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PostPosted: Dec 13, 2013 12:00 pm 
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Lars wrote:
So you are presuming the turbine working fluid is helium and we need to spend the R&D to develop the turbine. OK, but that will slow down the deployment of first units.


I'm an agnostic wrt which working fluid is used to drive the turbines. However, it does seem reasonable to use something other than water if tritium leakage is deemed to be exceedingly important. From what I've gathered either CO2 or He would work fine in the turbines (better than water) & removing tritium from either shouldn't be difficult.

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PostPosted: Dec 13, 2013 12:12 pm 
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darryl siemer wrote:
Lars wrote:
So you are presuming the turbine working fluid is helium and we need to spend the R&D to develop the turbine. OK, but that will slow down the deployment of first units.


I'm an agnostic wrt which working fluid is used to drive the turbines. However, it does seem reasonable to use something other than water if tritium leakage is deemed to be exceedingly important. From what I've gathered either CO2 or He would work fine in the turbines (better than water) & removing tritium from either shouldn't be difficult.


It may be easier at first to just go with an off-the-shelf steam turbine, and use a nitrate salt intermediate loop. The nitrate salt heat transfer loops are available commercially, so this is a "no new technology" option for a first build. I'm a bit put off by the development cost and timelines of succesful new power cycles. Helium turns out to be a tricky leaky gas, and some weird issues with the lightness of the element wrt turbine tip speed (or something, don't recall what it was). CO2 is a much "easier" working fluid in that sense, but it has the issue of crazy mass flow rates in a small space. Imagine formula 1 engine in a shoe box. SCO turbine/compressor is even worse than that.


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PostPosted: Dec 13, 2013 1:02 pm 
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darryl siemer wrote:
I'm an agnostic wrt which working fluid is used to drive the turbines. However, it does seem reasonable to use something other than water if tritium leakage is deemed to be exceedingly important. From what I've gathered either CO2 or He would work fine in the turbines (better than water) & removing tritium from either shouldn't be difficult.

Both would imply a >$1B development effort for the turbine with significant risk.

Steam based turbines provide a solution with equivalent efficiency, near zero R&D, but higher production cost. But we need to solve the tritium problem then. The baseline plan would use a second HX loop salt that traps the hydrogen and a coating on the secondary HX on the steam side that is an effective block to tritium.


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PostPosted: Dec 14, 2013 1:53 pm 
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darryl siemer wrote:
I'm trying to ball park how much extra it would cost to make a MSFR's "barrier" out of nickel that doesn't have much 58Ni in it.


Could the same principle be applied to tungsten? On page 10 of the paper tungsten is listed as already being enriched by Urenco.

In this paper on page 12 http://hal.archives-ouvertes.fr/docs/00 ... 9-MSFR.pdf the transmutation of tungsten is cited as being one of the limiting factors to the lifetime of the axial reflectors of the Grenoble MSFR.


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PostPosted: Dec 16, 2013 11:37 am 
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Dear Burhard,

...Could the same principle be applied to tungsten? On page 10 of the paper tungsten is listed as already being enriched by Urenco....

Well isotope enrichment is very expensive and at the end it is to compete with LWR and coal fired power plants.

From my point of view it is to minimize costs whenever possible.

Holger


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PostPosted: Dec 16, 2013 2:24 pm 
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Cyril R wrote:
...


The key problem with a nitrate salt intermediate loop is that "solar salt" decomposes rather quickly at temperatures higher than about 580 C. see http://www.iea-eces.org/files/annex_19_ ... 7-2010.pdf

I'm also put off by what it would cost to actually implement any of the "advanced" heat-to-mechanical energy systems that some of US DOE's engineering experts have been paper-studying for decades. However, I also expect that those estimates are extremely "conservative" (high) because it's assumed that it'd have to be done in the same working environment that they've/we've become too accustomed to. If a CO2-based system is intrinsically cheaper to implement than is a steam based system, the Chinese will work out the details & make it happen.

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PostPosted: Dec 16, 2013 6:02 pm 
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Who says we need more than 580C in the nitrate salt? A 540C steam temperature is just fine so we don't need a hotter salt. In fact, I consider all this "must have higher temperature" to be engineering allure nonsense. Higher temperature means much faster deterioration of materials (creep, irradiation assisted creep, corrosion, etc.). At no significant gain in efficiency.


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PostPosted: Dec 16, 2013 8:20 pm 
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Cyril R wrote:
Who says we need more than 580C in the nitrate salt? A 540C steam temperature is just fine so we don't need a hotter salt. In fact, I consider all this "must have higher temperature" to be engineering allure nonsense. Higher temperature means much faster deterioration of materials (creep, irradiation assisted creep, corrosion, etc.). At no significant gain in efficiency.

While I agree with the gist of your comment, I'm also thinking that there may be some value in higher PHT circuit temperature:

If you think of temperature as voltage, then a reduced current -- less fuel salt outside the core -- will get you the same heat transfer to the secondary circuit.
Similar advantages are to be had in the ultimate heat sink (steam condensers in case of Rankine cycle), where a higher heat rejection temperature means smaller equipment at that end (albeit at the cost of overall conversion efficiency, in this case).

Minimizing out-of-core fuel salt inventory is important for both safety/operability as well as cost reasons.


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PostPosted: Dec 16, 2013 8:32 pm 
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jaro wrote:
Cyril R wrote:
Who says we need more than 580C in the nitrate salt? A 540C steam temperature is just fine so we don't need a hotter salt. In fact, I consider all this "must have higher temperature" to be engineering allure nonsense. Higher temperature means much faster deterioration of materials (creep, irradiation assisted creep, corrosion, etc.). At no significant gain in efficiency.

While I agree with the gist of your comment, I'm also thinking that there may be some value in higher PHT circuit temperature:

If you think of temperature as voltage, then a reduced current -- less fuel salt outside the core -- will get you the same heat transfer to the secondary circuit.
Similar advantages are to be had in the ultimate heat sink (steam condensers in case of Rankine cycle), where a higher heat rejection temperature means smaller equipment at that end (albeit at the cost of overall conversion efficiency, in this case).

Minimizing out-of-core fuel salt inventory is important for both safety/operability as well as cost reasons.

There is no concern with out-of-core with the nitrate salt since this is the secondary salt and it is all out of core. Second, the critical item is the change in temperature not the temperature itself. The temperature drop from primary to secondary is going to be high due to tradeoffs with out of core volume. For the temperature drop from secondary to the steam though we do not have that limitations and it becomes a cost tradeoff where a larger HX results in a lower temperature drop into secondary -> steam.


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PostPosted: Dec 16, 2013 10:29 pm 
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Lars wrote:
There is no concern with out-of-core with the nitrate salt since this is the secondary salt and it is all out of core.

Very true. Sorry about the confusion: The secondary circuit may indeed run at MUCH lower temperature than the PHT.


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PostPosted: Dec 17, 2013 6:59 am 
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The nitrate salt is actually the third salt.

Its ok that you have lower temperature here; in fact, it allows a higher temp drop across the HXs, making them smaller.


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PostPosted: Jul 20, 2014 4:42 pm 
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The paper for which I've already posted several drafts has been reviewed/accepted by a technical journal.

The "FINAL" version I'm attaching incorporates the suggestions made by the Editor & formal reviewers. I'd like to send it back to the journal tomorrow but would feel better about doing so if my EFT colleagues & teachers looked it over first. Please let me know if you can spot any more boo boos. (It's an admittedly opinionated opinion piece so please restrict your advice/comments to technical stuff.)

Thanks.


Attachments:
BEST MSBR final ESR revised.doc [812.5 KiB]
Downloaded 163 times

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PostPosted: Jul 20, 2014 11:33 pm 
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Fast MSR is the best way I can think of to reduce costs and recycle the used LWR fuel. However 99.995% 7Li may create some problems of procurement. An alternate salt like NaF or NaF-ZrF4 eutectic would be a better choice and material balances should be worked out.


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PostPosted: Jul 21, 2014 4:47 am 
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A few textual glitches in your paper Darryl-
No definition of 'CR' .
Below fig 5 ' ..in order to facilitate Pu breeding fertile-free TRU burning..' is confusing; perhaps ' ..to facilitate fertile-free Pu burning to get rid of TRUs..'
Below ' III. REASONS WHY THE MSFR IS THE 'BEST' GEN IV REACTOR ' - ' ...Refsgive..' needs a space.
' ..would add a small stream of helium bubbles..' should continue '.. to the salt..'
Below figure 8 some text is missing before ' ..the UF6 back to UF4.'
Below IV.A ' the US federal government- a signator..' should read '.. signatory..'

I'm unqualified to criticize the content but it seems pretty cogent to me.


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PostPosted: Jul 21, 2014 8:51 am 
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jon wrote:
A few textual glitches in your paper Darryl-
No definition of 'CR' .
Below fig 5 ' ..in order to facilitate Pu breeding fertile-free TRU burning..' is confusing; perhaps ' ..to facilitate fertile-free Pu burning to get rid of TRUs..'
Below ' III. REASONS WHY THE MSFR IS THE 'BEST' GEN IV REACTOR ' - ' ...Refsgive..' needs a space.
' ..would add a small stream of helium bubbles..' should continue '.. to the salt..'
Below figure 8 some text is missing before ' ..the UF6 back to UF4.'
Below IV.A ' the US federal government- a signator..' should read '.. signatory..'

I'm unqualified to criticize the content but it seems pretty cogent to me.



Thanks much Jon.

My third footnote defined CR - no change
I've added a comma after "breeding" .
I've put the space in
I've added "to the" before salt
I've deleted "the UF6 back to UF4" (for some reason it had ended up in the text as well as in the footnote)


Thanks again, you are a great proof reader.

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