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PostPosted: Feb 25, 2010 1:52 pm 
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Idaho Samizdat: Pebble-bed reactor loses funding

Looks like the original article in the thread was right.

I think that when they made the choice to go with a conventional Rankine cycle vs. a Brayton they lost a key unique feature. Why buy a pebble-bed Rankine when you can buy an LWR Rankine?

But they had problems because they were using the direct Brayton cycle and they couldn't keep contamination out of the turbomachinery. Using indirect Brayton in LFTR should help to reduce this problem considerably.


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PostPosted: Feb 26, 2010 4:23 pm 
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Joined: Mar 07, 2007 11:02 am
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Kirk Sorensen wrote:
Idaho Samizdat: Pebble-bed reactor loses funding

Looks like the original article in the thread was right.

I think that when they made the choice to go with a conventional Rankine cycle vs. a Brayton they lost a key unique feature. Why buy a pebble-bed Rankine when you can buy an LWR Rankine?

But they had problems because they were using the direct Brayton cycle and they couldn't keep contamination out of the turbomachinery. Using indirect Brayton in LFTR should help to reduce this problem considerably.


I am a little confused Kirk, were they actually looking at a steam Rankine at some point for the PBMR, I thought it was always helium Brayton, but that they chose a simpler, cheaper and less efficient variant than multi-reheat Brayton.

I agree that an indirect Brayton helps with the turbomachinery but I would also say that the South African experience is a bit of a cautionary tale for anyone looking to develop a Brayton cycle to match a reactor (heilum or supercritical CO2). I`m not saying there isn`t a big long term advantage but it seems the expensive of trying to get the PBMR Brayton cycle developed was a pretty big factor in their failure overall. Using a super or ultra super critical steam cycle and matching to a LFTR might be a more direct route. ORNL had to change the cycle a little, by preheating feedwater with steam injection because of the high melting point of the intermediate cooling salt but that challenge is minor compared to the billion(s?) need to develop a new gas turbine. Regardless, it is great we have the luxury of choice.

David L.


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