Energy From Thorium Discussion Forum

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PostPosted: Oct 01, 2010 3:54 pm 
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Some have mentioned how hard it might be to obtain supplies of uranium enriched to higher than 5%, for example I think it was mentioned that the PBMR folks had a hard time when looking for 8% enrichment. Can someone offer a little more insight regarding enrichment plants licensing and how hard it would be to go higher? Enrichment levels have been slowly rising for a couple decades so it certainly isn't out of the question to imagine higher levels (4.5 to 5% is getting common). There is a lot of talk of introducing annular fuel elements that would need 6.5% to 7.5%.

I know going all the way to 20% enrichment is a big stretch for current facilities but how hard do people feel it would be to get supplies of 6%? 8%? 10%? 15%?

This would be in connection with a DMSR design which was designed to run on 20% with as much thorium as possible but it can certainly be modified with lower enrichments, all the way down to about 5% LEU without any thorium. I am hoping at least 7 or 8% for makeup is at least something that won't be that hard.

David LeBlanc


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PostPosted: Oct 01, 2010 4:27 pm 
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You should hurry up and get some from the Megatons to Megawatts project. See http://en.wikipedia.org/wiki/Megatons_to_Megawatts_Program . It ends in 2013 and has down-blended 400 tons of Russian HEU.

It seems to me that the US department of defense probably also has more HEU than it needs.


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PostPosted: Oct 01, 2010 5:47 pm 
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A report from ORNL on world enrichment capabilities lists Areva's George Besse II plant as being licensed up to 6%, although their own web site says 2%-5% is available at the moment.


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PostPosted: Oct 01, 2010 6:50 pm 
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David,
It all depends on how deep your pockets are, and how closely you are tied to the government.
For instance, NRU driver fuel is 19.5% -- courtesy of the US DoE, thanks to decades of bilateral colaboration with Canada.
Any commercial newcomer can expect to be left out in the cold, as it were, with only commercial fuel suppliers as a viable source (and even there, you have to have a pretty solid backing to get anything, not to mention all sorts of licenses....).
So I think that a safe bet is that any new commercial venture proposing to build MSRs must assume *at best* 5% LEU.
The exception would be some kind of partnership with a US federal lab -- such as the Savannah River project with Hyperion. But it remains to be seen what, if any, success that will actually create in the end....
By far the easiest route would of course be NU.


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PostPosted: Oct 01, 2010 9:08 pm 
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At the FHR conference at ORNL two weeks ago a B&W representative mentioned that they have a license to enrich up to HEU, so I guess one could ask them for LEU above 5%.


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PostPosted: Oct 01, 2010 9:37 pm 
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ondrejch wrote:
At the FHR conference at ORNL two weeks ago a B&W representative mentioned that they have a license to enrich up to HEU, so I guess one could ask them for LEU above 5%.

B&W has an enrichment plant ? .....please do tell !


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PostPosted: Oct 01, 2010 10:07 pm 
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I think they are involved with McDermott plant, I dont know any details. The B&D talk by Scott Nagley is available here: https://www.ornl.gov/fhr/agenda.html

Perhaps you can ask Dr. Nagley by email, the contact info for the workshop participants is also posted the website: https://www.ornl.gov/fhr/

Kudos to the organizers for publishing all this information on-line.


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PostPosted: Oct 02, 2010 8:26 am 
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jaro wrote:
ondrejch wrote:
At the FHR conference at ORNL two weeks ago a B&W representative mentioned that they have a license to enrich up to HEU, so I guess one could ask them for LEU above 5%.

B&W has an enrichment plant ? .....please do tell !


B&W owns Nuclear Fuel Services (NFS) that performs the HEU blend down. It is this blend down that would potentially represent a source of material > 5 wt%. B&W also manufactures fuel for research reactors using HEU.


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PostPosted: Oct 02, 2010 11:55 am 
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Jess Gehin wrote:
B&W owns Nuclear Fuel Services (NFS) that performs the HEU blend down.

Thanks Jess,

I just read the B&W presentation from the ORNL workshop (....and recalled that this was mentioned some time ago on this forum).

https://www.ornl.gov/fhr/presentations/Nagley.pdf
Quote:
Babcock & Wilcox Nuclear Operations Group (NOG)
Facility Licensed for up to 100% U235 Enrichment
B&W is the only commercial US manufacturer licensed above 5%

NOG (Lynchburg, VA) Facilities
Medical Isotope Targets
4000 HEU Targets for AECL

Uranium Downblending
USEC Sapphire & 50 MT HEU Projects
Over 650 MT LEU Produced

Nuclear Fuel Services (Erwin, TN) Facilities
Uranium Downblending
TVA BLEU Project (~35 MT HEU)
Includes U Oxide Conversion for Areva
US DOE Reliable Fuel Projects
17 MT & 12 MT
Over 1000 MT LEU Produced


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PostPosted: Oct 03, 2010 5:20 am 
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I think down-blending of HEU should be done to 20%LEU only. All new enrichment facilities should also go to 20%. 20% LEU is the new recommended enrichment for experimental reactors and can be even used for fast spectrum reactors such as new Hyperion design or SVBR100. Calculations of Indian BARC for AHWR300LEU.broc show that blending this preferably standardized LEU with thorium gives an economical, long burn up fuel. This would be the best way to extend use of uranium and to introduce thorium in nuclear fuel in existing reactors.
This fuel could also be used to start a DMSR or LFTR.


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PostPosted: Oct 05, 2010 2:58 pm 
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David,
It is the licensing of the vendor facilities that restricts enrichments to 5%. At 5% in air you don't have to consider geometric effects, Keff<.98.
Above 5% you have to design the facility with constraints. As far as I know, only NFS can provide over 5% commercially and it's all downblended.


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PostPosted: Oct 06, 2010 9:07 am 
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I hope the French and Russians do not have such restrictions and can sell 20%LEU for Th-LEU reactor fuel.


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PostPosted: Oct 06, 2010 9:27 am 
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Jay Ely wrote:
David,
It is the licensing of the vendor facilities that restricts enrichments to 5%. At 5% in air you don't have to consider geometric effects, Keff<.98.
Above 5% you have to design the facility with constraints. As far as I know, only NFS can provide over 5% commercially and it's all downblended.



Jay,

Can you explain that a little further. Does this mean that UF6 at 5% or less as a gas can't reach criticality no matter the volume (i.e. a huge leak before it cools and solidifies), but that above 5% it can?

David L.


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PostPosted: Oct 06, 2010 2:10 pm 
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David,
Sorry I was imprecise- the issue is with U3O8 or UO2 either as a pellet or powder. I don't know about the UF6, it comes in to the facility in sealed vessels and one fabricator uses steam jackets to boil off the UF6 for processing, the other a heated vacuum system. Since their license is for 5%, no UF6 over 5% is allowed. Actually they're reluctant to supply over 4.95%, I know of one batch at 4.98% but that was a one off. My assumption is that the UF6 is less restrictive, but I'll have to ask.


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PostPosted: Oct 07, 2010 10:37 am 
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Jay Ely wrote:
David,
Sorry I was imprecise- the issue is with U3O8 or UO2 either as a pellet or powder. I don't know about the UF6, it comes in to the facility in sealed vessels and one fabricator uses steam jackets to boil off the UF6 for processing, the other a heated vacuum system. Since their license is for 5%, no UF6 over 5% is allowed. Actually they're reluctant to supply over 4.95%, I know of one batch at 4.98% but that was a one off. My assumption is that the UF6 is less restrictive, but I'll have to ask.


Thanks again Jay. So I guess that means a big pile of UO2 at greater than 5% can theoretically reach criticality. In practice I'm sure this is of much lower concern than UO2 mixing with water which I'd imagine even 3% would be something to avoid. It would indeed be interesting to find out what an equivalent enrichment would be for UF6 (presumably solid to be dense) or UF4. At least with UF6 any criticality event would be almost immediately cut off by it converting to gas and expanding. Hard to guess one way or the other if a pile of solid UF4 would be more or less reactive than UO2. Fluorine is certainly more absorbing than oxygen so my weak guess would be that UF6 or UF4 might have higher enrichments before such an issue is relevant. For use in any molten salt design we'd never go to UO2.

David L.


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