Energy From Thorium Discussion Forum

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PostPosted: Aug 25, 2010 7:46 am 
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jagdish wrote:
Chloride reactors are basically for hard spectrum. Metallic fuel is even better for this purpose. Why not extend it to fluid fuel?
A Pb-Pu eutectic could be used as fluid fuel. Other TRU's can join Pu or be filtered out. Fertile feed, Uranium or thorium, need not be fully dissolved and could be placed as rolls of metallic U or Th perforated sheet or wire gauze. If there is thorium, it could be electro-refined to recover U-233 with protective U-232
Could a reactor get critical with Pb-Pu in voids of Uranium-238 pebbles?. Fertile/Fissile ratio could be low and smaller quantity of fertile with higher space for fissile as described may be necessary.

Why do you think Pb-Pu eutectic is better than a chloride salt? Metallic fuel certainly isn't superior to chloride reactors in terms of neutron budget or neutron spectrum.


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PostPosted: Aug 25, 2010 10:08 am 
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A metallic fuel will require less volume for same energy output and therefore be economical. Chlorine brings in uncertainly about Cl36 and fluorides about corrosion. It is, of course only loud thinking on my part and there might be complications that are not yet known.


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PostPosted: Aug 25, 2010 10:49 am 
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Metallic fuel may get you a little bit better neutron budget, but not with all that lead in there. If you're worried about a small radioactivity inventory of chlorine-36, then maybe you have to think what happens to your metallic fuel when it finds water or air. It isn't pretty. I think metallic fuelled reactors are cool, but realistically, who wants to bet that you can even license the darn things? There was a plan to transmute actinide waste in a fusion reactor but it was shot down because they used... metallic liquid actinides!!!

Chlorine-36 is not a major radioactivity hazard in the reactor simply because of the gigacuries of other stuff in there. Cl-36 has a higher capture cross section than Cl-37 and will eventually burn out, mostly to Cl-37 which is what we want. All we have to do is add pure Cl-37 makeup and Cl-36 will eventually vanish. Such an option exists: calcium. Ca-40 (n,a) -> Ar-37 (decays) -> Cl-37. Calcium can be added as calcium chloride, which is a good carrier salt addition, or as pure substance, perhaps in a seperate circuit in the core.

Corrosion can be engineered out by proper materials and coatings (pyc, nickel, noble metals etc) and by not allowing a large quantity of Cl-35 in the reactor.


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PostPosted: Aug 25, 2010 4:04 pm 
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jagdish wrote:
A metallic fuel will require less volume for same energy output and therefore be economical. Chlorine brings in uncertainly about Cl36 and fluorides about corrosion. It is, of course only loud thinking on my part and there might be complications that are not yet known.

Why do you think it requires less volume? You need just as much coolant for the reactor core. Its more compact than a LWR, sure, but not a chloride reactor. Economical and liquid metal cooled just don't belong in the same sentence. Pb-Bi eutectics have a polonium production and corrosion issues of their own, as well as fuel fabrication regimes. Once you get into trying to do fuel fabrication with hot fuel, your cost model goes out the window. You don't get anything from liquid metal cooled reactors except a giant headache. I mean, we've been tinkering with them for the past fifty years or so and they're still little more than expensive toys despite having the lions share of funding.

With chloride reactors you can get harder spectrum, better neutron budget, and better reactor efficiency as a two fluid system wont waste any neutrons. Cl-36 concerns are bizarre at best, given its low activity and short bioactive half-life. About the only thing that I can see bad about it is its very biomobile, so it can go everywhere. But it doesn't stay anywhere. The chemistry is convenient for online fuel processing.


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