Lithium-7

Lars
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Re: Lithium-7

Post by Lars » Jan 10, 2011 6:48 pm

According to http://www.em.doe.gov/pdfs/pubpdfs/link ... 03_114.pdf there are 41 million kg of depleted lithium (depleted in 6Li so enriched 7Li) in inventory left over from the cold war.

From http://minerals.usgs.gov/minerals/pubs/ ... 450494.pdf
The stockpile originally contained about 42,000 metric tons of material, from which about 75% of the lithium 6 isotope had been removed.

That would make the material 99% 7Li.

Luke
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Re: Lithium-7

Post by Luke » Jan 11, 2011 8:17 am

From Axil's isotope separation link, above, the operation of the COLEX lithium enrichment process was appallingly lax. No attempt was made to recover mercury lost into the aqueous phase, it was just dumped down the river as mercury nitrate. We could certainly do much better, but I suspect the Ceradyne (or whoever) engineer was right. No commercial operator would be interested. Everyone who lived near/downwind/downstream and had any medical complaint would try to blame the plant, and defending the lawsuits could be ruinous, even if the operator won them all.

A rational analysis would probably show that if the process were run carefully, total mercury lost to the environment would be far less than the mercury pollution from the coal plants the LFTRs replaced, but that's not how it will be looked at.

Cyril R
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Re: Lithium-7

Post by Cyril R » Jan 11, 2011 9:07 am

Perhaps you guys are too pessimistic about using mercury in OECD countries. First Solar is manufacturing gigawatts of cadmium telluride panels, involving tons of deadly cadmium. Cadmium is being regulated out, but First Solar gets exemptions from such HM regs because they made a convincing case that the cadmium is effectively protected in glass modules and they take full lifecycle responsibility for the modules.

The enrichment company here offers various centrifuge based enrichment services from their Stable Isotopes branch. I sent them an email and they said they can use their centrifuge trains to enrich virtually any stable isotope, as long as you have a volatile molecular species. Lithium is not on their list, chlorine is.

http://www.urenco.com/content/63/Stable-Isotopes.aspx

Per Peterson
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Re: Lithium-7

Post by Per Peterson » Jan 14, 2011 1:33 am

Currently, all of the enriched Li-7 used in U.S. pressurized water reactors is imported from China.

ORNL has identified 4 different non-mercury chemical processes that have the capability to enrich lithium. The key need is to study each at bench scale and select the optimal one for scale up to commercial production.

This is an area that deserves priority, since the continued operation of over half of U.S. nuclear capacity (the PWRs) relies on the availability of Li-7.

It would be wise to develop a domestic U.S. Li-7 enrichment capability. Our calculations indicate that the existing U.S. inventory of partially enriched Li-7 is sufficient to start up 150 to 400 GWe of AHTRs or LFTRs.

Lars
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Re: Lithium-7

Post by Lars » Jan 14, 2011 12:51 pm

" ... existing U.S. inventory of partially enriched Li-7 is sufficient to start up 150 to 400 GWe of AHTRs or LFTRs"

Is this the 99% 7Li left over from the cold war?

Still needs most of the enrichment work to be done, right? Getting the last bit of 6Li out is the hardest part. Now seems like a good time to press for this in Congress since there is sensitivity to dependency on China due to the rare earths.

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ondrejch
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Re: Lithium-7

Post by ondrejch » Jul 24, 2011 10:31 pm

ISOFLEX supplies Li7 hydroxide monohydrate:

http://www.isoflex.com/isotopes/lithium7.html
Lithium-7 as Hydroxide Monohydrate (7LiOH•H2O) is mainly used in the nuclear power industry as an alkalizing additive to the coolant of the primary circuit of PWR-reactors to adjust water-chemistry pH. It is also used as the main component in ion-exchange membranes in water treatment applications.
Apparently they also sell enriched Ni metal ;-)
http://www.isoflex.com/isotopes/p_chart.html

jagdish
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Re: Lithium-7

Post by jagdish » Aug 20, 2011 8:30 pm

Perhaps the FLiBe cooled AHTR development will blaze the way for FLiBe availability. Simultaneously what about a fast spectrum MSR as suggested as a Simplified Waste Digester? It could be developed out of waste disposal funds. A far better prospect than Yucca? Nuclear physics could be worked out for thorium as replacement feeds. A chloride volatility/electrolysis pyroprocessing preliminary development could also be a useful bulk reducer.

Cyril R
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Re: Lithium-7

Post by Cyril R » Oct 23, 2011 2:05 pm

There appears to be another method to get enriched Li7, using distillation and the relative volatility difference between Li6 and Li7.
in the distillation process, lithium is heated to a temperature of about 550 C in a vacuum, well below its boiling
point. Lithium atoms evaporate from the liquid surface. Those of the lighter isotope
have a greater mean free path and are collected preferentially on a cold surface
positioned a few cm above the liquid surface. The theoretical separation efficiency is
about 8%, so that a multi stage process is required to produce a high degree of
separation.
http://www.mcis.soton.ac.uk/Site_Files/ ... r_No_5.pdf

This looks to be about as effective as the mercury amalgam seperation process. Probably more energy intensive, but that's not a big deal (heavy water looks much worse in energy cost due to smaller mass differences and lower isotopic feed abundance of deuterium).

Burghard
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Re: Lithium-7

Post by Burghard » Oct 24, 2011 4:16 pm

In the distillation process, lithium is heated to a temperature of about 550 C in a vacuum, well below its boiling
point. Lithium atoms evaporate from the liquid surface. Those of the lighter isotope
have a greater mean free path and are collected preferentially on a cold surface
positioned a few cm above the liquid surface. The theoretical separation efficiency is
about 8%, so that a multi stage process is required to produce a high degree of
separation.
Can we really enrich 7Li this way? If 6Li is to be enriched, the condensed lithium from the cold surface is molten in the next stage an so on. But what do we do in practice when we want to enrich 7Li? I don't see the difference when molten lithium is moved from the melting pot of one stage to that of the next one.

Lars
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Re: Lithium-7

Post by Lars » Oct 24, 2011 10:24 pm

Reading the rest of that report it sounds like they can produce 6Li this way but that they had practical difficulties and in the end both the US and UK used the mercury amalgam process.

djw1
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Re: Lithium-7

Post by djw1 » Nov 19, 2011 3:56 pm

Ran across a couple of old papers that talk about Li-7 enrichment by electromigration.
Apparently, the difference is charge per mass means that Li-7 ions concentrate
at the anode in an electrolysis cell and Li-6 at the cathode.
One paper Benarie, J Inorg Nucl Chem 1961, talks about enrichments factors
over 2. Another Yamura et al, J Nuclear Science and technology, 7, 1970
reports 1.78.

Is this the way out?

djw1
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Re: Lithium-7

Post by djw1 » Nov 20, 2011 9:01 am

Correction. Lighter isotope ends up at the anode.
Theory is that the lighter isotope is more responsive to
collisions with the electrons flowing toward the anode
than the heavier.

jagdish
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Re: Lithium-7

Post by jagdish » Nov 21, 2011 4:29 am

Li6 is such a strong neutron poison that 99.995% Li7 is generally specified. Mass spectrometer looks like the only feasible option.
BeF2 is considered too viscous to be used alone.
Time and cost are so much against FLiBe that it is better to go for a fast spectrum option.
Cl-37 for fast spectrum chloride, by contrast, can be used 99% pure, easily prepared by centrifuging.
If you just follow the IFR drill for partitioning the SNF, you get the chloride fuel for FS-MSR without conversion or fabrication. You could, of course, convert it to Cl-37 for better neutron economy and conversion to thorium cycle.
Kirk himself has proposed FS-Molten Chloride Reactor as a step en route to LFTR and in his Future Of Energy blogs as a simplified waste digester. It needs to be a sufficiently large landing till you can get your Li7.

jagdish
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Re: Lithium-7

Post by jagdish » Nov 22, 2011 12:19 am

There was an answer in this thread:
viewtopic.php?f=64&t=363&st=0&sk=t&sd=a&start=52
Li7 'Tails' from Li6 enrichment would be much less than 99.995% pure. It may be better to start the mass spectrometer with it as the energy consumed would be proportional to the total mass analysed. I still think that FLiBe is possible but not prudent.
There are those who say that from a neutronic perspective that MCFR can tolerate natural Cl, but regarding Cl enrichment do you have any references for off the shelf Cl37 enrichment?
Cl37 enrichment will in any case improve neutron economy.
The molecular weight difference of the two isotopic uranium hexafluorides is less than 1%. For chlorine compounds it will be nearly 4(CHCl3) or 5%(HCl).

Cyril R
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Re: Lithium-7

Post by Cyril R » Nov 23, 2011 4:48 am

What I would like to find out is how much looser the enrichment requirement would be for a faster fluoride reactor, for example the more recent French Molten Salt Fast Reactor. Looking at the Li6 n,t reaction, that is really steep on spectrum. How much more Li6 can we tolerate for such a faster reactor?

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