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PostPosted: Aug 06, 2009 7:52 am 
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Hi folks,

Yesterday I had the pleasure to visit Dr. Jan Uhlir and his group of molten fluoride salt chemistry at Rez. I was quite awestruck by the depth and scope of the projects, in contrast of what is known about it. Is is the only place in the world which integrates theoretical nuclear reactor research, practical reactor experiments, with theoretical and experimental molten salt chemistry. The nuclear engineering department at Czech Technical University started a semester course on fluid nuclear fuels several years ago, also a rarity these days.

The molten salt research there dates back to 60s and 70s. The pilot technological line FREGAT-2 was build it mid 70s, for fluoride reprocessing SNF from fast spectrum reactors. Some historic details are in this 1998 paper: http://www.nea.fr/html/trw/docs/mol98/s ... paper9.pdf

The research continued throughout the 90s following the interest in accelerator-driven systems, then people realized it does not add up. However the idea of MSR is still sound, accelerator or not, so the research continues aimed at LWR waste utilization, and Th cycle.

I saw ThF4 (white grains) and salt with dissolved uranium (a nice green slug - MSR is a green energy for real :) ), glove-boxes for electro-refining of the molten salts, an experimental line FERDA, and met about 5 of the young members of the chemistry group. A recent talk by Dr. Uhlir about the MSR R&D efforts with the description of the FERDA line: http://www.nea.fr/html/pt/iempt10/prese ... 9Uhlir.pdf

I saw stack of recent Bc. Msc. and PhD thesis on the topics related to MSR. I also saw a piece of a new steel alloy MoNiCr, a modern version of Hastelloy-N developed by Skoda. (Details on MiNoCr steel composition can be found here). I was given a paper on their 2-fluid design with doubling time of 2.6 years (!) presented at ICAPP09: Neutronic Analysis of Two-Fluid Thorium Molten Salt Reactor J. Frybort, R. Vocka (NRI).

Next week I will come for another visit, to see their MS test loop in the LVR-15 research reactor next door. I very much recommend to visit the place, as part of your work travel or vacation in Europe. The besides the science, the nature around the institute is wonderful.


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PostPosted: Aug 06, 2009 8:35 am 
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Excellent trip report! I hope you conveyed my best wishes to Dr. Uhlir--I really enjoyed meeting him in Atlanta and hope to get out to Rez one of these days!


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PostPosted: Aug 06, 2009 11:28 am 
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ondrejch wrote:
I was given a paper on their 2-fluid design with doubling time of 2.6 years (!) presented at ICAPP09: Neutronic Analysis of Two-Fluid Thorium Molten Salt Reactor J. Frybort, R. Vocka


Wow! 2.6 years! That's incredible. How do they manage it?


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PostPosted: Aug 06, 2009 12:46 pm 
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honzik wrote:
ondrejch wrote:
I was given a paper on their 2-fluid design with doubling time of 2.6 years (!) presented at ICAPP09: Neutronic Analysis of Two-Fluid Thorium Molten Salt Reactor J. Frybort, R. Vocka
Wow! 2.6 years! That's incredible. How do they manage it?

Clever 2 fluid core design with 240 tubular graphite channels, most of them with an inner bore of 3cm in radius with fuel salt, 3cm thick wall; surrounded by 0.4cm blanket salt annulus; total radius of the channel is 8cm. The channels are 4m long. 2500 MWt - the reference design is ORNL-4528. They do extract Pa. Feedback -9.53 pcm/K. Fuel salt speed 2.4 m/s. They do acknowledge that the parameters are ideal, assuming ideal reprocessing.

The paper is a proceeding from ICAPP09, and I guess it can be obtained either from Dr. Uhlir, or from one of the authors, Jan Frybort, frb<at>ujv.cz (Google does not seem to have a copy (yet)).


Last edited by ondrejch on Aug 13, 2009 10:50 pm, edited 2 times in total.

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PostPosted: Aug 06, 2009 3:56 pm 
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ondrejch wrote:
The channels are 4m long. 2500 MWt - the reference design is ORNL-3913. They do extract Pa. Feedback -9.53 pcm/K. Fuel salt speed 2.4 m/s.


That is very nice.


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PostPosted: Aug 06, 2009 4:01 pm 
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USPWR_RO wrote:
ondrejch wrote:
The channels are 4m long. 2500 MWt - the reference design is ORNL-3913. They do extract Pa. Feedback -9.53 pcm/K. Fuel salt speed 2.4 m/s.


That is very nice.


That's the kind of beautiful performance you can get from a two-fluid reactor.


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PostPosted: Aug 06, 2009 4:12 pm 
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USPWR_RO wrote:
ondrejch wrote:
The channels are 4m long. 2500 MWt - the reference design is ORNL-3913. They do extract Pa. Feedback -9.53 pcm/K.


That is very nice.


This is also very costly!

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PostPosted: Aug 07, 2009 2:11 pm 
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Ondreji,

Does it look like the group at REZ has any plans to build an experimental MSR in the near future? They've been working on the infrastructure for a while, but I haven't seen any concrete plans for a fully functional test reactor. It sure would be nice if they could get a smaller version (~50 MWt) of their breeder reactor up and running. Do they have a sufficient depth in the design experience to pull this off, or would they have to team up with groups in other countries (Russia, France, etc.)?


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PostPosted: Aug 08, 2009 10:26 pm 
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Here is a very interesting paper summarizing the experimental efforts, attached:

Reactor Physical Experimental Program EROS in the frame of the Molten Salt applying Reactor Concepts Development
Miloslav Hron, Jan Kyncl, Miroslav Mikisek
NUCLEAR RESEARCH INSTITUTE REZ PLC,
Husinec – Rez 130, 250 68 Rez, Czech Republic


Attachments:
File comment: Reactor Physical Experimental Program EROS in the frame of the Molten Salt applying Reactor Concepts Development
Miloslav Hron, Jan Kyncl, Miroslav Mikisek

Hron9233.pdf [445.08 KiB]
Downloaded 263 times
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PostPosted: Aug 10, 2009 3:08 pm 
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Here's another presentation entitled Comparison of Electricity Production from the Nuclear Energy and from the Renewable Energy Sources, from researchers from the NRI. Be sure to check out the chart of total CO2 emissions on page 17 and total waste on page 19. Nuclear in both cases is very favorable compared to other technologies...


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PostPosted: Aug 10, 2009 10:02 pm 
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Quote:
Feedback is -9.53 pcm/K.
I've been out of class too long. Can you expand that phrase for me?

Is that the temperature sensitivity of the reactor, dk/dT?

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PostPosted: Aug 11, 2009 1:37 am 
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Jumping in headfirst with both feet firmly in mouth, I think that's how much the reactivity changes per C degree increase in fuel temperature. pcm stands for percent-milli (so I think thats parts per hundred thousand).

The practical effect - fuel get hot, handbrake goes on and reaction slows waaay down.

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PostPosted: Aug 11, 2009 3:40 am 
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Leviathan wrote:
Quote:
Feedback is -9.53 pcm/K.
Is that the temperature sensitivity of the reactor, dk/dT?
Yes.


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PostPosted: Aug 13, 2009 1:50 pm 
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ondrejch wrote:
honzik wrote:
ondrejch wrote:
I was given a paper on their 2-fluid design with doubling time of 2.6 years (!) presented at ICAPP09: Neutronic Analysis of Two-Fluid Thorium Molten Salt Reactor J. Frybort, R. Vocka
Wow! 2.6 years! That's incredible. How do they manage it?

Clever 2 fluid core design with 240 tubular graphite channels, most of them with an inner bore of 3cm in radius with fuel salt, 3cm thick wall; surrounded by 0.4cm blanket salt annulus; total radius of the channel is 8cm. The channels are 4m long. 2500 MWt - the reference design is ORNL-3913. They do extract Pa. Feedback -9.53 pcm/K. Fuel salt speed 2.4 m/s. They do acknowledge that the parameters are ideal, assuming ideal reprocessing.

The paper is a proceeding from ICAPP09, and I guess it can be obtained either from Dr. Uhlir, or from one of the authors, Jan Frybort, frb<at>ujv.cz (Google does not seem to have a copy (yet)).


Is that the right report # ORNL 3913? That report is a collection of chemistry papers. I'm just curious as I've never seen Oak Ridge quote as low as 2.6 years even for their Two Fluid work. I assume they were talking about ORNL's Two Fluid design of interlacing fuel and blanket salts which evolved but remained about the same from 1965 or so to 1968. I guess that depends on what they assume is "ideal reprocessing", maybe they are also assuming lower starting inventories.

The "plumbing problems" of interlacing fuel and blanket salts within the core is probably still nearly insurmountable if for no other reason than the shrinking and expanding graphite tends to dramatically change the ratio of the two fluids within the core (and the work on using metal looked even more hopeless). Hopefully we can convince them of the merits of a new simple geometry of tube within tube that only needs one barrier, not thousands. The old ORNL Two Fluid design also has a positive temperature reactivity coefficient for the blanket salt which they rarely mentioned. If your blanket salt is only surrounding a core of fuel salt, it ends up to also have a negative temp coefficient since it acts as a reflector (hotter=less dense=less neutrons reflected back)

David L.


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PostPosted: Aug 13, 2009 2:52 pm 
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I don't want to shoot the messenger but this seems too good to be true.

I would be interested in seeing how one gets to a doubling time of 2.6 years.


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