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PostPosted: Sep 21, 2015 3:34 pm 
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For the past couple months I've been working on a paper which points out why US NE decision makers should focus their R&D people/resources upon the development of MSR-type isobreeders, not "NGNP's" & SMRs. The first of them would be a optimized version of EVOL's fluoride salt-based Th breeder that I've described earlier this year (http://onlinelibrary.wiley.com/doi/10.1002/ese3.59/full). The second would be a no-blanket version of the chloride salt, U/Pu-based, MCFR. Up until three days ago I was stuck on the latter concept because no one I'd asked to do so (including people at the INL and the faculty of several of this county's more prominent academic NE departments) had volunteered to do the absolutely necessary "modern" neutronics modeling (I'm just a chemist).

That's now history because Ondrej Chvala has volunteered to do it. We haven't yet decided upon exactly what we're going to be proposing (i.e., the numbers in the ATTACHMENT's Fig 8 - one thing we do know for sure is that the reactor will have to be considerably bigger - roughly 80-100 m3 of fuel salt instead of 25), but it's now clear that the concept is viable.

Please look over the ATTACHED "work in progress" & get back to me/us with your comments/advice.


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MCFR & MSFR paper-post chvala mods.doc [1.47 MiB]
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PostPosted: Sep 22, 2015 12:55 pm 
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Darryl,
The term "iso-breeder" sounds so nasty. How about using the term "sustainer" instead. It contains a term the faux-greens like as much as the real greens.

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PostPosted: Sep 22, 2015 3:57 pm 
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KitemanSA wrote:
Darryl,
The term "iso-breeder" sounds so nasty. How about using the term "sustainer" instead. It contains a term the faux-greens like as much as the real greens.



I don't like the nuclear industry's compulsion to substitute "non emotive" words/terms (i.e., "events" for bomb blasts) & acronyms for more descriptive/accurate labels - most "outsiders" don't either. "Isobreeder" is a perfectly good term -we don't need another.

Here's an update to the paper which includes some specifics about the blanketless MCFR concept - (it's still a work in progress).


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PostPosted: Sep 23, 2015 1:00 pm 
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macpacheco wrote:

I second that. Nuclear will always... .


Thanks much.

Here's the "final" version of the paper. I've decided to send it off to SCIENCE just for the fun of it. I don't really expect it to be accepted because it's apt to rub too many "important" people the wrong way.


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PostPosted: Sep 23, 2015 6:14 pm 
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That is fine. But to those who want to talk to regular people, they will understand "sustainer" and feel better about it than "iso-breeder". Just a thought.

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PostPosted: Sep 24, 2015 12:53 am 
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Total fissile available from mined uranium is 0.7% of uranium and nearly 0.15% of U plus Th. There are large stocks of depleted uranium too, in addition to mused fuel, called 'waste' problem. The fissile feed required is much higher. Therefore breeding is necessary for a cycle not leaving problem used fuel as is the case with present day thermal reactors. Blanket is a very desirable feature in a reactor design.
The best blanket option, as far as I can understand, is metallic thorium which can be electro-refined after optimum irradiation.


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PostPosted: Sep 27, 2015 1:19 pm 
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Dear Jagdish

from my point of view there is a high neutron flux at the edges of any fast nuclear reactor that needs to be reflected or absorbed. A blanket or fertile zone is the ideal reflector/absorber for these neutrons as they are used for something useful. If there is a real surplus of fissionable material it can be sold as fuel for LWR or other reactors. If nuclear should develop beyond large reactors for base load electricity generation once there will be plenty of small reactors with a breeding rate < 1* required.

The non-proliferation idea is a strange idea generated by the Carter administration in the US. Countries like the US, Russia, China, UK and France have a surplus of fissionable material anyway. It doesn`t make sense for them. Countries like Japan, South Korea, Taiwan, Sweden, Switzerland have a sufficient technology to make nice gadgets without their commercial reactors. Other countries like North Korea do not care about such considerations.


*A very interesting reactor concept is the russian SVBR75/100. It could be used to power large container ships, crude tankers... on their routes around the globe. It could as well used to power mines far away from the electricity grid. Its breeding is < 1.


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PostPosted: Sep 27, 2015 11:56 pm 
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I agree that there is a niche for fast reactors with CR<1. Breeders are a requirement to keep used fuel stocks down and to reduce mining.


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PostPosted: Sep 28, 2015 2:47 pm 
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From your note 18,
Quote:
From a reactor neutronics standpoint, sodium is less desirable than is pure 7Li because its higher parasitic neutron absorption cross section tends to suppress breeding and require a higher fissile concentration.

Is that really true ?
Can you illustrate please ?
From my sources, it appears that Na23 is better than Li7 in a fast spectrum.
Thanks.


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PostPosted: Sep 28, 2015 2:57 pm 
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The paper talks only about "natural NaCl salt", whereas other proposals (ex. Moltex MCFR) adopt isotopically separated Cl37 salt.
The reaction Cl35(n,p)S35 has quite a large x-section in the fast spectrum (four orders of magnitude higher than Na23(n,g)Na24 ).
Why is this issue not mentioned ?
Is it not a concern ?
Thnx.


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PostPosted: Sep 28, 2015 10:50 pm 
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jaro wrote:
From your note 18,
Quote:
From a reactor neutronics standpoint, sodium is less desirable than is pure 7Li because its higher parasitic neutron absorption cross section tends to suppress breeding and require a higher fissile concentration.

Is that really true ?
Can you illustrate please ?
From my sources, it appears that Na23 is better than Li7 in a fast spectrum.
Thanks.


2Na is "better" because it's much cheaper, a poorer moderator (lighter atom), doesn't produce nearly as much tritium, and its n,gamma absorption is low enough to not seriously inhibit breeding.

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PostPosted: Sep 28, 2015 11:03 pm 
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jaro wrote:
The paper talks only about "natural NaCl salt", whereas other proposals (ex. Moltex MCFR) adopt isotopically separated Cl37 salt.
The reaction Cl35(n,p)S35 has quite a large x-section in the fast spectrum (four orders of magnitude higher than Na23(n,g)Na24 ).
Why is this issue not mentioned ?
Is it not a concern ?
Thnx.


I'm not "concerned" but it would probably be worthwhile to find out how much it would cost to make/use pure 37Cl instead. If this fuel cycle is properly implemented (i.e., with chlorine recycle) it'd just be a one-time cost.

One possibility that hasn't discussed as far as I know is that most of any such sulfur might end up forming sulfides with FPs & thereby not compromise the reactor's tank, pipes, or HX.

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PostPosted: Sep 29, 2015 12:59 am 
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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.


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PostPosted: Sep 29, 2015 9:01 am 
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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.

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PostPosted: Sep 29, 2015 11:55 am 
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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


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