Energy From Thorium Discussion Forum

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PostPosted: Oct 21, 2013 1:02 am 
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NicholasJanssen wrote:
academia and their helium pipedreams!

http://www.periodictable.com/Properties ... ius.v.html
helium has the smallest atomic radius


The leakage of helium will not be a problem, because there are many industry use of helium such as low temperature engineering. besides the comerical use, the helium cooled high temperature reactor also choose helium as colant.


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PostPosted: Oct 21, 2013 1:15 am 
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Helium leakage is not as bad as it might first imply since it tends to be a slow diffusive leak.

Which means the only thing it does it mean you have to buy more helium.
Its an operational cost, since it doesn't react with anything or even get neutron activated that it is all it is.


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PostPosted: Oct 21, 2013 5:00 am 
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It does imply higher cost for seals and such, to affect tight seals very tight tolerances must be held. Yes you can buy more helium, but if there's tritium in the helium, then it's another story entirely. Leaking tritium contaminated helium everywhere is not going to be acceptable. Extremely rapid and efficient tritium removal from the helium loop would be necessary, and even then you still get some equilibrium tritium around. Elemental tritium leaks and diffuses even easier than helium.

Low temperature helium cryogenics isn't a good comparison. There's no tritium there, and low temperature and low pressure means little leakage and diffusion to begin with.

Also helium as secondary loop means no natural circulation heat removal for decay afterheat. That means considerably less defense in depth. You must quickly dump the salt in the event of a disturbance or power failure, and any entrained fission products that are left behind on the HX will heat it up to failure. Supercritical CO2 may be more attractive in this regard.


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PostPosted: Oct 21, 2013 10:15 am 
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longwei1221 wrote:
The leakage of helium will not be a problem, because there are many industry use of helium such as low temperature engineering. besides the comerical use, the helium cooled high temperature reactor also choose helium as colant.

E Ireland wrote:
Helium leakage is not as bad as it might first imply since it tends to be a slow diffusive leak.

Which means the only thing it does it mean you have to buy more helium.
Its an operational cost, since it doesn't react with anything or even get neutron activated that it is all it is.


Helium never works in real life.


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PostPosted: Oct 21, 2013 1:12 pm 
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Actually quite a few succesful helium cooled reactors were built. The Fort St. Vrain reactor for example worked very well, the biggest technical problem was actually steam leaking not helium leaking. But it was an economic failure. Helium has very poor economics, with all the downsides of high pressure operation but none of the advantages of the superiour coolant that water and molten salts have. The only really succesful gas cooled reactors are CO2 cooled reactors in Great Britain.


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PostPosted: Oct 21, 2013 2:58 pm 
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And Italy and Japan.... and North Korea.

(The reactor at Yongbyong was built using declassified drawings from the Magnox plants at Calder Hall in Cumbria.... really need to get a copy of those plans to stick up on the wall)


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PostPosted: Oct 22, 2013 6:50 am 
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Cyril R wrote:
Actually quite a few succesful helium cooled reactors were built. The Fort St. Vrain reactor for example worked very well, the biggest technical problem was actually steam leaking not helium leaking. But it was an economic failure. Helium has very poor economics, with all the downsides of high pressure operation but none of the advantages of the superiour coolant that water and molten salts have. The only really succesful gas cooled reactors are CO2 cooled reactors in Great Britain.


Attached is HTR-10 helium cooled reactor
http://en.wikipedia.org/wiki/HTR-10
it reached critical in December 2000 and was operated in full power condition and produced electricity in January 2003
maybe there are still many problems for helium as coolant, but it can be.
as for molten salt reactor, why shouldn't we borrow the helium coolant technology?


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PostPosted: Oct 22, 2013 7:36 am 
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longwei1221 wrote:
as for molten salt reactor, why shouldn't we borrow the helium coolant technology?


Because molten salts are far superiour coolants in almost every respect to helium?


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PostPosted: Oct 22, 2013 8:21 am 
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longwei1221 wrote:
Cyril R wrote:
Actually quite a few succesful helium cooled reactors were built. The Fort St. Vrain reactor for example worked very well, the biggest technical problem was actually steam leaking not helium leaking. But it was an economic failure. Helium has very poor economics, with all the downsides of high pressure operation but none of the advantages of the superiour coolant that water and molten salts have. The only really succesful gas cooled reactors are CO2 cooled reactors in Great Britain.


Attached is HTR-10 helium cooled reactor
http://en.wikipedia.org/wiki/HTR-10
it reached critical in December 2000 and was operated in full power condition and produced electricity in January 2003
maybe there are still many problems for helium as coolant, but it can be.
as for molten salt reactor, why shouldn't we borrow the helium coolant technology?


I don't think HTR-10 will work correctly. HTR-10 is bad design.


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PostPosted: Oct 22, 2013 9:32 am 
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HTR-10 appears to be working fine. For years in fact.


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PostPosted: Oct 22, 2013 7:44 pm 
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NicholasJanssen wrote:

I don't think HTR-10 will work correctly. HTR-10 is bad design.


HTR-10 is not as bad as you think, it works well. their next step is helium Brayton cycle for electricity generating, they are working for it now.


Cyril R wrote:
Because molten salts are far superiour coolants in almost every respect to helium?.

Yes, just as coolant, molten salt is better than helium, but here we discuss helium is for electricity generating, you couldn't use molten salt do cycle and generate electricity power right? steam rankine cycle or helium brayton cycle? I think the latter is better for MSR.


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PostPosted: Oct 22, 2013 8:47 pm 
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I agree about Brayton, but remember that because an MSR would run a Brayton cycle indirectly, you can use working fluids other than helium. Nitrogen, argon, and CO2 are all viable options as well.


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PostPosted: Oct 22, 2013 10:46 pm 
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Kirk Sorensen wrote:
I agree about Brayton, but remember that because an MSR would run a Brayton cycle indirectly, you can use working fluids other than helium. Nitrogen, argon, and CO2 are all viable options as well.

Kirk, Thanks for your MSRE diagrams! How are you?

Suppose that we choose brayton cycle, which kind of fluids is better? from thermal conductivity viewpoint, hydrogen is the best, helium take the second place, considering the stability, helium is better for cycle, isn't it?


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PostPosted: Oct 22, 2013 10:53 pm 
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longwei1221 wrote:
Suppose that we choose brayton cycle, which kind of fluids is better? from thermal conductivity viewpoint, hydrogen is the best, helium take the second place, considering the stability, helium is better for cycle, isn't it?
I kind of like the idea of the SuperCritical CO2 brayton.

_________________
DRJ : Engineer - NAVSEA : (Retired)


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PostPosted: Oct 23, 2013 4:24 am 
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Proposals for revival of nuclear power in the UK are being criticized for high cost. US reactors are also finding it difficult to continue in face of cheap (temporarily) shale gas. If Nitrogen, Argon or CO2 can act as coolant in MSR, costly gases like Helium should not be used.
Similarly isotopically ultra-pure 7Li as part of FLiBe will render the MSR economically unfeasible. NaF-BeF2 or NaF-ZrF4 will be a better bet. Operating temperatures will not be effected. Neutron absorption and moderating action will be to some extent. Thorium should best be kept as metal both in internal fertile as well as the reflector/blanket. It could be easily reprocessed by electrolysis.


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