Energy From Thorium Discussion Forum

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PostPosted: Feb 05, 2017 1:59 pm 
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Joined: Jan 29, 2014 4:05 am
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Location: Vitoria-ES-Brazil
E Ireland wrote:
With the low price of enrichment 250 tonnes of mined uranium becomes ~135 tonnes of 1.2% uranium.

A CANDU fissions roughly 2% of the nuclei in a 1.2% enriched uranium fuel element.
That means that roughly ~1.1% of the nuclei are fissioned.

Without any reprocessing and using reactors you can phone up the vendor of and order today.


But is that what actual CANDU owners are actually doing, or what can be done, but isn't being done to minimize waste production ?
CANDUs obviously can run on natural uranium which would greatly increase energy extraction but would turn all of those 250 tons into spent fuel...

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PostPosted: Feb 05, 2017 11:19 pm 
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macpacheco wrote:
But is that what actual CANDU owners are actually doing, or what can be done, but isn't being done to minimize waste production ?
CANDUs obviously can run on natural uranium which would greatly increase energy extraction but would turn all of those 250 tons into spent fuel...


As far as I know no CANDUs are currently operated with enriched fuel - Embalse may do so soon as it appears it will be switched to 0.85% in line with the uranium being fed to Atucha I.
However if you are willing to build a 480 tube reactor and operate without adjuster rods (either by accepting the 36 hour reactor recovery time or by fitting safety critical booster systems) you can obtain burnups of ~8,900MWd/t with natural Uranium fuel. (See the burnup figures for Bruce A)

That would turn the 250 tons of uranium into spent fuel but fission something around 0.9% of the nuclei in it without enrichment.
It is worth noting that with natural uranium fuel, enriched Zirconium-90 can make a big difference and push burnup in a Bruce A type reactor to somewhere in the vicinity of 12,000MWd/t, which puts us around 1.2%

But enriching actually reduces uranium requirements in a CANDU quite drastically.
Indeed if you have 0.1% tails fraction you can push enrichment values quite high without surrendering uranium efficiency - for example 1.7% enriched fuel gives burnups around ~32,000MWd/t, which is comparable at that low tails fraction. It effectively turns your spent fuel into early-PWR fuel in small elements.


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PostPosted: Feb 08, 2017 4:35 am 
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Joined: May 05, 2010 1:14 am
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' It effectively turns your spent fuel into early-PWR fuel in small elements.'
Sorry, EI, I don't follow you here. I know there was a proposal for burning once-through PWR fuel in Candus, but I thought if you got a high burn-up in a Gen III reactor there would be less fissile plutonium in the spent fuel, and the option of reusing it in a Candu would be less attractive. Surely high burnup fuel from a Candu would be completely useless in a light water reactor ?


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PostPosted: Feb 08, 2017 2:09 pm 
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Joined: Jun 19, 2013 11:49 am
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jon wrote:
' It effectively turns your spent fuel into early-PWR fuel in small elements.'
Sorry, EI, I don't follow you here. I know there was a proposal for burning once-through PWR fuel in Candus, but I thought if you got a high burn-up in a Gen III reactor there would be less fissile plutonium in the spent fuel, and the option of reusing it in a Candu would be less attractive. Surely high burnup fuel from a Candu would be completely useless in a light water reactor ?


I mean that the burnup approaches levels found in early LWR fuels, so would have to be stored in similar conditions.
It would produce far more heat than a typical CANDU NU fuel element.


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