fluorine. I'm not a fan of molten chloride reactors.

Why not? Neutron spectrum or chemical issues? While I find chloride salt reactors far less mature than fluoride reactors, the amazing neutron budget is kinda interesting.


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PostPosted: Jul 30, 2010 8:08 pm 
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Mike wrote:
Of course, if we did use I-129, keeping it safely inside a reactor, it could slowly be transmuted away, solving a disposal problem.

Might not do the neutron balance much good, though.


Many people like to talk about the sulfur iodine cycle, or close variants. It is certainly the most advanced cycle in terms of development, not likely the best, but definitely the most advanced.

(Thank you GA). I-129 is not a huge radiological hazard because of its long half life. One would not want to eat it, of course, but were the sulfur iodine cycle to go big time, I-129 (mixed with I-127 which is also a fission product) would be perfectly acceptable in this closed system.

Iodine is a relatively rare element, which makes its biology - the fact that it has biology - so interesting. I discussed this topic elsewhere on another website where I used to write:

Radioactive Isotopes from French Commercial Nuclear Fuel Found In Mississippi River.


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PostPosted: Jul 30, 2010 8:43 pm 
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dezakin wrote:
NNadir wrote:
The best halogen, the only halogen that I see as acceptable, however is fluorine. I'm not a fan of molten chloride reactors.

Why not? Neutron spectrum or chemical issues? While I find chloride salt reactors far less mature than fluoride reactors, the amazing neutron budget is kinda interesting.


Cl-37 has good neutron properties, I confess, but Cl-35 is not great.

Chloride reactor fans of course say, "separate the isotopes." This is possible of course, and would work, but I ask, why bother?

In general, with the exception of deuterium, because of its huge isotope effect, isotopic separations are economically and often energetically troublesome and imperfect.

I don't favor uranium enrichment, for instance, and would rather recover the energy potential of U-238 via the U-233 dilution process with natural or once, twice, x times through uranium.

Any residual Cl-35 that is not removed will capture neutrons to give Cl-36, which has a half life of 310,000 years, and very little to recommend itself as an item of commerce.

Thus it will have, most likely, to be dumped ultimately. There are very few insoluble chlorides. Silver is one, mercury (I) another. Silver chloride is subject to photochemical dissociation and mercury I chloride is subject to oxidation under the right circumstances.

I like fast reactors. I think it is absolutely essential that we have fast reactors as part of our nuclear fleet, because I like plutonium which is not to say that I dislike thorium/U-233.

I am a big fan of fluid phase reactors. But I don't think that chloride is the only route to fluid phase fast reactors.


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PostPosted: Jul 31, 2010 1:42 am 
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NNadir wrote:
The universe does not live by one set of anions alone, however, and were we to so choose, we could move beyond the halogens.


That's a nice cryptic statement 8) but could you be more specific? O, C, N have been used in solid fuels, with oxide fuels being the most common today. B is probably suitable for this purpose as well (if enriched boron). But these are all solid fuels. P and S have numerous problems ranging from viscosity to melting point to reprocessing issues etc. On the right hand of the periodic table we have the noble gasses, which are, well, noble. What chemistry are you thinking about?


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PostPosted: Jul 31, 2010 10:03 am 
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Hmm, I just checked the nndc x-sections database and while bromine and iodine don't look too good in fast spectrum in terms of total cross sections it seems that they at least shouldn't have bad resonance problems. In fact it looks like it is chlorine that has bad resonances over the entire fast spectrum - even pure chlorine 37 has some serious peaks above epithermal.

Bromine and iodine don't have resonances as long as you stay above epithermal (10-20 keV or so). In fact the total cross sections are not much worse than sodium, the most common coolant for solid fueled fast reactors. I think the real problem will be the inelastic scattering x-section, similar to the issue discussed recently regarding fast fluoride reactors. Chlorine-37 is really excellent here.


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PostPosted: Aug 01, 2010 7:38 pm 
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NNadir wrote:
dezakin wrote:
NNadir wrote:
The best halogen, the only halogen that I see as acceptable, however is fluorine. I'm not a fan of molten chloride reactors.

Why not? Neutron spectrum or chemical issues? While I find chloride salt reactors far less mature than fluoride reactors, the amazing neutron budget is kinda interesting.


Cl-37 has good neutron properties, I confess, but Cl-35 is not great.

Chloride reactor fans of course say, "separate the isotopes." This is possible of course, and would work, but I ask, why bother?

We have to do the same thing with FLiBe with lithium, though the mass difference might be large enough to do some less expensive isotopic separation at that level...

Quote:
In general, with the exception of deuterium, because of its huge isotope effect, isotopic separations are economically and often energetically troublesome and imperfect.

I don't favor uranium enrichment, for instance, and would rather recover the energy potential of U-238 via the U-233 dilution process with natural or once, twice, x times through uranium.

Any residual Cl-35 that is not removed will capture neutrons to give Cl-36, which has a half life of 310,000 years, and very little to recommend itself as an item of commerce.

Thus it will have, most likely, to be dumped ultimately.

When? Why? You have enriched chlorine and now its mildly radioactive, which would be fine if you're running fast reactor regimes because you're just going to use it in another reactor.


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PostPosted: Aug 02, 2010 10:17 am 
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NNadir wrote:
dezakin wrote:
NNadir wrote:
The best halogen, the only halogen that I see as acceptable, however is fluorine. I'm not a fan of molten chloride reactors.

Why not? Neutron spectrum or chemical issues? While I find chloride salt reactors far less mature than fluoride reactors, the amazing neutron budget is kinda interesting.


Cl-37 has good neutron properties, I confess, but Cl-35 is not great.

Chloride reactor fans of course say, "separate the isotopes." This is possible of course, and would work, but I ask, why bother?

In general, with the exception of deuterium, because of its huge isotope effect, isotopic separations are economically and often energetically troublesome and imperfect.

I don't favor uranium enrichment, for instance, and would rather recover the energy potential of U-238 via the U-233 dilution process with natural or once, twice, x times through uranium.

Any residual Cl-35 that is not removed will capture neutrons to give Cl-36, which has a half life of 310,000 years, and very little to recommend itself as an item of commerce.

Thus it will have, most likely, to be dumped ultimately. There are very few insoluble chlorides. Silver is one, mercury (I) another. Silver chloride is subject to photochemical dissociation and mercury I chloride is subject to oxidation under the right circumstances.

I like fast reactors. I think it is absolutely essential that we have fast reactors as part of our nuclear fleet, because I like plutonium which is not to say that I dislike thorium/U-233.

I am a big fan of fluid phase reactors. But I don't think that chloride is the only route to fluid phase fast reactors.

I agree with you about fluid fuel reactors. I am also a big fan of fast reactors but not of the usual sodium coolant. That takes us to lead based fuel solutions. The document repository has a few papers on graphite moderated fluid metal fuel reactors but not on fast reactors. A fluid fuel version of Russian SVBR-100 seems just what the doctor ordered. Like all fluid fueled reactors, fuel changes are easy. We could start with the actinides and part of unspent uranium in the nuclear fuel "waste" and proceed to a thorium cycle. 20%LEU is also an optional starting option.


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PostPosted: Aug 02, 2010 12:22 pm 
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jagdish wrote:

...

I agree with you about fluid fuel reactors. I am also a big fan of fast reactors but not of the usual sodium coolant. That takes us to lead based fuel solutions. The document repository has a few papers on graphite moderated fluid metal fuel reactors but not on fast reactors. A fluid fuel version of Russian SVBR-100 seems just what the doctor ordered. Like all fluid fueled reactors, fuel changes are easy. We could start with the actinides and part of unspent uranium in the nuclear fuel "waste" and proceed to a thorium cycle. 20%LEU is also an optional starting option.

The problem with liquid metal fuel is solubility limits. IIRC, the maximum attainable uranium concentration is still too low for a fast reactor. That's why it's graphite moderated.


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