Discussions of conventional and alternative energy production technologies.
by Dezakin » Mon 18 Oct 2010, 02:26:23
$this->bbcode_second_pass_quote('EnergyUnlimited', '')$this->bbcode_second_pass_quote('Dezakin', 'T')hey form equilibrium concentration because they form at low concentration. They're at worst annoying.
http://energyfromthorium.com/2010/06/20 ... n-poisons/
It is big annoyance.
Salt distillation would not be needed, if you don't have to remove neutron poisons other than Xe135.
There are other neutron poisons that form with much smaller cross sections yet aren't in equilibrium. If we could get rid of Samarium for instance then we have more neutrons to play with, which in thermal and epithermal spectra are always precious.
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')You can via brute force remove everything but the uranium using fluoride volatility of UF6 to my knowledge. I humbly bow to those more experienced in molten salt chemistry, but wasn't aware of any real showstopping problems with molten salt reprocessing. Things we'd like to do better sure.
I don't understand your argument.
Molten fluoride Thorium reactor converts Th232 into U233 (and a bit of U232).
Thorium doesn't form volatile hexafluoride like Uranium (and with some pain Plutonium) does.
Essentially you would isolate fissile isotope (and you may end up with
excursion, if you try it in naive fashion).
However bulk of initial thorium input will still remain mixed with fission products (neutron poisons) and so you will have to dispose this thorium - antithesis of thorium breeder concept.
That's where some misunderstanding may be. In a two fluid breeder, there is no thorium in the core. You're probably thinking of one fluid designs (like the one prototyped at ORNL), which has much more complicated reprocessing. There's two separate fluids, the outer blanket which is thorium fluorides where the uranium is extracted by fluoride volatility, and the inner core which doesn't have any thorium in it.
The two fluid core and blanket design is my favorite for several reasons. First the reprocessing is much simpler of course. But the other is that in a two fluid design the outer vessel is insulated from most of the neutrons by the blanket, and so can be selected much more for its chemical compatibility with the salt rather than its resistance to neutron damage. I believe that you still have to be aware of different electrochemical potential between the core/blanket barrier and the outer vessel wall, but it does open up more options.
Another advantage is breeding doesn't explicitly require protactinium partitioning in a two fluid system, and so you can decide weather to do partitioning or pay for a larger salt volume.
The downside is the barrier between the core and blanket is in a hell of neutron radiation, and so there's some question on weather it will have to be replaced every so often.
Edit:
This is David Leblanc's exploration of the various molten salt reactor concepts, along with his modified geometry two fluid design for a full breakdown of the issues with liquid halide breeders. Its quite helpful, and I think you might enjoy it:
http://energyfromthorium.com/2007/08/23 ... t-breeder/$this->bbcode_second_pass_quote('', '')$this->bbcode_second_pass_quote('', 'I')'ll forward your concern to the LFTR community forum relating to vacuum distillation material, as there are several chemists and nuclear engineers there with far more experience than I. I read something about tungsten being an appropriate tubing material
Would be nice if you let me know, what they think about it.
We have still some considerable problems with fabrication of bulk tungsten items (you will need long sections and significant diameters of tubing).
I don't know how relevant these can be though.