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PostPosted: Dec 20, 2014 9:38 am 
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https://inlportal.inl.gov/portal/server ... =DA_636199

Here is an article on testing silicon carbide-based cladding and other cladding materials.

Can there be some benefit to a LFTR using this to protect the reactor vessel from damage?


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PostPosted: Dec 20, 2014 1:43 pm 
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...Or maybe as fuel channel plumbing for a D2O-moderated molten salt reactor?


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PostPosted: Dec 20, 2014 3:22 pm 
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Ida-Russkie wrote:
https://inlportal.inl.gov/portal/server.pt/community/newsroom/257/feature_story_details/1269?featurestory=DA_636199

Here is an article on testing silicon carbide-based cladding and other cladding materials.

The link doesn't work for me. Does it work for others here ? (Thnx)


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PostPosted: Dec 20, 2014 3:26 pm 
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Titanium48 wrote:
...Or maybe as fuel channel plumbing for a D2O-moderated molten salt reactor?

Transatomic said recently that they want to use it for the tubes holding the ZrH moderator.

This means they abandoned their original plan to use Hastelloy tubing (bad for neutron economy) -- as well as their stated intent to use only proven materials.


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PostPosted: Dec 21, 2014 11:41 am 
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That's a great new. SiC seems compatible with molten salts, lead and hot water (someone corrects me if I am wrong). They plan to use it for Gas Fast Reactors too and of course it is already used in triso particules. So SiC based materials seem to be very critical components for the entire nuclear industry. I wonder why there is not more research on the subject. The downsides are the difficulties and the cost of manufacturing.


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PostPosted: Dec 21, 2014 11:55 am 
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I think the jury's still out with regards to SiC compatibility in fluoride salts.


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PostPosted: Dec 21, 2014 12:03 pm 
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Wasn't there a presentation at TEAC two years ago that basicaly said it was INcompatible?

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PostPosted: Dec 21, 2014 12:29 pm 
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I am sorry, I saw several times papers with SiC used in MSRs concepts so I thought it was compatible. I will look more at this subject.


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PostPosted: Dec 21, 2014 11:33 pm 
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I found one of the papers that I had seen, it speaks about corrosion tests in Flibe :

http://www.iaea.org/NuclearPower/Downloadable/Meetings/2014/2014-06-10-06-13-TM-NPTD/6_Sridharan_USA__IAEA_Presentation_June_2014.pdf

I am very bad in corrosion but It seems in this paper that CVD SiC is highly resistant to corrosion in clean Flibe or I don't understand the paper. Even the other types of SiC seem good. Maybe chemical vapor deposition is too costly or difficult.


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PostPosted: Dec 22, 2014 6:17 pm 
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The difference between CVD and CVI in this case is mostly to do with stoichiometry. CVI tends to leave free silicon, which is active in a fluoride melt. SiC with one silicon per carbon and everything bound up neatly is very inert in clean FLiBe, though fuel salt remains to be seen. In case of the Transatomic reactor there is also free hydrogen and hydride on the inside as well as fuel salt on the outside of cladding. Very different than pure FLiBe.

Whats the latest on the MIT triplex SiC cladding for PWRs? They were doing live reactor tests as I recall. They should know the effect of fission products at least.


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PostPosted: Dec 23, 2014 7:59 am 
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fab wrote:
I found one of the papers that I had seen, it speaks about corrosion tests in Flibe :

http://www.iaea.org/NuclearPower/Downloadable/Meetings/2014/2014-06-10-06-13-TM-NPTD/6_Sridharan_USA__IAEA_Presentation_June_2014.pdf

I am very bad in corrosion but It seems in this paper that CVD SiC is highly resistant to corrosion in clean Flibe or I don't understand the paper. Even the other types of SiC seem good. Maybe chemical vapor deposition is too costly or difficult.


CVD and CVI serve different markets. CVD is good when you want a thin, high quality layer. As in semiconductors, or in the nuclear cladding application, as a hermetic barrier coating. CVI is more suitable for the "rough work". Bigger parts, where a high residual porosity and such are not a problem, that is is a good application for CVI. You could probably use both, if it is economic. Presumably you'd have triplex construction, with an inner fiber structural part that could be CVI bonded, then sandwiched with CVD layers for hermetic containment. High temperature baking in carbon powder to further reduce free silicon on the surface, I think is a good idea to explore.

I don't think cost is that big a deal. High quality zircalloy cladding fabrication is around 0.1 cent/kWh or less. Cutting cost would be important for the actual companies providing the fuel, but its not a deal breaker for the business case of the nuclear plant on the whole.


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PostPosted: Dec 23, 2014 12:35 pm 
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Thanks for the explications Cyril.
There are concepts with zircaloy tubes wrapped by one or several layers of differents types of SiC materials ( CMC SiC, ...) for extra strength and corrosion resistance for LWRs. These concepts could also be interesting for Transatomic, no ? (if SiC can resist to corrosion in fuel salts)


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PostPosted: Dec 24, 2014 8:15 am 
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fab wrote:
Thanks for the explications Cyril.
There are concepts with zircaloy tubes wrapped by one or several layers of differents types of SiC materials ( CMC SiC, ...) for extra strength and corrosion resistance for LWRs. These concepts could also be interesting for Transatomic, no ? (if SiC can resist to corrosion in fuel salts)


Yes this has been produced already, to deal with the difficult problem of sealing SiC hermetically. Question is what happens to the zircalloy if some of the SiC breaks or flakes off and the Zr touches fuel salt. If it results in detrimental degradation then Zr tubes aren't safe. I suppose the Zr corrosion rate can be made very low if the salt is sufficiently reducing, and maybe local failure of the SiC layers won't deteriorate the Zr, but that's just a guess.

I would also expect Zr to have some reaction with hydride moderator, considering the temperature, or some of the free hydrogen that will exist in equilibrium in the moderator rods, and that this would not be a nice reaction, either.


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PostPosted: Dec 26, 2014 3:06 pm 
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Quote:
Wasn't there a presentation at TEAC two years ago that basicaly said it was INcompatible?


https://www.youtube.com/watch?v=Ykln5fyBM9E

Dr. Boyd presented on this subject at TEAC5.

To the best of my knowledge, a molten salt test loop is coming to Georgia Tech via a DOE program for the molten salt cooled reactor. AFAIK FLINAK and FLIBE will be tested, and SiC is supposed to be one of the materials tested.

If I understand correctly, it will be about 6 months to a year or so before the loop is actually testing, and until then it will be a lot of theoretical work. I should be able to work on it as an undergraduate, but if I can make it to grad school I'll be able to work on it as my thesis, I think.


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PostPosted: Dec 27, 2014 2:39 pm 
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fab wrote:
I am sorry, I saw several times papers with SiC used in MSRs concepts so I thought it was compatible. I will look more at this subject.


At least ORNL is working on this with their fluoride salt test loop:
http://inspire.ornl.gov/OriginalDocumen ... 5fbad07800


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