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PostPosted: Aug 16, 2010 2:51 pm 
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NNadir, if, hypothetically, it turned out that almost 100% purity Cl-37 could be enriched at reasonable cost/kWh, would you not oppose chloride reactors anymore? Trace Cl-36 would have a tendency to burn out to much lower equilibrium since it has higher absorbtion cross section than Cl-37. With these molten fuelled fast reactors you can also get serious flux levels that further help burning out Cl-36. Just be patient! The reactor will operate for decades. I think that chloride reactors may at least have some advantages in vacuum distillation over fluorides, and also in keeping more fast fission and slightly higher etas. Low fuel processing requirements are very attractive for cycles with lots of TRU since you make less of a mess and have less risk of making unintended messes. I know you like plutonium but it is nasty stuff in the environment. Gets on your bones and radiolyses you from within. Keep it in the reactor as much as possible.


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PostPosted: Aug 16, 2010 5:44 pm 
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Cyril R wrote:
I know you like plutonium but it is nasty stuff in the environment. Gets on your bones and radiolyses you from within.
Pu really? Dont you mean Sr?


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PostPosted: Aug 16, 2010 6:09 pm 
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Ondrej,
From the ANL Fact Sheet:
Quote:
What Happens to It in the Body?
When plutonium is inhaled, a significant fraction can move from the lungs through the blood to other organs, depending on the solubility of the compound. Little plutonium (about 0.05%) is absorbed from the gastrointestinal tract after ingestion, and little is absorbed through the skin following dermal contact. After leaving the intestine or lung, about 10% clears the body. The rest of what enters the bloodstream deposits about equally in the liver and skeleton where it remains for long periods of time, with biological retention half-lives of about 20 and 50 years, respectively, per simplified models that do not reflect intermediate redistribution. The amount deposited in the liver and skeleton depends on the age of the individual, with fractional uptake in the liver increasing with age. Plutonium in the skeleton deposits on the cortical and trabecular surfaces of bones and slowly redistributes throughout the volume of mineral bone with time.


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PostPosted: Aug 16, 2010 6:26 pm 
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jaro wrote:
For an inelastic collision of a 2MeV neutron with a U238 nucleus, the neutron energy drops to 0.6MeV on average -- using the formula E' = 6.4* sqrt(E/A), where A is the mass number.
For F19, the result of an inelastic neutron collision is about the same as an elastic one, for energies below about 2.5MeV ! (for the more extreme case of a 6MeV neutron, it drops to about 3.6MeV)
Thanks for looking all this up, but there's something funny about that E' = 6.4* sqrt(E/A) formula

E = 2, A = 238 --> E' = 6.4*1.41/15 = 0.6 OK
E = 6 A = 19 --> E' = 6.4*2.45/4.36 = 3.59 OK
E = 2, A = 19 -->E' = 6.4*1.41/4.36 = 2.07 ?
E = 1, A = 19 -->E' = 6.4*1/4.36 = 1.47 Huh?
E = 0.5, A = 19 -->E' = 6.4*0.71/4.36 = 1.04 Hey, who needs fission anyway!

The formula is obviously only an approximation, and it has to fail at low E and low A, so I don't think we can be sure about 19F and 2 MeV neutrons yet.


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PostPosted: Aug 16, 2010 6:51 pm 
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Luke wrote:
jaro wrote:
For an inelastic collision of a 2MeV neutron with a U238 nucleus, the neutron energy drops to 0.6MeV on average -- using the formula E' = 6.4* sqrt(E/A), where A is the mass number.
For F19, the result of an inelastic neutron collision is about the same as an elastic one, for energies below about 2.5MeV ! (for the more extreme case of a 6MeV neutron, it drops to about 3.6MeV)
Thanks for looking all this up, but there's something funny about that E' = 6.4* sqrt(E/A) formula

E = 2, A = 238 --> E' = 6.4*1.41/15 = 0.6 OK
E = 6 A = 19 --> E' = 6.4*2.45/4.36 = 3.59 OK
E = 2, A = 19 -->E' = 6.4*1.41/4.36 = 2.07 ?
E = 1, A = 19 -->E' = 6.4*1/4.36 = 1.47 Huh?
E = 0.5, A = 19 -->E' = 6.4*0.71/4.36 = 1.04 Hey, who needs fission anyway!

The formula is obviously only an approximation, and it has to fail at low E and low A, so I don't think we can be sure about 19F and 2 MeV neutrons yet.

You're absolutely right ! ....still looking for a better approximation ! 8)


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PostPosted: Aug 17, 2010 12:33 am 
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ondrejch wrote:
Cyril R wrote:
I know you like plutonium but it is nasty stuff in the environment. Gets on your bones and radiolyses you from within.
Pu really? Dont you mean Sr?


Pu forms unsoluble compounds (phosphates IIRC) which concentrate on the bone interface. Resulting in radiolysis poisoning (hydroxyl from water in cells). Sr also does something to your bones but I forgot what it was, something about selectively replacing calcium as structural material. Is this the same process?


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PostPosted: Aug 17, 2010 4:20 am 
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Cyril R wrote:
Pu forms insoluble compounds (phosphates IIRC) which concentrate on the bone interface. Resulting in radiolysis poisoning (hydroxyl from water in cells). Sr also does something to your bones but I forgot what it was, something about selectively replacing calcium as structural material. Is this the same process?
Not quite, I think. Sr is the element immediately below Ca in the periodic table. Its chemical properties are therefore rather similar to Ca, sufficiently so that biological processes that use Ca will attempt to use Sr if it is there. If you ingest Sr-90, it gets incorporated into the bones - particularly any areas that are growing - where it will likely remain until it decays. This helps to make Sr-90 much more hazardous than Cs-137, which is soluble and is soon excreted.


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PostPosted: Aug 17, 2010 5:30 am 
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Strontium Fact Sheet.....


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PostPosted: Aug 17, 2010 6:08 am 
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Luke wrote:
Cyril R wrote:
Pu forms insoluble compounds (phosphates IIRC) which concentrate on the bone interface. Resulting in radiolysis poisoning (hydroxyl from water in cells). Sr also does something to your bones but I forgot what it was, something about selectively replacing calcium as structural material. Is this the same process?
Not quite, I think. Sr is the element immediately below Ca in the periodic table. Its chemical properties are therefore rather similar to Ca, sufficiently so that biological processes that use Ca will attempt to use Sr if it is there. If you ingest Sr-90, it gets incorporated into the bones - particularly any areas that are growing - where it will likely remain until it decays. This helps to make Sr-90 much more hazardous than Cs-137, which is soluble and is soon excreted.


From what I’ve read, Pu doesn’t bind to collagen but nevertheless does accumulate on the bone surface via protein binding. This apparently makes it more dangerous than Sr and famous cousin Ra, since the concentration on the bone surface is very high and lots of hydroxyl is formed in neighboring tissues.


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PostPosted: Aug 17, 2010 5:47 pm 
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Human health effects of Plutonium exposure -- 50-year update on Manhattan Project workers.....


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PostPosted: Aug 17, 2010 6:07 pm 
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Thanks Jaro - nice to have some data to refer to if the topic of plutonium poisoning comes up. We've gotten pretty far off topic. Next post should be put in a more appropriate thread.


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PostPosted: Aug 18, 2010 11:42 am 
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Allright, let's talk chlorides!

I was thinking one way to go would be to startup on TRU (as trichlorides) and balance with thorium (as tetrachloride) with NaCl or KCl (or both) for eutectic melting point depression. It appears such eutectics have nadirs on the low end of 300 degrees C, which is great because we get compatibility with cheaper easy to work with materials, as well as current steam cycles. (perhaps as low as 400 C primary cold leg temp). As the reactor goes through the 'once through cycle', fission product buildup would take over some of thorium's role in absorptions (ie we balance with fewer fertile shim) and the reactor starts to run on U233 mostly. This rids us of most of the TRU at the end of the once through operation so it will be easier to reprocess. Chlorination may not be optimal for fuel removal, but U233Cl4 is easily removed by vacuum distillation, as is ThCl4, all at much lower temperatures than for fluorides (eg LiF, ThF4), so that's fine.


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PostPosted: Aug 18, 2010 4:16 pm 
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What's with the 5300 downloads ??? .....some sort of bug ?


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PostPosted: Aug 18, 2010 10:10 pm 
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perhaps some data mining software going on.


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PostPosted: Aug 19, 2010 12:09 am 
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jaro wrote:
For an inelastic collision of a 2MeV neutron with a U238 nucleus, the neutron energy drops to 0.6MeV on average -- using the formula E' = 6.4* sqrt(E/A), where A is the mass number.
For F19, the result of an inelastic neutron collision is about the same as an elastic one, for energies below about 2.5MeV ! (for the more extreme case of a 6MeV neutron, it drops to about 3.6MeV)


Hmm. E'=6.4*sqrt(E/A)>=E (seems impossible) when E <= 6.4^2/A. For F-19, that's E <= 2.156. For U-238, that's E <= 172 KeV.

But Fluorine has a significant inelastic cross-section below 2.156 MeV. Am I misunderstanding the equation, or does it not apply to Fluorine?

-Iain


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