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PostPosted: Aug 27, 2016 2:56 am 
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Kiteman,
In my speculation above on how your proposed 2.2+ fluid LFTR would work I did a lot of hand waving over details, mostly for brevity but also because I don't understand the chemistry completely. In thinking some more on how it might work and how to improve the Np-237 purity I realized that it is quite possible I stumbled across a MSR variant that can produce weapon grade plutonium. Perhaps you didn't make this realization. Perhaps you have come up with a different process that does not have this problem.

I don't want to go into the details on how this MSR could produce weapon grade plutonium as this is not the forum for such speculation. However, I am interested in discussing your proposal further if your design does not have the weapon proliferation problem that I speculate it does. If you start another thread about the design details of your proposed reactor then I'll join you there to discuss further.

What do you think?

Edit to add: Mr. Sorensen, I have rephrased the following questions to you in a following post based on Mr. Meyer's comments, please ignore them here. Thanks.
Mr. Sorensen,
Do you have a problem with us discussing this design further in another thread? I'm assuming you can derive the weapon proliferation problems I've alluded to. Perhaps you've seen something like this before and would like to comment?

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


Last edited by Kurt Sellner on Aug 27, 2016 7:06 pm, edited 1 time in total.

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PostPosted: Aug 27, 2016 11:09 am 
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Wow, Kurt. Thanks. That's a bit to study. I'm glad you took the time to write this. I'm glad I could help with the link to Lars.

Is the real question here if our forum host cares for such thought experiments? He already cited "angels dancing on the heads of pins"—so once again, I cringe. He already threatened to shut this forum down for such. I hope he doesn't. (Hi, Kirk! Please don't shut down the forum.) But in you and KitemanSA having this discussion, his answer was already no. I cringed at your request for his comment in your question again to KitemanSA. He's being lenient, don't you think? Is it wise to push it?

As long as we're still here, I thank you, Kurt, for sharing your Iowa background here. I think it's great. I value my learning experience on Kirk's forum—thank you, Kirk.

On topic: I would love to read your assessment of the FE LFTR in your thought experiment scheme; focus on the precise goals of FE LFTR. Even if it's redundant. So I apologize. Do you own a copy of the October 2015 EPRI Program on Technology Innovation: Technology Assessment of a Molten Salt Reactor Design—The Liquid-Fluoride Thorium Reactor (LFTR)?

After all, if our kind and generous EFT host who is the LFTR developer has but one mission, then I would think that posts on this forum, out of respect for the man and his sacrifices and achievements, ought to always relate to his goals. He's made clear he isn't interested in but one design. But knowledge in many areas has a bearing on his work. I suppose a form of occupational hazard.

In studying his machine, I image the optimum design would have total control over all isotopes in each of the two salt streams so it is an optimum U-233 breeder. So isn't it that to start it up for the first time, one wants as pure an initial U-233 inventory as possible? If yes, then this topic ought to be focused strictly on how to achieve that goal.

Given the last point, if a "pure" U-233 start up inventory is desirable and achievable, then I was interested in this topic to know if in particular the SRS mission could be changed to focus on employing the 35–37 tonnes of WG Pu there to get that job done. Plus, if the SRS MOX facility gets completed for supplying the U.S. utilities and their fleet of operating LWRs, could that mission be expanded for supplying LFTR U-233 start up loads?

I want to promote this energy technology to regular voting citizens. To do that, I must fight my deficient brain and learn how to sell the program. Maybe I could think clearer if the angels would stop dancing on my head.

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PostPosted: Aug 27, 2016 7:03 pm 
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Tim,
I have downloaded and read the EPRI document you have linked to in your post. As it is a lengthy document I did not re-read it today but instead did some keyword searches and re-read portions. In that document there is little mention of fuel used for startup. There is mention that it is assumed suitable startup fuel will be available, I did not see mention of what constitutes suitable startup fuel, which is the question posed by Alex P. The EPRI technical report does state that addition of U-238 would be detrimental to the efficiency of LFTR operation, and would contribute to the TRU waste problem.

I am confused on if the presence of U-232 in the LFTR salt is in sufficient quantity and so forth to meet the legal definition of being a denatured fuel. As I've seen news articles of the federal government considering down blending their stockpile of U-233 with DU as a means of disposal I have questions on what constitutes a weapon proliferation risk. From what I've read I conclude that U-233 in the absence of U-238 is legally a weapon grade material or that this government stockpile is of a different isotopic composition than that from LFTR. If there is a government imposed requirement that U-233 used in civil power reactors be denatured with DU then we will see the problems indicated in the EPRI technical report. In doing my own back-of-the-envelope analysis of this I see an additional problem of weapon proliferation issues and Np-239 contamination if one is attempting to do Np-237 extraction from a LFTR. The EPRI report does not mention the possibility of Np extraction from LFTR, and adding U-238 as fuel was not considered, therefore the weapon proliferation issue I foresee does not come up.

I went through my thought experiment here for several reasons. One of them is to demonstrate to Alex P and others the relationship between fuel choice and reactor design. I also did so to encourage socratic debate as I wish to clarify the details and compromises made for the different variations on the MSR theme.

I will also comment (at the risk of opening old wounds) that the EPRI report makes the distinction between LFTR and LiFR (pronounced "lifer"?) or Liquid Fluoride Reactor. LFTR uses molten fluoride salts as a carrier for thorium fuel. A reactor that uses molten fluoride salts as a carrier but a fuel other than just thorium, such as LEU, is a LiFR. All LFTRs are LiFRs but not all LiFRs are LFTRs. I used the term TMSR in my thought experiment so as to include ThorCon, which proposes NaBe salts as a possible alternative to fluoride salts, and DMSR, which burns LEU.

I understand your concern to leave such open ended questions to our host. I will rephrase the questions.

Mr. Sorensen,
In my thought experiment to discuss the startup fuel concerns from Alex P and the proposed reactor design from Kiteman I believe I have discovered a weapon proliferation concern when fueling LFTRs with U-238, especially when Np extraction exists on the reactor. As an experienced nuclear engineer I expect that you have done a similar analysis. Do you share my weapon proliferation concerns? Also, I would like to continue my discussion with Kiteman on his proposed reactor design. Would you prefer we continue this discussion in a different thread within this forum, or in a different thread on a different forum? As Kiteman has pointed out the reactor is a thorium breeder and should fit within the goals of this forum, if you disagree then I'll ask that you state your preferences to Kiteman and I'll follow his lead.

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PostPosted: Aug 28, 2016 12:49 am 
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Kurt Sellner wrote:
Kiteman,
In my speculation above on how your proposed 2.2+ fluid LFTR would work I did a lot of hand waving over details, mostly for brevity but also because I don't understand the chemistry completely. In thinking some more on how it might work and how to improve the Np-237 purity I realized that it is quite possible I stumbled across a MSR variant that can produce weapon grade plutonium. Perhaps you didn't make this realization. Perhaps you have come up with a different process that does not have this problem.

I don't want to go into the details on how this MSR could produce weapon grade plutonium as this is not the forum for such speculation. However, I am interested in discussing your proposal further if your design does not have the weapon proliferation problem that I speculate it does. If you start another thread about the design details of your proposed reactor then I'll join you there to discuss further.

What do you think?
Interesting. I am not sure how you would do it.

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PostPosted: Aug 28, 2016 9:21 am 
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Thank you, Kurt, for looking through your EPRI LFTR copy. I'm studying it, too, for those points. Seems you're highlighting the "pathway to plutonium production (PPP)" for the proliferation risk criterion. That is illuminating. I wish you would have been nuclear Navy instead. If I would have known in 1980 what I know now, I would have done my education differently.

KitemanSA: You answered Kurt's question(s) that you did not know. To you and Kurt (anyone?), there was a time in the beginning of this forum when Dr. Le Blanc, Lars, Kirk, Cyril, and I'm not sure on any others here with experience in nuclear work who discussed such details. Too bad that isn't happening anymore.

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PostPosted: Aug 28, 2016 12:38 pm 
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Kurt Sellner wrote:
Tim,

I am confused on if the presence of U-232 in the LFTR salt is in sufficient quantity and so forth to meet the legal definition of being a denatured fuel. As I've seen news articles of the federal government considering down blending their stockpile of U-233 with DU as a means of disposal I have questions on what constitutes a weapon proliferation risk. From what I've read I conclude that U-233 in the absence of U-238 is legally a weapon grade material or that this government stockpile is of a different isotopic composition than that from LFTR. If there is a government imposed requirement that U-233 used in civil power reactors be denatured with DU then we will see the problems indicated in the EPRI technical report. In doing my own back-of-the-envelope analysis of this I see an additional problem of weapon proliferation issues and Np-239 contamination if one is attempting to do Np-237 extraction from a LFTR. The EPRI report does not mention the possibility of Np extraction from LFTR, and adding U-238 as fuel was not considered, therefore the weapon proliferation issue I foresee does not come up.
Kurt,

This forum has: Board index » General Nuclear Discussion » Safety, Security, Proliferation. It runs for four pages of topics. Four of them have "Proliferation" in their titles. I will wait and see if you create a new topic there with "Proliferation" in the title reviewing uranium-232 pealed off from this fruitful topic on fissile start up in a LFTR.

Again, this topic is a nexus subject not the least of which is a new U.S. national priority for new nuclear development and deployment and on fluid-fueled (molten salt) reactor designs in particular especially in regards to thorium for our nation's next nuclear fuel cycle.

Directly to Kirk with respect to earlier talks years ago on the U.S. government's stance on new reactor development now resting with the industry to be negotiated with the utilities does not seem workable. Competition with the installed solid-fueled fleet and growing production and use of natural gas, and severe regulatory uncertainty, the new administration and congress could direct and fund the DOE to recognize and support a restart for the original ORNL Weinberg MSBR program especially with respect to starting the thorium fuel cycle. Russian President Putin is supposed to have a thorium report in March 2017. Maybe that with become a Sputnik moment?

Kurt, the EPRI LFTR tech assessment on "uranium-232" in section three, 3.4.1 Requirements has:
Quote:
10. The reactor fueled by thorium shall employ core design arrangements that maximize the production of uranium-232 and its precursors in order to minimize the appeal of any fissile material for diversion away from power production.

Basis: the presence of uranium-232 and its gamma-emitting decay products does not compromise the power-generating performance of the reactor but reduces the attractiveness of the isotopic mixture of uranium for diversion to other activities.
3.4.2 Bases of Design has:
Quote:
10. Through careful arrangement of fuel, blanket, and moderator structures, fast neutrons from fission can be given greater opportunities to generate uranium-232 and its precursors in both the fuel and blanket fluids, satisfying the objective of requirement #10. Intentional introduction of thorium-230 into the blanket is another option, but this isotope is rare and may be difficult to procure.

11. In a one-fluid reactor, thorium-229 would be utterly lost in the large amount of natural thorium-232 present, and would not be extractable. A two-fluid reactor that keeps thorium-232 out of the fuel salt can satisfy requirement #11. Requirement #10, maximizing uranium-232 production, leads to thorium-228 formation from uranium-232 decay. But this problem can be mitigated by the removal of the actinium, since actinium-225 forms from the decay of thorium-229 but no actinium forms from the decay of thorium-228.
Wikipedia has that thorium-229 decays by alpha emission with a half-life of 7340 years, and its principal use is for the production of the medical isotopes actinium-225 and bismuth-213.

3.4.3.2 Subsystems and Major Components has:
Quote:
The chemical processing system would remove protactinium and uranium from the blanket salt and hold it for sufficient duration in the decay salt to permit protactinium-233 and protactinium-232 to decay to uranium-233 and uranium-232. The uranium would be fluorinated from the decay salt and added to the fuel salt. Fuel salt would be chemically processed to remove fission products via reductive extraction by lithium into bismuth. Further processing of the bismuth is anticipated but not described at present. Thorium-229 would be present in the bismuth in economically attractive quantities.
Targeted alpha therapy evidently is showing real promise for actually curing cancers! Also, I was disappointed the expected bismuth processing didn't make it into the document. I want to know more about the liquid-liquid molten bismuth reductive extraction performance at a more lay level.

But your original concern is if the authorities will accept FE LFTRs proposal for anti-proliferation by uranium-232. In the U.S., UK, IAEA, and other nuclear laws, this must be determined.

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PostPosted: Aug 28, 2016 8:11 pm 
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I will start and end this post with a disclaimer: I have done some calculations here which may be incorrect. As these calculations are relatively trivial for most anyone with a high school or first year college level knowledge of chemistry and physics I don't feel like I'm stating anything that can be considered any more dangerous than a college textbook. If I've made a gross error somewhere I would appreciate a correction.

Tim,
You are correct to point out that there is a portion of this forum dedicated to proliferation concerns. If we were to discuss the proliferation concerns of Kiteman's 2.2+ fluid LFTR further then we should take it there. I'm not going to discuss that further here except where it overlaps with the questions Alex P brought up. As you point out the U-232 content of the LFTR salt should prevent it's use in a weapon, my question is if that U-232 content is enough to be considered not weapon grade under the current law. That is a question best discussed elsewhere.

Kiteman, Alex P, et al,
The question is, can one start a LFTR with something other than U-233. The answer is yes but in certain cases you would not want to do so. I'll go through another thought experiment to clarify my earlier points.

In the case of a LFTR that has no means to extract Np there are no concerns of a poor quality Np product, or proliferation concerns since the salt taken from the reactor for reasons of removing fission products will have enough isotopic variety that it's worthless for weapons or Pu-238 production. In that case the only concern left is the ability for the starter fuel to start the reactor and not interfere with the breeding. U-238 is something to be avoided as it has poor properties in a thermal reactor but as it something that is inherently present in LEU, and LEU is something that can be easier to obtain than reactor grade U-233, then the presence of U-238 may have to be tolerated. As pointed out in the EPRI report the adding of U-238 to a LFTR after the reactor has started should be unnecessary and is detrimental to its operation. Starting a LFTR with reactor grade plutonium may be acceptable, I have not seen a reason to avoid it in my thought experiments but there may be reasons to avoid it that I have not encountered.

In the special case of a LFTR that has Np extraction the addition of any U-238, even as starter fuel, can have other concerns. U-238 will become Np-239 after grabbing a neutron and a few minutes of decay. If doing a continuous extraction of Np, which is necessary to get a high quality Np-237 from the neutron bombardment of thorium, then that Np-239 will come out as well. Because the amount of thorium that ends up as Np is something like 2%, and the amount of U-238 that ends up as Np is nearly 100%, the Np that comes out is going to be dominated by Np-239.

Np-239 will decay into Pu-239 in a matter of days. The Np isotope we want, Np-237, has a half life of over a million years. Every other isotope is unlikely to show up in the Np extraction due to properties like very very short half lives, high probability of fission, and high probability of neutron capture. From here it is trivial to extract weapon grade plutonium. This is going to be a regulatory nightmare for any power plant in most any nation. To avoid this problem the U-238 must be kept from the fuel except in the most minute ratios, Np extraction must not be permitted, or some other safeguards must be in place to make sure the plutonium ends up back in the fuel.

What Np extraction does do is allow for continuous production of weapon grade plutonium if there is a significant ratio of U-238 in the fuel. A LFTR with U-238 in the fuel can still produce weapon grade plutonium in a batch process. This is much like how it is done in a solid fuel reactor but lacking the expensive fuel fabrication steps. I'll leave the details as an exercise for the reader.

I will start and end this post with a disclaimer: I have done some calculations here which may be incorrect. As these calculations are relatively trivial for most anyone with a high school or first year college level knowledge of chemistry and physics I don't feel like I'm stating anything that can be considered any more dangerous than a college textbook. If I've made a gross error somewhere I would appreciate a correction.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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PostPosted: Aug 29, 2016 4:51 am 
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I came across something that should better quantify the value of the various fuels under discussion. I found a graph on the Candu Owners Group website (candu.org) that gives the k-factors of U-233, U-235, and Pu-239 compared to neutron energy.

In the thermal spectrum we have the approximate numbers:
U-233 -> 2.2
U-235 -> 2.1
Pu-239 -> 2.0

Depending on how you want to interpret these numbers this could mean the fuels are nearly equivalent to making plutonium look really bad.

Since we are talking about starter fuel, and how U-238 can affect fuel quality we need to take a couple of those numbers, subtract one for the breeding, another to account for fission, and take off a small percentage to account for losses. With that we get the net gain which looks something like:
thorium -> 0.15
U-238 -> -0.05

This shows U-238 as a minor neutron poison. With LEU being a mix of a small portion of U-235 and larger portion of U-238 this must be considered.

With U-233 the primary contaminate would be U-232. I find out that U-232 when it captures a neutron roughly half the time it fissions, and the other half becomes U-233. At that point it behaves like any other U-233, a high rate of fission, and a low rate of capture. Assuming that U-232 fission produces more than two neutrons we should see something near break even like U-238, or better. As the portion of U-232 contaminate in U-233 is relatively small that makes reactor grade U-233 a better quality fuel.

Reactor grade plutonium can have a number of impurities, denaturing elements, and isotopic ratios depending on it's source and such. With these variables I find it difficult to estimate what the effective neutron gain from reactor grade plutonium might be. I may find this later but if someone is willing to search this out then I 'd appreciate that.

This gives some more information on why U-233 is preferred than any other fuel. I believe it also demonstrates the reason India has decided to take the three stage approach to LFTR. There does appear to be a parallel effort to skip the second stage, in their three stage program to get LFTR. First stage is U/Pu MOX breeders, they are to produce more plutonium for the metal fuel fast breeder reactors. The second stage is to breed U-233 from plutonium in a fast breeder. I'm guessing this allows for more neutrons from the plutonium fission while reducing the chances that the U-233 fissions. This should produce more U-233 than the parallel effort that is using a thorium/uranium MOX in a heavy water thermal reactor. Skipping the fast breeder step may save time.

What I do not see India proposing is starting their LFTRs with anything other than U-233. I am confused a bit on why India does not consider using existing stock of their Pu to start a LFTR. Perhaps it will become clear in the future.

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