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PostPosted: Mar 11, 2009 1:19 am 
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While on fast spectrum reactors, here is my post on another thread:-
Further thinking on possibilities of a calandria configuration brought into focus an entirely new concept-
A Liquid Metal Reactor

Liquid Fluoride Thorium Reactor (LFTR) is being discussed for utilisation of thorium fuel. In India, metallic fuel is being researched for fast reactors to produce more 233U for thorium fuelled reactors. Some characteristics of both could be used in the design of a Liquid Metal Reactor.
The liquid part of its name shall be based on liquid lead. The lead has a melting point of 327C, comparable to molten salt eutectics and it has been used as a coolant in fast reactors. It also stops Gamma Rays but does not absorb too many neutrons. Its nuclei are too heavy to slow down neutrons. The melting point shall go down somewhat further due to dissolved fuel. The fluid fuel, consisting of thorium and fissile feed dissolved in lead, shall be liquid over a large range including operating temperatures. A suitable ceramic coating can be provided to reactor vessel to counter the corroding effect of lead.
The neutron spectrum shall be fast as expected from a metallic fuel with no moderation. The high conversion/breeding ratio shall partly offset the neutron loss to fission products in liquid metal resulting in high burn up. More volatile fission products including Xe, Kr and Iodine shall be converted to vapour and removed from the core.
In parallel with molten salt reactors (including LFTR) any increase in temperature shall result in some expansion of the fuel and have a balancing effect through reduced reactivity. The vessel may be divided in to sections to enable change of fuel in one section at a time. The unloaded fuel can be refined for removal of dissolved fission products, and brought back to original composition at an onsite facility and fed back during the next change. Additional thorium can be added to make up fission losses. Excess U-233 produced can be stored for next reactor.
The concept occurred to me when thinking of further possibilities of calandria. In fact all it has in common with LFTR is the fluid fuel. All configurations of fluid fuel are possible.
Let experts give their views on this concept.


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PostPosted: May 26, 2009 5:06 pm 
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Alex P wrote:
Alex P wrote:
Intersting enough, the reactor achieves a breeding gain of 0,25 even without chlorine enrichment, absolutely higher than that experienced at Superfenix sodium fast reactor (very curious what that number can become with chlorine enrchment!)


Forgot to mention that in a chloride fast reactor with a thorium blanket the 0,25 breeding gain cited is very likely not achievable at all, a non-negligible fact


Oh, my! I realize only now that the real breeding is only 0,03, not 0,25 as I previously stated....I grossly confused the numbers, gosh ! :oops:

All the more so, without chlorine enrichment, is even more difficult to reach breeding considering rather a thorium (not DU) blanket. However, if I understand correctly, assuming we can achieve at least a breeding gain = zero even with the thorium cycle, considering the high fissile inventory cited - 4,9 tonn of TRUs per GW thermal - I think it is not particurally difficult to produce several tens of tonns of U-233 from a single GWe of LCFR in few years, able to start up to 60 or 70 GWe of liquid fluoride thorium reactors, even in the neutron economy poorer moderator free, epithermal version (needing at max less than 1000 kg per GWe of start up fissile).

Besides this, are there for liquid chlorides fast reactors other particular issues in terms of corrosion or material R&D vs liquid fluorides reactors technology?


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PostPosted: Jun 14, 2009 4:25 am 
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Luke wrote:
Chlorine enrichment may not be too hard - Kirk has a (translated) Russian paper Chlorine Isotope Separation by Liquid-Phase Thermal Diffusion in the archives giving one method for doing it - but it's not an established large-scale process either, and is bound to be an added cost. Whether or not to do it is one of the many things that would have to be investigated by an R&D effort on chloride reactors.Luke

CCl4 mentioned in the paper is a poor starting point for isotope seoeration. 4 Cl atoms in a molecule would be a combination of Cl35 and Cl37 in any proportion. It would be far better to start with a gas with one Cl atom like HCl or CH3Cl. Separation of Li7 isotope (92.5%) could, however be as problematic or easy as isotope Cl37 (24.3%).


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PostPosted: Jun 14, 2009 5:56 pm 
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jagdish wrote:
Luke wrote:
Chlorine enrichment may not be too hard - Kirk has a (translated) Russian paper Chlorine Isotope Separation by Liquid-Phase Thermal Diffusion in the archives giving one method for doing it

CCl4 mentioned in the paper is a poor starting point for isotope seoeration. 4 Cl atoms in a molecule would be a combination of Cl35 and Cl37 in any proportion. It would be far better to start with a gas with one Cl atom like HCl or CH3Cl. Separation of Li7 isotope (92.5%) could, however be as problematic or easy as isotope Cl37 (24.3%).

The authors show in the paper that CCl4 undergoes Cl exchange on a reasonably fast timescale, so although C(37Cl)4 is only 0.35% of natural CCl4, as the separation pulls out the C(35Cl)4 and C(35Cl)3(37Cl) the population distribution of the rest adjusts, allowing all the 37Cl to be recovered at any desired purity, given enough stages.
Gas centrifuge separation of HCl, or perhaps MeCl to avoid the corrosion issues of HCl is a more obvious route, but building and operating a centrifuge train is an expensive business.

Luke


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PostPosted: Jan 08, 2010 11:48 am 
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jagdish wrote:
While on fast spectrum reactors, here is my post on another thread:-
Further thinking on possibilities of a calandria configuration brought into focus an entirely new concept-
A Liquid Metal Reactor

Liquid Fluoride Thorium Reactor (LFTR) is being discussed for utilisation of thorium fuel. In India, metallic fuel is being researched for fast reactors to produce more 233U for thorium fuelled reactors. Some characteristics of both could be used in the design of a Liquid Metal Reactor.
The liquid part of its name shall be based on liquid lead. The lead has a melting point of 327C, comparable to molten salt eutectics and it has been used as a coolant in fast reactors. It also stops Gamma Rays but does not absorb too many neutrons. Its nuclei are too heavy to slow down neutrons. The melting point shall go down somewhat further due to dissolved fuel. The fluid fuel, consisting of thorium and fissile feed dissolved in lead, shall be liquid over a large range including operating temperatures. A suitable ceramic coating can be provided to reactor vessel to counter the corroding effect of lead.
The neutron spectrum shall be fast as expected from a metallic fuel with no moderation. The high conversion/breeding ratio shall partly offset the neutron loss to fission products in liquid metal resulting in high burn up. More volatile fission products including Xe, Kr and Iodine shall be converted to vapour and removed from the core.
In parallel with molten salt reactors (including LFTR) any increase in temperature shall result in some expansion of the fuel and have a balancing effect through reduced reactivity. The vessel may be divided in to sections to enable change of fuel in one section at a time. The unloaded fuel can be refined for removal of dissolved fission products, and brought back to original composition at an onsite facility and fed back during the next change. Additional thorium can be added to make up fission losses. Excess U-233 produced can be stored for next reactor.
The concept occurred to me when thinking of further possibilities of calandria. In fact all it has in common with LFTR is the fluid fuel. All configurations of fluid fuel are possible.
Let experts give their views on this concept.

Liquid metal reactors were considered by the US AEC in the late 1950's, but were determined to have less potential than MSRs. It might be a good idea to review the AEC discussion on the issue.


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PostPosted: Jan 09, 2010 1:19 am 
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Liquid metal reactor papers I have seen so far were attempts to create thermal reactors. Lead-Bismuth solvent-coolant could be a better option for fast spectrum fluid fuel reactors. The material has been used as a coolant for fast reactors and is also proposed for SVBR-100.
http://www.gidropress.podolsk.ru/English/razrab_e.html


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PostPosted: Nov 30, 2010 4:58 am 
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Alex P wrote:
Potentialities of the fast spectrum molten salt reactor concept : REBUS-3700
http://cat.inist.fr/?aModele=afficheN&cpsidt=17946152

Abstract :
"...a description of the system design, as well as a justification of its operating parameters is given. The performed neutronics studies demonstrate that REBUS-3700 gathers a positive breeding gain and strong negative salt expansion reactivity feedback. The safety analysis demonstrates an excellent reactor behavior with respect to the majority of single and combined unprotected events"

Have you got the full paper? Do you know anything more?

Please find a copy attached, it reads pretty well, quite amazing performance, but has some significant gaps around materials suitable for construction. From a fuel cycle perspective it sounds very promising albeit some distance behind fluoride salt based reactor technologies. Definitely worth a read.


Attachments:
Rebus 3700.pdf [235.63 KiB]
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PostPosted: Nov 30, 2010 3:14 pm 
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Thanks Linsday, unfortunaletly (or not) this thread it's very old, I already found and read a such copy.

Maybe now it's time to discuss about the possibility of a single chloride DMSR, like the well know fluoride DMSR cousin...


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PostPosted: Dec 01, 2010 1:31 am 
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A denatured chloride reactor?
I don't think this makes sense for uranium 233 or 235 since the denaturing means we need to go thermal to achieve criticality. If you are thermal then why fuss with chloride for uranium.

Otherwise, we could talk a plutonium machine and using chloride for the extra solubility. But we don't normally talk about denatured plutonium. The only denaturant for plutonium is 238Pu and so far the definition is 80% 238Pu (grandfathered in based I presume on what the thermal generators use rather than any theoretical weapon that could be contrived by the best of the best).


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PostPosted: Dec 01, 2010 7:32 am 
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A Molten Chloride Thorium Fast Reactor is a desirable end to follow. A neat ThCl4-233UCl4 liquid fuel, with or without a liquidizing salt may be used. MgCl2 or a eutectic with NaCl will be lower melting. 233UCl4 as a fissile component has a BP of 791C and may add to self regulation by turning into vapor.
If the starting fissile feed is 20% LEU, some Thorium salt can be added to adjust enrichment which will also convert it into a DMSR.
Isotope Cl37("Heavy Chlorine") is useful for neutron efficiency and may be necessary for avoiding repeated fissile feed.


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PostPosted: Dec 01, 2010 9:04 am 
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Lars wrote:
A denatured chloride reactor?
I don't think this makes sense for uranium 233 or 235 since the denaturing means we need to go thermal to achieve criticality. If you are thermal then why fuss with chloride for uranium.

Otherwise, we could talk a plutonium machine and using chloride for the extra solubility. But we don't normally talk about denatured plutonium. The only denaturant for plutonium is 238Pu and so far the definition is 80% 238Pu (grandfathered in based I presume on what the thermal generators use rather than any theoretical weapon that could be contrived by the best of the best).


I think he’s talking about the concept we discussed previously, start up a single fluid chloride once through without online fuel processing, using spent nuclear fuel transuraniums but transitioning to thorium by using thorium as the dominant fertile. Put in some U238 for initial denaturing so the initial bred U233 is not misused – possibly this step can be avoided altogether as there is simply no plausible means on site to remove fissile. Bulk salt removal is just not plausible, even after 1 month the stuff will be dangerously radioactive and it is not easy to remove uranium using kitchen equipment!

No need to add any fissile top up, so no need for denaturing there in the first place. Fill 'r up 'n go!

One cool thing is that NaCl PuCl3 UCl3 UCl4 ThCl4 have very low melting eutectics with large actinide loadings, and infinite mutual solubilities.


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PostPosted: Dec 01, 2010 8:00 pm 
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Cyril, I'm glad that you found that paper ok, have you come across any other papers talking about the Rebus 3700, I've found precisely 1, Pavel Bokov's Phd thesis on MSR safety studies, but I'd be keen to locate others.

Regarding molten chloride fast reactors (MCFR's), I don't see much space for them as rival to DMSR. The reason that I say that is the ease with which they could be adapted to breed Pu239 from U238, there are so many spare neutrons that to me at least they pose a serious proliferation risk, which in turn dictates they the should be used in fully secured and regulated environments only.

One other feature, and I might get excommunicated for this, but if you look at the numbers at a high level, there is no need to burn Th in MCFR's. They are well suited to burning depleted uranium (DU) or better still spent nuclear fuel. If a Rebus 3700 burns 1t of DU per GWe per year in rough numbers, the world is digging up say 50,000 t of uranium a year. If we imagine that 46,000 t/y is available as DU or SNF, that could support 46,000 GWe or 342,751 TWh/year.

At the moment the world is only consuming something like 17 - 19,000 TWh/year, so it looks like there is any amount of DU or SNF to go around for a very long time. I know it sounds bizarre, but those are the numbers I get for a DU/SNF fuelled MCFR system.


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PostPosted: Dec 01, 2010 10:26 pm 
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I agree that in a fast spectrum 238U looks like a better fertile feed than 232Th. I would also agree that the number of fast chloride machines will be small - likely used to eliminate TRUs from LFTRs.

For volume power production I think LFTR is better than fast chloride. It doesn't matter whether the fertile is 238U (from SNF/U or DU or natural U) or thorium. The amount of fuel required is too small to worry about anyway.


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PostPosted: Dec 02, 2010 4:57 am 
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It is important to stress the purpose of my chloride DMSR idea. The purpose is to convert SNF TRU to U233 without the development need and cost for online fuel processing. That also means that any Pu239 bred from the U233 initial denaturant U238 cannot be easily removed, and even if it is removed you get all the poor quality startup Pu out. Thus, misuse requires startup on mined U and you need more of that with a fast reactor so its harder than a thermal reactor. Remember all Pu239 for weapons has been made in thermal reactors…

There is another point and that is TRU creation. If you process online with a HUGE TRU inventory (eg starting up a fast chloride reactor on predominantly TRU) that means you have more TRU going to waste.

We are not talking two fluid here. Besides proliferation I am not convinced that the barrier has a reasonable enough lifetime. Its just easier to make the reactor a big one with low power density. Reduces losses with plausibly acceptable materials requirements.


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PostPosted: Dec 02, 2010 12:55 pm 
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I'm not clear on the idea yet - here is what I understand.
Single fluid, chloride salt, fed with SNF/TRUs.
Producing 233U so presumably lots of thorium in the fuel salt.
Denatured - so enough 238U to denature the produced 233U.
Fast spectrum.


For criticality we need to be sure that for every fission one of the generated neutrons causes a fission. This limits the ratio of fertile to fissile (too much fertile and you absorb too many neutrons in the fertile not leaving enough for the next generation of fission).

SNF/TRU is not all fissile so that absorbs much of your neutron budget and means you don't get to put in bunches of fertile.

Denaturing the 233U means we need 7x as much 238U as 233U.
If there is much 233U compared to 239Pu then you will not have any neutron budget left to add the thorium.

So, I'm thinking such a machine would need to pull out the uranium on a pretty rapid basis (say a 6 month time to process all the salt). This isn't hard, but when you pull out the uranium you will pull out both the 238U and the 233U. So you will need to periodically add 238U to keep the reactor denatured.

The operators of such a machine could be easily replace the 238U addition with thorium and thus produce 233U (+232U). Or they could just take the SNF/Pu. So the denaturing feature here isn't really for the risks associated with operating the machine itself but rather to reduce the risks during shipment from this machine to other machines.


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