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 Post subject: Two Fluid DMSR?
PostPosted: Mar 04, 2013 5:53 pm 
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Is it possible to have a two fluid DMSR and achieve similar levels of proliferation resistance as the ORNL single fluid DMSR?

I don't think so, but I'd like hear what others think about this.

Starting with the blanket, if you add U238 into the blanket to denature the U233 being generated, one will also be generating Pu239 and the build-up of Pu240 (degrading the Pu239) will take some time, so for some periods of time the isotopic mix of the Pu will heavily favour Pu239 which is undesirable from a proliferation point of view.

Another possible approach might be to leave U238 out of the blanket and use Th230 spiking of the blanket thorium to achieve self protecting levels of U232 decay products, but if we fluorinate the U out of the blanket (a common way of stripping out U), those decay daughters get left behind in the blanket and the stripped material is no longer self-protecting as per the IAEA definition.

I haven't put a lot of thought into it, but I don't think it can be done without including measures that could be circumvented with relative ease, making the single fluid DMSR design superior on the proliferation resistance scorecard. I would be very happy to be proved wrong.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Mar 04, 2013 8:50 pm 
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Seems like you would want to start with both the fuel and blanket salts pretty radioactive - otherwise you have decently pure plutonium 239 reasonably accessible for the first 3 months of operation (for the fuel salt). For the blanket, I could distill the salt and then add a fresh load of thorium (same story with thorium spiked with 230Th). Assuming thorium is reasonably accessible it seems like one could generate fairly pure u233 this way. If you spike the blanket with 238U I just distill the blanket salts to grab the FLiBe and then add thorium and I'm back in business.

Allowing a modest continuous flow of fission products from the core to the blanket would help thwart this plan.

But allow the proliferator access to a fluorinator and he can first exchange the blanket heavy metal, then run the reactor for months and then pull the 233U out from the thorium.

But for that matter I can do the same with an LWR if I make my own fuel rods and put the thorium rods on the outer perimeter.

DMSR is tougher to defeat and provides stronger proliferation resistance IF you ignore the proliferation risks associated with increasing demand for enrichment services.

The DMSR is what you get if you make all tradeoffs to prevent proliferation technically. In the process you do end up requiring enrichment services over the long haul. Also, you get spent fuel that is still enriched but not suitably to recycle into the DMSR. A DMSR only plan would need to explain what the plan is for this spent fuel. Very few enrichment services companies want to deal with enriching spent fuel.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Mar 05, 2013 2:51 am 
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Using both thorium and uranium is a very good idea which need not be wasted on the prime consideration of denaturing the U-233 created.
The core fluid could be initially 20% LEU as molten salts, diluted to the extent necessary with inert salts. U-238 fission will provide additional neutrons.
Thorium can be used in two ways. Firstly as metallic rods in the blanket. Secondly as metallic rods dipped in the fuel to reduce the fissile content proportion to the desired level. These could be reduced or increased .and also raised or lowered to meet the reactivity control requirement. The liquid fuel can be burned to the maximum till the fission products allow. The thorium should be frequently replaced to optimize the U-233 creation. U-233, recovered by electrolytic refining, can be used to make up the fissile depletion in the core or in new reactors as fissile feed. Metallic thorium in a separate phase replaces the second fluid as the blanket without the need for a wall. Clean salt can be used as the coolant in a heat transfer coil in the core.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Mar 05, 2013 2:43 pm 
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I wonder if your concern about diversion is misplaced even though I understand your concern. We do not want to hand bomb making materials to a terrorist. As Lars said, in the long term we think side reactions produce enough gamma emitters to preclude successful diversion. We can add those isotopes from the start. At some point you have to ask why. Public relations and international standards of deterrence to diversion is a fine answer. We need to make diversion difficult, not impossible.

Given enough money, you can buy natural uranium, heavy water, or graphite. Given enough money, you can run a plutonium production reactor that is designed to produce bomb grade isotopes without subsequent isotope separation.
My point being that good enough is good enough. How close are we to good enough?

Am I missing something.

_________________
It is good to be splitting atoms again on the weekend. :wink:


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Mar 05, 2013 4:04 pm 
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Those are interesting points and valid questions, but the original question is a technical one separate from those.
Quote:
Is it possible to have a two fluid DMSR and achieve similar levels of proliferation resistance as the ORNL single fluid DMSR?


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 23, 2014 12:34 am 
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Lindsay wrote:
Is it possible to have a two fluid DMSR and achieve similar levels of proliferation resistance as the ORNL single fluid DMSR?
{snip)
I haven't put a lot of thought into it, but I don't think it can be done without including measures that could be circumvented with relative ease, making the single fluid DMSR design superior on the proliferation resistance scorecard. I would be very happy to be proved wrong.


I agree Lindsay with your original contention that single fluid DMSR is easier to design to have excellent strong proliferation features.
The DMSR that Dr. Dick Engel describes in ORNL/TM7207 is actually single-fluid two-region DMSR and separates the highly radioactive core salt region from the secondary cooling salt region that ultimately transfers heat to the turbine-generator power block. Single-fluid Two-region DMSR should have fewer material uncertainties (no two-fluid inner wall materials problems) and should be quicker and easier to economically manufacture. The Single-fluid Two-region DMSR described in ORNL/TM7207 has the additional advantage of not requiring a chemical support plant and was designed to operate for 30 years without removing fission products or contaminants (other than fission product gases with the off-gas system).


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 23, 2014 2:36 am 
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In the best two fluid DMSR, the second fluid could be a plain coolant salt. It will render it un-necessary to take out the fuel except for removal of fission products in a non-proliferating manner like crystallization of some fission products and making up of fissile, as and when necessary.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 23, 2014 10:49 pm 
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jagdish wrote:
In the best two fluid DMSR, the second fluid could be a plain coolant salt. It will render it un-necessary to take out the fuel except for removal of fission products in a non-proliferating manner like crystallization of some fission products and making up of fissile, as and when necessary.

This is the essence of the German DFR concept: http://dual-fluid-reactor.org/

.....except that they propose to use lead instead of molten salt as the coolant.

The big problem with the DFR and similar ideas is heat transfer from the quasi-static fuel -- as has already been discussed a number of times in other threads on this forum.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 3:25 am 
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The fundamental problem, as I see it, is that you have to move fissile from the blanket to the core. For LEU you can fluorinate, but if you do that once and then stop adding U238, from that point on you're making pure U233 in the blanket. So you have the fluorinator onsite since you need it, that means you have the means for proliferation.

Then there's plutonium which is nigh on impossible to transfer to the core fluid, and if you could find a way, then that's another proliferation path (as above but with WGPu rather than HEU).

This means that any two fluid will not be acceptable to the anti proliferation people.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 9:09 pm 
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Sorry, but I refuse to accept the notion that any nuclear fuel approach that relies on uranium enrichment is somehow "superior" from a proliferation standpoint to plutonium or uranium-233. Just stop and think about it for a minute.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 9:36 pm 
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Kirk Sorensen wrote:
Sorry, but I refuse to accept the notion that any nuclear fuel approach that relies on uranium enrichment is somehow "superior" from a proliferation standpoint to plutonium or uranium-233. Just stop and think about it for a minute.

How about superior from a policy compliance standpoint? ....is non-compliance a viable strategy for a prospective NPP design ?


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 9:56 pm 
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It seems to me that in regards to proliferation concerns, the argument for the DMSR is that enrichment is something that is presumably carried out in a highly visible, centralized facility subject to intense scrutiny by regulators (e.g. current Iran situation), the IAEA, whoever. Any 2-fluid reactor that extracts HEU or Pu from a blanket fluid will have distributed the proliferation concern out to the reactor sites. If I am worried about proliferation and imagine a future with lots of small, 2-fluid LFTRs distributed across the world, I am going to wonder how all those reactors with their integrated chemical processing capabilities are going to be controlled and monitored. I am going to be worried about someone secretly modifying an installation somewhere to enable Pa sequestration and the generation of high purity 233U, for instance.

In addition, the enrichment industry already exists, so we understand the proliferation concerns surrounding that. LFTRs raise new questions and risks, which are always scarier than risks we've grown to live with.

Disclaimer: I'm all in favor of LFTRs and DMSRs. I'm just trying to understand what some of the political/societal challenges are going to be.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 10:11 pm 
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Ah, the descent into infinite proliferation arguments begins...

Meanwhile, in the real world, we burn coal and oil and gas...and any two-bit dictator who wanted to proliferate would enrich uranium or make plutonium from a uranium-graphite reactor.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 10:45 pm 
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Kirk Sorensen wrote:
Ah, the descent into infinite proliferation arguments begins...

Meanwhile, in the real world, we burn coal and oil and gas...and any two-bit dictator who wanted to proliferate would enrich uranium or make plutonium from a uranium-graphite reactor.


Well, I just think it is going to be much easier to sell the idea of a countryside dotted with sealed DMSRs running on LEU than 2-fluid MSR breeders which produce HEU. That's the contrast that the anti-nukes will see and use, regardless of the nitty gritty details. Any breeder design need to address this concern somehow.

Just MHO.


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 Post subject: Re: Two Fluid DMSR?
PostPosted: Feb 24, 2014 10:56 pm 
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You're just shifting the concern to another place. With DMSR you still have to ship enriched uranium to the site and spent fuel away. No real improvement over today's arrangement.

Anti-nukes oppose all forms of nuclear energy, regardless of the fuel cycle. You'll never please them.


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