Energy From Thorium Discussion Forum

Either LFTRs are more proliferation resistant than LWRs, for power generation or they're not. If they aren't, we should stop saying it.

'Anonymous' in this comments thread - http://lftrsuk.blogspot.co.uk/2012/07/o ... 2692951417 - is far more knowledgeable about the subject than I am and his arguments seem pretty persuasive. A couple of hundred thousand, power-generating LFTRs dotted around the globe, capable of producing "the sweetest, purest bomb-making material the world has ever known", looks a pretty scary proposition to me.

Is he/she right? - "The claim that thorium / LFTR technology is intrinsically proliferation resistant is not merely untrue, it's the very opposite of the truth!"

The answer is-Less so than fire.
Fire is dangerous and takes a lot of lives and causes damage to property. There are fires over the USA causing damage.
https://www.google.co.in/search?hl=en&g ... .6.0.3.3.0.
Yet we have fires in every kitchen and every body and his/her little son or daughter handles it.
By comparison, nuclear devices are handled by experts. There have been no deaths by nuclear plant accidents since Chernobyl.
The only time a nuclear device was maliciously used to kill people was in 1945. It was custom made for the purpose. Others have since made nuclear explosive devices to keep up with Uncle Sam. Mohammedan Extremists are the only ones (besides the US) whose declared purpose of building these devices is domination of others.
Energy demand is a very serious requirement of good life. Why should the first five's preoccupation to keep their collective privilege stop others from developing their energy resources? Why should the US give up chance to re-use the nuclear fuel in the hope of expecting others to follow them? Do they want to starve others of uranium for this purpose?

Separating Pa from Thorium will not stop the gamma emmisions of U-232 and its daughters. You need to separate Pa-232 from Pa-233. Its a small number of neutron collisions with Thorium-233 which releases another neutron. Only very special reactors avoid the Pa-232 production.

Please keep in mind while the question is simple, the answer is quite complex since the two systems are very different (and even the definition of LFTR is a challenge). I am no proliferation expert (the real ones tend to say little) but in the years I've looked at that question I still have no clear answer in my mind except that both LWRs and LFTR can be made with very low proliferation dangers (and at some point you have to start to ask, do we also shut down every pharmaceutical company on earth since in theory they have the technological capability to produce weapons of mass destruction). LWRs and LFTRs are hard to compare head to head, I'd personally give the anti-proliferation resistance edge to LWRs on the site itself but then LFTRs can help lower the need for enrichment facilities worldwide which helps swing back the balance (again my non-expert opinion).



In my opinion LFTRs do not have a clear anti proliferation advantage over LWRs so YES we should stop saying it. Not that many are making such claims but I agree some of the worst offenders are making outrageous statements that are in no way helping. When people start thinking LFTRs are some magical solution to proliferation concerns (which I've seen) that is certainly a problem.

I'll leave it to others to sift through some of the details in the comments made on the blog sited (if they wish) but a few points. The U233 used in the Teapot explosion was only in addition to Pu239 so really doesn't prove much. None of us here (at least commenting) are real weapons experts so the fact U233 has only been used so little, even in weapons testing may indicate it has more issues that even we are speculating on. Also the comment about how easy it is to either remove Pa from molten salts or especially to try to pull out any Pu produced is naive (for example, Pa233 is so intensely radioactive that ORNL never studied any removal techniques with it directly, only massively diluted with other Pa isotopes). Pulling out Pu is far more challenging from a chemistry point of view and in a LFTR any Pu you could pull out would be mostly Pu238 and useless for weapons. In Molten Salt Reactors that have U238 in the mix that make the U content worthless for weapons, trying to pull out Pu fast enough not to have large amounts of Pu240 would be hugely expensive. You could run a LWR and shut it down every month, process all its fuel and also get high grade Pu239 but it would likewise be hugely expensive and obvious to inspectors compared to far simpler methods like graphite piles (none of which are all that simple fortunately).

For at least first generation reactors I tend to prefer options referred to as DMSRs which are not directly in the LFTR category. I prefer them for cost and reduced R&D advantages but they also appear to have even greater non-proliferation features than LFTRs or LWRs.

David LeBlanc

LWRs have very low proliferation risk except for the enrichment services. It is hard to be significantly lower risk than very low risk. I think that DMSR is even lower proliferation risk than LWRs since it needs less enrichment and it generates lower quality Pu.

However, we should not limit designs to only those that are better than LWR for proliferation risk since the risk already very very low. One successful technique of those who oppose nuclear power is to always enhance requirements on all fronts and thus push up costs and then complain that the costs are just too high.

I think David Le Blanc's technical comment is largely correct. 233Pa is indeed very very hot and hard to handle. But then of course the entire reprocessing operation would be subject to intense radiation and would have to be handled remotely with all humans behind thick shielding, or a long way away. But the fact is that the removal of the 233Pa is quite an important part of the LFTR concept as it will improve the neutron economy, prevent the waste of potential fissile 233U (by making non-fissile 232U instead) and hugely reduce the radiation hazard from 208Tl (232U daughter) decay with ultra-hard 2.6MeV gamma. This is why Oak Ridge did all this work with Pa in the first place.

On the DMSR question, 233Pa removal is not part of the design, not is removal of fission products generally other than degassing of Xenon etc. But that would not prevent Pa removal being added at a later stage. And of course the DMSR which includes 239Pu and 238U in its fuel, loses an important advantage of the LFTR design, namely non-formation of long-lived Pu isotopes of atomic mass 239 or more. There is also a question of what happens to other undesirable fission products - oxygen for example, or tellurium. O will precipitate out insoluble metal oxides (including of Pa) and Tl is corrosive of the nickel-molybdenum alloy used for containment.

So the way it looks to me is, there's no free lunch here. You can have 'clean' operation of LFTR with Pa removal, but proliferation hazard, or you can have 'dirty' LFTR operation with 232U contamination and all the radiological hazard involved but reduced proliferation hazard, or you can have 'even dirtier' DMSR with long lived Pu isotopes and 232U contamination.

None of these is ideal. The picture often painted of MSR / LFTR / DMSR as problem-free nuclear technologies is not in strict accord with the inconvenient facts.

Partially true. You can design a LFTR to maximize proliferation resistance, or minimize waste production, or minimize cost, or minimize R&D. There are a variety of ways to do a good job on all but you can always put more emphasis on one feature over another.

All LFTRs will produce 232U - fast spectrum ones will produce more. Personally, I do not see production of 232U as a significant issue. It does imply fully remote handling of the fuel. But the fuel is at 600C in the first place so the requirement for remote handling is already there. The 232U is only a problem if you wish to produce uranium fuel for LWRs or weapons. Removing Pa does not decrease a reactor's production of 232U over not removing it.

Removal of 233Pa is a design feature that increases production of 233U and increases proliferation possibilities. Reactor designs that include this feature will need to have stronger safeguards than ones that do not. The losses to protactinium capture can be reduced by increasing the fissile inventory in the reactor. Increasing the fissile inventory will add to the initial cost but so does adding protactinium extraction capability. Net I believe the lower cost choice is to avoid protactinium extraction. Most of the current designs choose not to extract protactinium and accept the breeding loss due to protactinium capture. This is NOT a mandatory feature for LFTRs. As to the comment that it could be added later, yes that is true, but very hard. Adding processing to separate things from the fuel is a daunting task. One that is viewed as a significant R&D risk for expert nations. One of the reasons Pa extraction is avoided is because it is a difficult development - even for countries that have no trouble with PUREX. So if a country can develop and install Pa extraction equipment then I think they already have the technical skills to do whatever they need to do and we are not increasing the proliferation risks with this machine.

DMSR does result in some 239Pu, but not very much. If you want, you could start off by adding plutonium from spent LWR fuel in the beginning and end up net destroying more plutonium than you generate.

I don't believe the reactor generates oxygen in any measurable quantity. ORNL was concerned about how well they could keep oxygen from sneaking in - especially in their research reactor where the seals would be broken more often than in production reactors. For this reason they added 5% zirconium in the fuel salt to be the oxygen getter in the event of any air leaks. Turns out it oxygen did not leak in and the precaution of zirconium wasn't really needed.

Tellurium did pose trouble for the first Hastalloy metal they used. ORNL came up with two solutions to this. First, is to keep the chemical balance. You need to keep enough UF3 present. This isn't hard to do - they added some Be metal to the fuel salt (inserted a metallic Be rod into the fuel flow which then dissolved into the fuel) to reduce some of the UF4 to UF3. This is rather like keeping the acid/chlorine balance in a swimming pool. Don't do it and you will get a mess but it isn't hard to do. By the way, you have similar issues with LWRs - if you don't keep a proper balance in the cooling water corrosion results. ORNL also did work on slight tweaks (adding 0.5% of this and that) to the formula for Hastalloy to increase its resistance to Te attack.

It is true that some people get over-enthusiastic in their claims about LFTR. This doesn't mean that the more technical folks aren't aware that there are some tradeoffs to make. But it is also true that LFTR is a very significant advance over current nuclear power and that it is dramatically better than coal - which is still the worlds fastest growing source of electrical power. So while claims of no Pu production, no waste, and no proliferation risks aren't right - they are closer to right than claims that LFTR is more of the same or should not be pursued for any of these reasons.

Welcome to the forum, Oliver.

We need to inject a little perspective in the discussion about the proliferation of nuclear weapons. There are five "weapons-states" according to the Nuclear Non-Proliferation Treaty and everyone else is "non-weapons states". I'm not saying the treaty is or isn't a good thing, I'm just stating its parameters. The weapons states are China, the United States, Russia, France, and the UK.

Restating this list in terms of the fraction of world carbon emissions in 2008, it is China (23.5%), the United States (18.3%), Russia (5.7%), the UK (1.75%), and France (1.26%). Altogether they account for 50.5% of world CO2 emissions. Each of these countries has stockpiles of highly-enriched uranium (HEU) and weapons-grade plutonium (WGPu). They have the uranium enrichment technology to make more HEU, and they have the production reactors and chemical separations technology to make more WGPu. Each of these countries is in the process of destroying their nuclear weapons and degrading or destroying these stocks of materials. There is absolutely no reason whatsoever that a LFTR or U-233 would be used to fabricate a new nuclear weapon.

The construction or operation of any nuclear reactor in any of these countries contributes ZERO to their potential for new nuclear weapons.

The construction or operation of LFTR in any of these countries contributes zero to their potential for new nuclear weapons.

These countries are destroying fissile stockpiles, not looking for more material. The UK is expending all kinds of thought about the 114 tonnes of plutonium at Sellafield. The best thing to do would be to burn it up in a reactor. The US and Russia are downblending HEU to LEU and using it to fuel light-water reactors. The US is building at incredible expense a MOX plant in South Carolina to make MOX fuel that no utility wants to burn in their reactors, JUST to fulfill a treaty commitment about the disposition of plutonium, regardless of the cost or logic. These are not actions that countries take who have a secret thirst to build new nuclear weapons from an un-characterized material from a yet un-constructed reactor. LFTR represents exactly ZERO threat in each of these five countries.

I'm sure we can all agree that LFTR technology, with its potential to replace all electrical generation in these countries, and its potential to be used to generate synthetic hydrocarbons to displace petroleum, would be a huge asset in the struggle to reduce global carbon emissions. With widespread use of LFTR technology in each of these countries, CO2 emissions could probably be driven to ~20% of current levels by the end of the century.

This would be a great accomplishment.

Next, consider the non-weapons-states who have significant CO2 emissions. These are India (5.8%), Japan (4.0%), Germany (2.6%), Canada (1.8%), and Iran (1.8%), and South Korea (1.7%).

India already has uranium enrichment and plutonium processing technology. If there was ever a country that might pursue proliferation based on thorium, it would be India, and they haven't done it even after decades of opportunity. India's economy is developing rapidly and they appear to be set on the use of fossil fuels for economic growth.

Japan has had nuclear power plants for decades and they have developed sophisticated plutonium separation technologies as well as fast-breeder reactor technology. But they haven't developed nuclear weapons and wouldn't based on thorium, when they already have so much plutonium and the capability to get more. Japanese CO2 emissions have gone way up since they shut down their nuclear reactors after Fukushima, climbing from 374 million tons of CO2 in the year ended in March 2011 to 439 million tons of CO2 for the year, up 17 percent. This is an absolutely direct consequence of their trade of nuclear power for fossil fueled power, and is another example of the lie that nuclear reactors that are shutdown will be replaced with non-carbon sources.

Germany also has access to uranium enrichment and plutonium processing, as well as the technology for fast breeder reactors. Thorium-based technology would have no appeal to them in the development of weapons. Germany's decision to abandon nuclear will also lead to much higher CO2 emissions, as they replace nuclear power plants with lignite coal-burning power plants.

Canada specifically developed a nuclear technology (CANDU) based around use of natural uranium and heavy water, thus removing the need for uranium enrichment. Nevertheless, CANDUs produce plutonium but the Canadians have never sought to use it for nuclear weapons. A thorium-based fuel cycle would offer zero additional incentive for weapons development, when they already have hundreds of tons of plutonium in spent CANDU fuel and the ability to make more. If they wanted weapons-grade plutonium it would only take a simple modification of their fuel strategy to make it, since CANDU fuel bundles can be added and removed while the reactor is operating. But they haven't, and thus they won't. Canada's CO2 emissions will also be set to rise dramatically as they use tar sands in Alberta for energy production rather than non-carbon nuclear energy sources.

Iran is a country that probably does want nuclear weapons. But they have chosen the simplest and most effective route to getting material for those weapons, and that is uranium enrichment. Could they develop a LFTR on their own? Probably. Would they do so in order to produce material for weapons? No, not even the Iranians would do that because uranium enrichment is so much easier and proven. Iran also heavily subsidizes the internal use of petroleum products, which results in their very high CO2 emissions.

South Korea is a nation that has been very focused on the development of nuclear power for civilian applications. They have asked the US for permission to develop aqueous reprocessing of spent nuclear fuel and the US has denied that permission. (not sure why the US gets to tell them yes or no about that) Would the South Koreans develop nuclear weapons? Probably not so long as they are under the protection of the United States from North Korea, which has developed nuclear weapons using the same technique every weapons state did: namely irradiating natural uranium for a short period and chemically removing the plutonium. So would LFTRs in South Korea represent additional proliferation risk? No, not in a country that already has enriched uranium and plutonium in spent nuclear fuel.

So that's a run-down of the top ten countries in the world (accounting for nearly 70% of global CO2 emissions) and why none of them, even Iran, would use LFTR as a means of producing material for nuclear weapons. Each of these countries has the technological and economic base to develop LFTR, but if they did their goal would be energy generation, not the production of materials for weapons. Iran would be the sketchiest one, but likely even Iran wouldn't, because of their previous commitment to uranium enrichment.

Now let's talk a bit about all the other nations of the world. Would they use a LFTR to develop nuclear weapons?

No.

Because the path to developing nuclear weapons is so straightforward and has been pursued without deviation by every country that has ever tried.

1. (and by far the easiest) Enrich natural uranium to HEU.

2. Irradiate natural or depleted uranium in a reactor to make plutonium. Extract the plutonium chemically from the uranium.

That's the way it's always been done, by every country that's developed weapons.

LFTRs don't have to be perfect, just harder than the other two options. And they are harder, by far.

Of the three main fissile materials (U-235, Pu-239, and U-233) only one (U-235) occurs naturally and two (U-233 and U-235) can be isotopically diluted. U-235 arrives to us in natural form isotopically diluted.

U-232 is formed in processes related to thorium because most of the production pathways to U-232 occur only when thorium is used. The most important pathway to the production of U-232 is the presence of protactinium-231. Pa-231 has a thermal neutron absorption cross-section of 433 barns, which is nearly as large as the fissile isotopes, and is much larger than Pa-233 (38 barns) or thorium-232 (7.2 barns). So any Pa-231 in the blanket is going to gobble up neutrons and form Pa-232. Pa-232 has a half-life of only 1.3 days, decaying to uranium-232. In its short life, Pa-232 also has a large neutron absorption cross-section, and an even larger fission cross-section.



So where does Pa-231, the precursor to U-232, come from? Pa-231 is the only natural form of protactinium, formed from the decay of natural uranium-235. But there won't be much U-235 in the LFTR, and with a half-life of 800 million years, there won't be much Pa-231 forming that way.

The pathway to form Pa-231 in the LFTR that is of the most significance is the (n,2n) fast neutron reaction in thorium-232. There's lots of thorium-232 in the blanket, and provided that it is struck by a sufficiently fast neutron, sometimes it will knock off a neutron, leading the formation of Th-231 which decays quickly to Pa-231 with a half-life of 25 hours. The (n,2n) reaction in thorium-232 only has a cross-section of 0.025 barns in fast neutrons, but there's a lot of thorium-232 in the reactor.

So if one wants to maximize the production of U-232 in the reactor, one should design the LFTR to put some fast neutrons in relatively close proximity to the blanket material. That way they are not moderated (slowed-down) appreciably before they hit the blanket material. This is something that we are trying to do.

What about protactinium removal? Wouldn't it lead to really pure U-233? Not necessarily. The technique for protactinium removal that ORNL looked at involved countercurrent exchange between bismuth and blanket salt. The bismuth was loaded up with metallic thorium, and the blanket salt had small amounts of protactinium and uranium in it, along with lots of thorium. What they observed was that the extraction technique using bismuth pulled the uranium first, and then the protactinium second, out of the salt.

What kind of uranium would be in the blanket? Uranium-233 that had decayed from Pa-233 AND uranium-232 that had decayed from Pa-232. So the protactinium extraction technique removed all the isotopes of uranium and protactinium from the blanket. Thus it is very likely that if the reactor had been designed to maximize Pa-231 formation in the blanket, that U-232 would make its way into the protactinium removal system as well. Pa-231 (the precursor) would be swept out, but the very large neutron absorption cross-section of Pa-231 (larger than anything else in the blanket) would mean that it would absorb a neutron and begin its transmutation to U-232.

Pa-233 has a half-life of 27 days to decay to U-233.
Pa-232 has a half-life of only 1.3 days to decay to U-232.
Pa-231 has a very long half-life of 32,000 years, but is absorptive enough of neutrons that it would likely absorb a neutron before it was swept out by a protactinium removal system, if one was even introduced.

Maximizing Pa-231 formation in blanket salt could be an effective strategy to keeping LFTR blanket salt very unattractive to anyone with nefarious intents. Who wouldn't live in any of those top ten countries anyway, or likely any of the others as well.

Thanks a lot Kirk.

Yes! Exactly. This set of postings has so many good points in it, but this one is most important. We all need to get really good at explaining this point to people. Once again, Kirk is way in out front of the rest of us.

I calculated a few years ago that 80% of the world's CO2 production comes from nations that either are weapons states, or are adjacent to weapons states. As the electricity trade between France and Germany demonstrates, once you've got a cheap source of power, all your neighbors benefit too. A few years ago, France, through low-carbon electricity exports to Germany, was doing more about German CO2 emissions that Germany's wind and solar programs were, at vastly lower cost to German tax and ratepayers. In the last few years, the quantity numbers may have changed order, but the cost orders probably haven't.

Kirk's most recent post in this thread needs some sort of graphical explanation to make it clear.

Thanks, Kirk.

-Iain

The problem, Kirk, is that nothing is going to satisfy the anti-nukes when it comes to proliferation.

Uranium-232 is not going it impossible to use the material in a bomb. It might make it difficult. It might make it unappealing. It might make it so difficult that it would be easier to build a dedicated reactor. But it does not make it *impossible*

They will say "Okay, but if they had active cooling of the material during handling, and remote manipulators and hot cells and had heavy shielding around the weapons... couldn't they make it work as a weapon? Is that not absolutely impossible?

You will eventually have to yield to them that it is not impossible.

Don't tell me that it's totally illogical to think anyone would build a bomb like that. I know this. You don't need to convince me that it's totally unrealistic.

You're dealing with people who will never be satisfied.

What makes you think I'm trying to satisfy those people? I'm pointing out that no nation would choose LFTR technology for proliferation, not that fissile material cannot be made to detonate.

You can't prove to me that gasoline or fertilizer can't be made to explode either. You can't prove to me that someone couldn't take a kitchen knife and stab someone. Nevertheless, we continue to use gasoline and fertilizer and kitchen knives, and if we want to have economic success in the future, we will use fissile material.

Very true Kirk.

In fact, all recent wars have been fought using fossil fuel produced explosives. Some wars are even fought over fossil fuels, with fossil fuels. Without nuclear power, such fossil wars become a greater risk.

Oil is also what directly powered 9/11. Airplane powered by fossil fuel. The subsequent fossil fuel burning is also what brought down the World Trade Center, by overheating the steel to failure.

If we want to talk about proliferation, we have to mention fossil fuels. How many have died by fossil fuel produced bombs?