Energy From Thorium Discussion Forum

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PostPosted: Oct 09, 2016 9:49 pm 
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KitemanSA wrote:
I prefer the idea of just starting up a LFTR with a partial Pu starter charge. What I am not positive about is what percentage of the starter charge the PuF3 can be.


I think it's pretty much all or nothing. You'll either design the fuel processing system to handle a PuF3 fissile with PuF3 feed, or you'll design it to handle a UF4 fissile with UF4 feed. But not both.


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PostPosted: Oct 11, 2016 5:50 pm 
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KitemanSA wrote:
I'm not sanguine about having to reprocess PuTh MOX fuel for U233 outside the reactor complex. I'd rather have all processing with weapons grade material be integral.

It wouldn't need to be fully reprocessed before delivery. The spent MOX would likely be fluorninated at a different facility, but a MSR could be loaded with the mixed fluorides and the integral processing system used to remove fission products and residual plutonium and bring the reactor online. It may also be feasible to build a fluorination facility on the reactor site if there is a plan to build several MSRs there over an extended period of time.

There would still be the issue of separating the residual plutonium from the fission products and disposing of it, but the only better alternative for that would be a U-Pu cycle fast reactor. High burnup of reactor grade PuO2-ThO2 MOX in a water cooled reactor would result in fission of ~70% of the plutonium and conversion of most of the rest to 242Pu.


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PostPosted: Oct 11, 2016 10:05 pm 
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Kirk Sorensen wrote:
Titanium48 wrote:
It may be a while before a fissile self-sufficient molten salt reactor is ready for mass production, but ThO2 - PuO2 MOX could be used to fuel existing and near future water cooled reactors while converting plutonium into 233U. Fluorination of the spent fuel rods could then provide a startup charge for a MSR.


I am increasingly coming more and more around to this position as well.

Mr. Sorensen,
I believe that is a profound statement coming from you.

Current nuclear power reactors, even with the high profile catastrophic failures we all know about, are the safest and cleanest energy sources we know. There is no good reason that we should not be building more solid fuel water cooled reactors, even if they are little more than minor improvements over second generation nuclear reactors, because we know they provide energy that is safe, "green", and affordable.

Just getting more nuclear reactors of any kind would be a win to me. More solid fuel reactors might be a small step, and perhaps necessary step, toward getting MSRs. For those of us in the USA there is an election coming up, think about how your vote could effect the regulatory environment that nuclear power has to operate within.

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PostPosted: Oct 12, 2016 4:56 am 
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I doubt the economics will support the building of many more LWRs, which is the reason that I think it may be necessary to use the LWRs we have to produce the U233 needed to start LFTRs using a thorium/plutonium MOX fuel. But if the costs of that MOX fuel are even within an order-of-magnitude of the costs of the plutonium MOX fuel anticipated to be produced at the US MOX plant in South Carolina then the whole scheme will fall apart as nonsense. Thor Energy will have to show that they can manufacture Th/Pu MOX at a reasonable price.


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PostPosted: Oct 12, 2016 5:40 am 
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Well the MELOX Plant at Cadarache has operating costs nowhere near as high as the US MOX plant.

I would like to know what the hell is going on down there - how could it possibly cost that much?


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PostPosted: Oct 12, 2016 8:21 pm 
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Kirk Sorensen wrote:
I doubt the economics will support the building of many more LWRs...

Mr. Sorensen,
On one hand I agree with you, but only to a point, and believe that we will see heavy water reactors replace many of the current LWRs in operation now, on the other hand I believe that as these current reactors reach the end of their operational lifespan they will need to be replaced with something and putting in another LWR would seem to be the path of least resistance both economically and politically.

As you point out in your article breeding fuel in light water reactors is difficult since the light water likes to steal neutrons, I can imagine that heavy water reactors solve this problem to some extent. There is still the problem of fission products stealing those valuable neutrons that is inherent to solid fuels. Heavy water reactors seem to me to be a way to solve a number of problems with current light water reactors but not be the engineering challenge that MSRs would be. It seems to me that HWRs are likely the next step in the evolution of nuclear power that we (as a nation, species, members of this forum) have to go through to get to MSRs. I don't know if MSRs are the pinnacle of nuclear power but getting there does seem inevitable now.

I just want to emphasize my earlier point that seeing you agree with the notion of needing to breed fuel for MSRs in solid fuel reactors is surprising. I can only imagine that as something of a personal and professional admission of defeat for you. I don't mean that as a complete defeat since we (nation, species, etc.) will see MSRs at some point but just not as soon as we'd all like.

It appears to me that the viability of MSRs depends on how quickly appropriate fuel can be produced. As you point out this largely depends on the ability of someone to produce fuel rods for solid fuel reactors that contain thorium in the mix. Where you and I might disagree is in the number of future solid fuel reactors that will be built before MSRs start to replace them.

In participating in this forum the problem of obtaining enough of the right fuel to start MSRs has really set in for me recently. I get the feeling that this is something that many others on this forum have come to realize recently as well, judging by the comments I've read. I think back to the thought experiment I posed in another thread of a nation that lacked any nuclear power capability and wanted to reach energy sustainability and independence as quickly as possible. One solution that seemed to be workable was to use HWRs to breed fuel, starting with natural uranium and later a Th/Pu mix. Nations like the USA don't have the problem of a lack of enrichment facilities and such that some nation starting from nothing has but certain physical, economic, and regulatory realities mean that in a way we are starting from nothing.

The end stage, what you called the third phase, is to get LFTR, that is something that all on this forum is likely to agree on. We see the first phase in progress now, the development of solid fuel U-235 burners. Where people on and off this forum might disagree is what the second phase looks like. I'm thinking that plutonium is such an unmentionable word politically that building any reactor that intentionally creates plutonium is going to be difficult, even if the goal is to later destroy it in the same reactor. I have to wonder if there isn't another way, such as breeding thorium in a heavy water reactor using enriched uranium.

I liked your article, it spells out quite plainly on how we can get energy that is sustainable, inexpensive, plentiful, and "green". You offered a few different paths to that goal. What I see as a potential problem is any plan that includes creating more plutonium. Burning it up is "good", creating more is "bad", even if the goal is to destroy it later to produce U-233.

This gets beck to my earlier point, it is quite possible someone could produce all the U-233 needed for a future powered by LFTRs from current and near future LWRs but I have to wonder if HWRs might be a better path. Current LWRs are reaching end of life and will need to be replaced with something. That might mean another LWR, a HWR, perhaps a MSR, or even natural gas if prices stay as low as they have. From my view on the outside looking in I think HWRs are a logical next step.

As usual with most of my posts on this forum I'm mostly just thinking out loud here. I hope that I'm adding some insight to the conversation here. If someone believes I'd made some error in my thoughts here then I'd appreciate a correction.

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PostPosted: Oct 13, 2016 9:33 am 
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E Ireland wrote:
Well the MELOX Plant at Cadarache has operating costs nowhere near as high as the US MOX plant.

I would like to know what the hell is going on down there - how could it possibly cost that much?


The US DOE has a long tradition of doing pretty much everything nuclear one off without much regard to costs. Pretty much everything nuclear done by the government of the USofA is NO reference to how much something should cost.
Other governments might be far more efficient (but some are just as bad as the USA).

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PostPosted: Oct 13, 2016 9:01 pm 
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How about using molten Pu as fuel? What are the problems in getting it to selfregulate.
I figure if you use Pu to get U-233 you don't need to be careful to get as many neutrons as possible, maybe as low as getting 1 U-233 for 10 Pu would be good enough.


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PostPosted: Oct 14, 2016 1:35 am 
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Koistinen wrote:
How about using molten Pu as fuel? What are the problems in getting it to selfregulate.

Do you mean molten metal Pu as fuel or molten Pu salts? Using molten metal Pu as a fuel does sound interesting.

As I understand the problem the use of plutonium as fuel means using fast reactors. The only means we have for self regulation of fast reactors is the thermal expansion of the fuel. Also, fast reactors need a large fuel inventory to work. Getting a big pile of plutonium for use in a civilian reactor sounds problematic to me. I'm just spewing back what I recall from what I read elsewhere, someone else likely has a better answer for you.

Koistinen wrote:
I figure if you use Pu to get U-233 you don't need to be careful to get as many neutrons as possible, maybe as low as getting 1 U-233 for 10 Pu would be good enough.

One thing I learned on this forum is how expensive neutrons can be and therefore one does not throw them away without a good reason. For that to work economically the Pu fuel would have to be exceedingly inexpensive compared to the U-233 produced. I'd think that a reactor getting the performance you propose would be considered a failure and be shutdown or repurposed as a pure burner. With performance like that it would likely be cheaper to use HEU fuel to start a LFTR than the U-233 from such a process.

Where the production of such small amounts of U-233 to Pu consumed might make sense is if people simply want to destroy their stockpile of Pu and for some reason are not concerned about having enough fissile fuel in the end to sustain a fission economy. That's for people that want to SHRINK their nuclear power capacity, not GROW it. That is unless these reactors produce more Pu along with the little U-233 produced. That would mean a very long "Phase 2" of plutonium breeding before these people got to the "Phase 3" of a sustainable Th/U-233 economy, or these people are happy with staying in "Phase 2" of a Pu breeding economy and the production of the U-233 is just a means to stretch out their supply of mined uranium with thorium.

That is an interesting view to take, Koistinen. You gave me something to ponder.

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PostPosted: Oct 14, 2016 8:11 am 
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There was at least one reactor experiment (LAMPRE) run with a molten plutonium-iron eutectic.


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PostPosted: Oct 14, 2016 8:23 am 
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The idea behind using the plutonium in a LFTR would be the two-fold objective of destroying/fissioning the Pu while producing U233 in the thermal spectrum range. This would essentially be using the LFTR as a burner, not a breeder or iso-breeder since the CR of Pu would be under 0.65 in the thermal spectrum.

So, a place like ORNL could have multiple LFTRs burning the Pu to dispose of it, generate electricity for itself or TVA, while creating the U233 that could be used in other LFTRs by power companies like Southern. I know some will be unhappy about the efficiencies of the neutron usage, but it is superior to use in U/Pu MOX fuel in a PWR or BWR. The idea of using Pu/Th fuel in a LWR is interesting, especially if the fuel elements were annular shaped and/or metal. A metallic annular-shaped fuel element would keep the centerline Tmax low, transfer heat to water better, handle FPs, gases better, reduce swelling, achieve greater/longer burn-up, and eventually would have U233 recoverable from the fuel.

I think the politics of disposing Pu may favor using a MSR, such as LFTR, since it looks far cheaper and faster than the SRS fiasco. The politicians and regulators will not care about neutron efficiency, so LFTR will look better than using chloride salts since it is further developed. Liquid metal fast reactors have their own issues and history and are less likely to be chosen. A savvy politician could sell the idea of LFTR and make thorium a buzzword - bright, shiny, and new vs. how demonize Pu and U have become. Maybe.

Jim L.


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PostPosted: Oct 14, 2016 9:01 am 
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Jim L gets the picture. The fact that plutonium burns poorly in the thermal spectrum is not really that big of a deal when you're mainly trying to get rid of it. Exactly what the amount of U-233 that could be produced per unit of plutonium destroyed is not known, but the argument for going forward with the idea is pretty forgiving even if the number is bad.

After spending decades trying to make plutonium now we're trying to get rid of it. Consuming it in the presence of thorium is the ONLY way to do so without making more plutonium. That's another reason why uranium-plutonium MOX is such a dead end.


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PostPosted: Oct 14, 2016 5:46 pm 
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Kurt Sellner wrote:
Do you mean molten metal Pu as fuel or molten Pu salts? Using molten metal Pu as a fuel does sound interesting.

I mean molten metal Pu. Perhaps at high enough temperature to get rid of many fission products by boiling them off.


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PostPosted: Oct 14, 2016 7:04 pm 
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Jim L. wrote:
I think the politics of disposing Pu may favor using a MSR, such as LFTR, since it looks far cheaper and faster than the SRS fiasco.

Which SRS fiasco are you referring to? There were so many.

It appears to me that Phase 2 of this three phase plan has many options. I can see the second phase taking the form of Pu burning and U-233 breeding MSRs but I believe that with the politics of nuclear power as they are now a more likely path is solid fuel water cooled reactors to produce the U-233 needed for Phase 3.

What is perhaps even more likely is Phase 2 taking multiple but not quite parallel paths. Phase 2A would be using solid fuel reactors with a Th/Pu mix fuel, using currently operating reactors and/or ones built in the next decade or two. Phase 2B would include MSRs fueled with Pu to breed U-233. For Phase 2 to happen we'd need a political and economic environment where the players agree that Phase 3 exists and includes LFTR. I can imagine a lot of people would be quite pleased staying in Phase 2 with a plutonium breeder economy. This may work towards Phase 3 by creating an abundance of inexpensive plutonium fuel but could also work against it by creating a new economy where Phase 3 is seen as a way to obsolete them. Thorium energy advocates may inadvertently be creating their own competition.

We may find ourselves in a position where some of the players don't see the value in LFTR. In this case it may be beneficial to offer an alternate view of Phase 3, or rather an option of Phase 3A being solid fuel thorium reactors and Phase 3B being LFTR. It's been said many times by many people in nuclear energy that the existing nuclear power reactor manufacturers carry a lot of weight in making policy. LFTR is a threat to their business model or at least can be interpreted as such.

We may find ourselves in a situation where Phase 2 is exceedingly successful in producing U-233 but there are no LFTRs to burn it yet. This would be where Phase 3A comes in with solid fuel reactors burning the U-233, with either Th or U-238 in the fuel to breed more fuel for the future. There is also the possibility of a Phase 2C and 2D, or skipping Phase 2 completely and starting LFTRs with HEU which leaves us in a place where we might just bury all the Pu we've made in the last 70 years and pretend it doesn't exist.

I like how Terrestrial Energy has placed their products in a way that they are viewing fossil fuels not as a competitor but as a customer. I think a path of least resistance for a thorium fueled future would include existing nuclear power reactors, and the industry around them, as customers instead of competitors. Perhaps this would take the form of making a deal with the existing nuclear power industry to make the Pu for fueling MSRs and the MSRs producing U-233 for them to burn. Perhaps some other arrangement can be made.

My point is that if we want to see thorium as a fuel, and LFTR part of that future, then we are going to have to provide the existing nuclear power industry a way to be a part of it or they will fight back. There is a lot of money in making fuel rods, and if the people making these fuel rods can be convinced that thorium is a good fuel then they will use a part of that money for things like influencing policy on thorium mining and spent nuclear fuel reprocessing.

I don't believe I'm saying anything that everyone here does not already know. My hope is to frame the problem in a way that solutions can be found.

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PostPosted: Oct 14, 2016 7:32 pm 
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Koistinen wrote:
Kurt Sellner wrote:
Do you mean molten metal Pu as fuel or molten Pu salts? Using molten metal Pu as a fuel does sound interesting.

I mean molten metal Pu. Perhaps at high enough temperature to get rid of many fission products by boiling them off.

My first reaction to reading that was to cringe at the thought of boiling off cesium. I don't know how exactly cesium in molten plutonium would act but if the idea is to boil off metallic fission products then I'm left thinking that this is a bad idea.

After thinking it through further the molten plutonium is likely to be an alloy with a melting temperature not that different from many molten salt designs. What the melting temperature would be exactly depends on the design choices one makes and the alloy chosen to meet them. If this molten metal reactor is to be a fast reactor then it still has the control issues inherent with all fast reactors. If the intention is to make a molten metal thermal reactor then there is the inherent problem of plutonium capturing thermal neutrons instead of fissioning.

If the goal is to simply find a way to destroy the plutonium, with little or no concern of it's ability to produce energy or fuel, then a molten metal reactor may be a good idea. This avoids the cost of fabricating fuel rods and, as you point out, some fission products will boil out making it easier to dispose of them or use them for medical or industrial products.

If the goal is to use a molten metal reactor to turn Pu into U-233 then I'm simply left pondering if or how it would work. The molten metal core would quickly become quite the mulligan stew of various metals in various isotopes. I can only imagine that molten salts must be an easier reactor to build or there would be more people advocating for it instead. It's also quite possible that not enough people thought it through even though it might avoid many of the engineering challenges to MSRs.

Again, this is something to ponder.

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