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 Post subject: ~ 20% uranium enrichment
PostPosted: Dec 10, 2010 4:01 pm 
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Considering that a DMSR needs thorium + LEU enriched at a level slightly lower than 20%, we need it. Is it a problem (I don't know, say, for politics, proliferation, capacity reasons) to produce that using current infrastructures, both in North America, Japan or western Europe ?


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PostPosted: Dec 10, 2010 4:26 pm 
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Probably not for technical reasons, though many enrichment companies seem hesitant to get even close to 5% enrichment. But LEU is LEU and if the market for 19% enrichment get some momentum things might loosen up a bit. No thorium MSRs can use <5% enrichment that LWR use so if a major restraint then uranium only is a good way to get started. Also easier re-enrichment without having to get hasty in your centrifuge train, worrying about the U232 decaying to annoying gamma emitters. If enrichment companies give you hassle with 19% LEU then they may also give hassle with U232.

If you put in some transuranics from spent fuel, this puts in fissile so then either the total uranium or uranium enrichment level can be lowered. Good PR on the conceived waste issue as well. NaF based carrier salts have better solubilities for the trifluorides. LiF NaF BeF2 has decent neutronic performance and much reduced melting point compared to FLiBe.


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PostPosted: Dec 10, 2010 6:30 pm 
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Cyril R wrote:
...if the market for 19% enrichment get some momentum things might loosen up a bit.

That's exactly right.

The flip side though, is that currently there exists no large (civilian) customer base for fuel >5% enrichment, so its only available through very special arrangements, and pretty much unique sources (i.e. fuel for existing & proven research reactors and Mo99 radioisotope production targets -- typically derived from down-blending ex-weapons HEU).

Even fuel with <5% enrichment is only available to recognised clientelle, such as utilities and large reactor design & development groups that are typically part of multinational corporations.

I don't think anyone here believes that these are the kind of outfits that will develop MSRs.
Even upstarts with very deep pockets (Hyperion, TWR) are avoiding MSRs.

Realistically then, any other group wishing to develop MSRs would make life a lot easier for itself by abstaining from fuel that uses >5% LEU -- and better yet, just starts the development program with plain old NU.


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PostPosted: Dec 11, 2010 3:26 am 
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What you say is true, but its probably unavoidable to go with big companies and big government anyways. The reactor design itself is so deviant from solid fuel reactors, IMHO the development and engineering requirements completely dwarf any discussion on what level of enrichment to use for startup. Just look how many prototypes and engineering it took to get momentum (commercialization) on CANDUs. And that's really not as deviant as an MSR. Its still solid fuel and UO2. Pretty conservative I would say. This should be a warning to anyone trying to develop an MSR with a 'one prototype to victory' strategy. I fear it will not be that easy.

A uranium DMSR could probably start up on natural uranium + TRU. Personally I think it will be easier to start it up almost completely on mined U and just go for the 4-5% enrichment. However eating waste is a good way to get government and possibly also private funding. It is also advantageous to put in some TRU at start from a proliferation angle, since no Pu239 could be cleanly extracted at beginning of reactor life. With no thorium there is also no fissile U233 bred so there is no denaturing requirement here and thus you could even consider feeding it mostly TRU for the top-up fuel as well. The NaF based carrier salts seem to be able to take the trifluoride loading. With no online fuel processing, actinide leakage can be very low. Fluorination and re-enrichment (if using LEU) is very simple and a one time TRU recovery might also be attractive with the newer processing methods.


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PostPosted: Dec 11, 2010 6:57 am 
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Russian SVBR designs work with less than 20% enrichment. The Russians are a major suppliers of experimental/Power reactor fuel and could take on the supply of uranium fuel anywhere. Indian LEU version of AHWR design carries 78% thorium with 22% of 19.75%LEU. Only Russian origin uranium can be expected if and when it is actually built. MSR's are more neutron efficient than the solid fueled reactors due to escape/removal of Xe fission product and could use some thorium too.
I think that uranium enrichment should be standardized to 20% and thorium should be used to extend the power production from uranium. DU can be burnt in fast reactors with recovered plutonium. This will reduce uranium requirements till thorium fueled reactors come into general use.


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PostPosted: Dec 15, 2010 4:29 pm 
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The OPAL reactor at Lucas Heights in Sydney uses U enriched to just below 20%. The fuel plates are sourced from Argentina.


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PostPosted: Dec 16, 2010 9:42 pm 
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And HIFAR before it used HEU, IIRC.

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