Energy From Thorium Discussion Forum

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PostPosted: Feb 15, 2014 3:32 pm 
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Is there now a consensus on which is better, one fluid combined core and blanket, or two fluid one for the core and one for the blanket? Or other?

I guess this should be in reactor design rather than general discussion. If you have the authority to move this please feel free to. Thanks.


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PostPosted: Feb 16, 2014 4:30 pm 
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A consensus? In the world of molten salt reactor proponents?

That's funny. This should go in the humor section of the forum.


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PostPosted: Feb 18, 2014 11:43 am 
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There is not even agreement about which salts to use. And not much agreement about the spectrum (thermal, fast, in-between, etc.). And not even if it is to be a burner, breeder or iso-breeder.

As far as 1 fluid versus 2 fluid: the simple version is - do you want to tackle the salt processing challenges of 1 fluid reactors, or the plumbing issues of 2 fluid reactors (FYI, I'm picturing an iso-breeder using a graphite moderator and FLiBe salt).


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PostPosted: Feb 18, 2014 2:28 pm 
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2 fluid rules dude!

on a serious note, I consider the plumbing issues more easily to tackle given the advancements in material science.

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PostPosted: Feb 18, 2014 4:05 pm 
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Jim L. wrote:
I'm picturing an iso-breeder ...
Sustainer?

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PostPosted: Feb 18, 2014 8:04 pm 
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At the time when even LWR's are being eased out by temporarily cheap gas, simpler and lower capital cost, is the better option. One fluid may get the MSR going for later refinements.


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PostPosted: Feb 18, 2014 9:27 pm 
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Low risk is even more important than low cost. If the first new MSR's have problems, it will set the field back decades.

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PostPosted: Feb 19, 2014 12:05 am 
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Thank you everyone. I did not expect this to be such an interesting topic.


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PostPosted: Feb 19, 2014 6:07 am 
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pstudier wrote:
Low risk is even more important than low cost. If the first new MSR's have problems, it will set the field back decades.



this is why the first commercial MSRs must be 2 fluid.
In the 1 fluid approach the complicated chemistry makes for a large time spent by the fuel salt outside the reactor, hence increased probability of accident, human exposure, fuel theft etc. which translates into a PR nightmare.

In the 2 fluid design even if the plumbing fails the consequences are less dramatic, the fuel salt mixes with the fertile salt, the reaction dies of, no environmental exposure, everything stays inside the reactor.

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PostPosted: Feb 19, 2014 7:52 am 
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If the plumbing fails you essentially lose the reactor.

You will never get permission for a restart even if you can work out a way to repair it.


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PostPosted: Feb 19, 2014 11:32 am 
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My first urge is to say... "ridiculous". I'll merely say "I disagree" instead.

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PostPosted: Feb 19, 2014 11:36 am 
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You will end up with a full load of salt which has been converted into what amounts to one fluid reactor salt - which will have to be shipped out, then you will have to find some way of decontaminating the reactor sufficiently to allow repairs to be made, then you will either have to construct a plant from scratch to recover the fissile material from the original salt load or you will have to procure a new fissile load.

Once the costs are in its not much cheaper than simply calling it quits and buying another reactor.


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PostPosted: Feb 19, 2014 12:37 pm 
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@KitemanSA - sure, call it 'sustainer' if you like, I think I've seen the term 'iso-breeder' most often. I'm referring to a design where the conversion ratio - 1.00.


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PostPosted: Feb 19, 2014 8:34 pm 
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Even in a sustainer system, there will be some retirements and replacements. Conversion ratio is required to be more than one. It is like a fertility of 2.1 rather than 2.0 is required for maintaining a constant population.
As things stand, the production of mined uranium, the source of fissile fuel, is now mainly in Central Asia and Africa. It has already plateaued in Canada and Australia, partly due to local resistance. It is now desirable to build up fissile as it is consumed. It is also important to bury only the fission products and re-use the Actinides.


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PostPosted: Feb 19, 2014 9:05 pm 
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Remember that the absolute ceiling of uranium prices has fallen to roughly $660/kgU and is still falling.
Seawater extraction can take up the slack left by mining.


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