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PostPosted: Aug 10, 2018 10:34 pm 
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The Bulletin of the Atomic Scientists has an interesting article regarding an opinion that there is an unappreciated proliferation risk with Protactinium. Here is the link:

https://thebulletin.org/2018/08/thorium ... m-problem/

There are several replies to the article, mostly indicating that the risk is overstated in the article.

Any comments?


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PostPosted: Aug 14, 2018 7:55 pm 
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Mikeaustria wrote:
Any comments?


Sure, none of them nice though. I'll be as diplomatic as I can to explain my view of the situation.

Any nuclear reactor has the potential to produce weapon grade material. The production of weapon grade U-233 from natural thorium is quite similar to that of producing weapon grade Pu-239 from natural uranium. To do this means using a commercial power reactor in a way that makes it impossible to produce power. A commercial power reactor that is suddenly consuming large amounts of power (because running a power plant still takes a lot of power) instead of producing it will be plainly obvious. This kind of activity has been detected from orbit using thermal imaging, such as seeing heat from the reactors but none from the turbine hall.

Building a reactor specifically for producing weapon grade material is an obvious announcement of a nuclear weapon program. A "dual use" reactor, that can be used to produce power and weapon grade material at the same time, is possible but still an obvious announcement of a nuclear weapon program. Using a reactor in this manner, to produce power and weapon grade material, will be obvious as it produces visible activity inconsistent with a reactor used only for power.

Perhaps someone could do this "underground" but that only means doing so at a rate that is difficult to detect. This will take a lot of time to produce even a single weapon. Doing this literally underground, in some kind of cavern to avoid satellite observation, is expensive and again an announcement of a nuclear weapon program.

Much of the computation on figuring this all out is probably on the level of a second year college engineering course. It is easy to find out how difficult this will become. What will become obvious quickly, and I suspect that the people that wrote this article already know, is that none of this can be kept secret for long.

This is a load of fear mongering, and to what end they wish to reach is something that boggles me. Are they trying to expose the weapon proliferation risks of nuclear power? That's been known since we've been doing nuclear power, and is a consideration of every power plant built since the end of the Cold War. Are they trying to dissuade people from using nuclear power? That will only work until someone else comes along to call their bluff.

I'm not a nuclear engineer but I know enough chemistry and physics to prove this is all nonsense. Their soapbox is just bigger than mine, therefore their word is spread more widely.

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PostPosted: Aug 14, 2018 10:53 pm 
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Kurt,

I think your reply is spot on. Nuclear fear mongering seems to be a continuing epidemic, and the public needs to be able to envision other more objective sides to these topics. Perhaps some of this Forum's readership with significant credentials could post more articles in widely read publications? There seems to be very few posts on the topic of thorium relative to uranium reactors. Some of the well-respected organizations and sites, such as thebulletin.org, and also perhaps Discovery and Smithsonian sites might be coaxed to objectively show the potential of much safer nuclear power via thorium and LFTR. Just a thought. It's very difficult to overcome years of inertia on the subject of 'Nuclear is dangerous!' that grabs the big headlines. An education 'blitz' is needed, but very difficult to get traction. Mike


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PostPosted: Aug 15, 2018 8:13 am 
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Fear always sells better than facts.

The "Bulletin" has been trafficking in nuclear fear since its inception. Hence their stupid pointless "Doomsday Clock".

These are not people who will ever give a new nuclear technology a measured, reasoned examination. They'll do something like this: find a post-doc in "proliferation studies" that can paint a veneer of credibility over what is simply fear, uncertainty, and doubt (FUD).


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PostPosted: Aug 17, 2018 2:51 am 
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I may be going off topic a bit here but I was giving this article some thought the last couple days. Assuming the separation of U-232 from U-233 was as trivial as claimed by The Bulletin would there be any reason someone might want to do so besides to produce weapon grade material? I'm assuming someone might do this to capture the U-232 for some purpose and the U-233 would be returned to the core to keep it running.

Would U-232 make for a reasonable radioisotope heat source or radio-thermal electrical generator? I know that the radiation from U-232 is, perhaps to put it mildly, problematic. How thick would the case on a U-232 based RTG have to be compared to that of Pu-238 or Sr-90? Is there a possible medical or industrial use for U-232? Such as where cobalt-60 is currently used? Maybe not U-232 itself but some decay product down the chain. Might it make some sense to remove it from the reactor to somehow improve the performance? Is U-232 considered a "poison" to keeping the reactor critical? Or, is it valuable enough as fuel that no one would want to remove it even if it cost nothing to remove?

In short, I'm just thinking of ways someone might justify introducing some kind of "filter" for U-232. This could be for completely legitimate reasons or a just an excuse that could serve as cover for a weapon program.

Another thing about this article that might be closer to the topic at hand. Looking at the comments on The Bulletin article page I find four people that commented, Peter John, Thomas Jam Pedersen, Cavan Stone, and Robert Hargraves. I recognize the names Stone and Hargraves from videos produced by Gordon McDowell. Pedersen I found with a quick Google search and I see he's done work on LFTR style reactors. The mystery is Peter John, should I know who this person is?

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PostPosted: Aug 17, 2018 7:25 am 
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232U is moderately fissile.

Indeed there is a proposal floating around to try and obtain quantities of 231Pa to use as a core life extender.
It has a 500 barn cross section so acts as a neutron poison but then turns into the moderately fissile isotope 232U, and then into the extremely fissile 233U.

That way the neutrons captured in the poison are not wasted and become available later on.


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PostPosted: Aug 17, 2018 4:53 pm 
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E Ireland wrote:
232U is moderately fissile.


Yes, I noticed that in my own research. If I'm reading these charts I found correctly there's a 50/50 chance of U-232 fissioning or capturing a neutron when smacked with one. If it capture then it's just U-233 and smacking it with another neutron has a high probability of fission with 2.3 neutrons out. So no better or worse than thorium. If U-232 is removed then makeup with thorium would be necessary, but then makeup with thorium is necessary regardless because fuel is consumed.

I guess I'm not sure what kind of answer I'm looking for. I can do much of the math myself with my sophomoric understanding of nuclear physics. One possible answer is simply that no U-232 extraction could be justified due to the risks of weapon proliferation. That's not a satisfying answer because so long as someone can find a use for U-232 then it seems to me that there could always be a justification, especially if the U-232 has considerable value for some purpose. Maybe I'm looking for a Mythbusters style "busted", "confirmed", or "plausible", kind of answer. Well, maybe I should just drop that for now and be satisfied with "it's complicated".

E Ireland wrote:
Indeed there is a proposal floating around to try and obtain quantities of 231Pa to use as a core life extender.


When thinking through a protactinium extraction on a LFTR where Pa goes into the decay tank and U comes out I thought there might be a build up of the relatively long lived Pa-231. If there is a use for this then that's great. This still doesn't justify, IMHO, the concern The Bulletin has on protactinium. I'm thinking the Pa-231 would simply be allowed to pile up in the decay tank until the reactor end of life and then be taken out. At this point there might be some possibility of someone maybe getting some teeny tiny drop of highly pure U-233 salt. That's really overblowing the problem though. If for some reason someone does raise this as a concern then I could probably come up with a half dozen ways to address this.

E Ireland wrote:
It has a 500 barn cross section so acts as a neutron poison but then turns into the moderately fissile isotope 232U, and then into the extremely fissile 233U.


Is this use of Pa-231 as a core life extender for solid fuel reactors, liquid fuel reactors, or both?

E Ireland wrote:
That way the neutrons captured in the poison are not wasted and become available later on.


My math tells me the reactor would have to put 3 neutrons in to get 2.3 neutrons back, is that about right? I guess that small loss is part of the cost in using Pa-231 as a core life extender. I believe I understand how this works, and it is very interesting. I could perhaps see this extraction of Pa-231 as a path some bad actor might use to process fuel in a way that might somehow possibly maybe with great care and lots of sleight of hand get small drops of highly pure U-233. Again, this seems easily addressed, such as simply not allowing such processing and requiring the use of other sources for Pa-231.

Near the end of the article in The Bulletin states this.
Quote:
Reprocessing creates unique safeguard challenges, particularly in India, which is not a member of the Nuclear Non-Proliferation Treaty.


A state that has not signed the NNPT has effectively announced an intention to develop nuclear weapons. I believe every nation has a right to develop nuclear weapons if they choose. Saying anything less, as an American citizen, would be hypocrisy since the USA has its own stockpile of nuclear weapons. My concern is for states that have signed the NNPT to gain favorable trade agreements with other nations only to not play by the rules they signed up for. If such states are not pleased with inspections of their "civilian" nuclear reactors then they can simply leave the NNPT.

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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 17, 2018 7:24 pm 
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Kurt Sellner wrote:
Is this use of Pa-231 as a core life extender for solid fuel reactors, liquid fuel reactors, or both?


Primarily very compact PWRs for naval and other marine uses.
The reactivity swing in a core using HEU is absolutely enormous.


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