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 Post subject: Re: Lifespan of a LFTR?
PostPosted: Feb 25, 2011 8:58 pm 
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Joined: Nov 30, 2006 9:18 pm
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Location: Montreal
David wrote:
One day I asked him, what if the peak temperature was down to 550 or so? Oh sure, then anything will work was his response!

Well, not really.
Even in good old CANDU reactors a mistake was made in making some small components out of stainless steel -- needless to say, the helium production from neutron absorbtion by nickel turns the metal to mush.
Bad idea.


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 Post subject: Re: Lifespan of a LFTR?
PostPosted: Feb 26, 2011 2:46 am 
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Lindsay, just to let you know my position, I absolutely agree that 1600 C MSRs are silly to even suggest. In fact I'd prefer Dr. LeBlanc's approach of a lower temperature salt, such as FLiNaBe (equal parts). We only need to get steam >500 C which means a secondary loop of 550 C and maybe 600 C in the primary fuel loop. Cheaper and/or longer lasting materials. In fact I've started a thread on this topic:

viewtopic.php?f=3&t=2432&start=0&st=0&sk=t&sd=a

But to be pedantic and crazy like a spiked cornflake eating individual, I'd have to say that LiF boils at 1676 C. The fission products would be nasty at these temperatures, though I've wondered if Per Peterson's AHTR could in the distant future be run on pure 7LiF. Perhaps even a boiling LiF reactor, how's that for crazy ideas.

However, there is another problem: I don't like cornflakes. :mrgreen:


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 Post subject: Re: Lifespan of a LFTR?
PostPosted: Feb 26, 2011 4:36 am 
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Thanks Cyril.

Here's one that blew my mind by Taube et al 1967 A boiling salt fast breeder concept cooled by boiling AlCl. I presume that Taube ate regulation corn flakes, but that concept almost did my head in.


Last edited by Lindsay on Feb 26, 2011 9:27 am, edited 1 time in total.

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 Post subject: Re: Lifespan of a LFTR?
PostPosted: Feb 26, 2011 5:16 am 
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Actually that design is quite safe, as the thermal expansion of the fuel shuts down the reactor upon overheating. The pressure is a bit high though, over 30 atmospheres. The idea of a mercury or AlCl3 power cycle is much less appealing as well. And, perhaps I'm just being ornery again, but I really don't like direct contact cooling systems with lead or helium.

Boiling water reactors however work fine. While it may appear at first glance that removing barriers reduces safety, the reverse is actually true since the simplicity of the one loop system allows passive safety to be built in easily, always keeping the core covered under water. But with boiling salt and fission products in the fuel/coolant á la MSR the advantages are smaller and the challenges huge.

For a LFTR I would much prefer a fluoride coolant and heat exchanger to intermediate loop followed by another loop with huge amount of solar salt (eutectic NaNO3 KNO3, equal parts). No phase change, use the wide experience from MSRE and the ARE as starting point. The addition of solar salt allows better integration with the steam turbine, tritium trapping, and a large low cost simple yet effective heat buffer for thermal storage, decay heat removal and other thermal management. And, its off the shelf technology.


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