Energy From Thorium Discussion Forum

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PostPosted: Sep 07, 2010 10:24 pm 
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bwebb wrote:
Pretty good approximations, Gentlemen.

There are a few things we have to keep as a trade secret, however.

I have two questions what would a Thorium Core look like. Triangular pitch?, p/d ratio, first core mixture of UO2 and ThO2.

Also if anyone is interested see our website for careers.

Thanks... Brent


Welcome Brent,

You'll have to excuse some healthy suspicion and speculation since exaggeration of abilities is often rampant in start up high tech companies. In general I really like the Nuscale design and approach but some things just look almost too good to be true at times. Can you at least comment on the rough estimate of 1 psi driving force? Do you happen to know what the driving force in the SBWR design that looked to also use natural circulation (but with the advantage of a phase change and much bigger density change for thermosyphoning).

I'm not sure I understand your question. Are you asking for speculation about what a Nuscale core might look like if trying to use thorium? Or are you just curious about thorium use in PWRs in general? Most on this site are working or at least interested in molten salt reactors using thorium so not too much expertise likely on ThO2+UO2 use. Obviously the Radkowski efforts and Thorium Power (now Lightbridge) would have the experts on that. Many of us here consider thorium use in LWRs to be of minimal benefit though.

David LeBlanc


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PostPosted: Sep 11, 2010 9:37 pm 
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What is the great mystery here? Just go to their website and most of your questions will be answered. There are 24 standard 17x17 fuel assemblies that are 6 feet tall instead of the typical 12 feet. Pressure available is simply a matter of height times density difference. I suspect that they have optimized for least cost with a larger temperature difference than typical PWR's. Note the lower operating pressure and lower efficiency than modern PWR's. Using the $1,000,000 per fuel assembly rule of thumb for new fuel assemblies, the initial fuel load will cost about $12,000,000 since these are just half the height. This is just over $250/KW, only about 6% of the initial cost.

Assuming a typical 3 batch loading system, they will probably achieve 60 MWd/kg burn-up and their fuel cost will be well under $10/MWh. This tiny extra fuel cost compared to large scale LWR’s because of lower efficiency and slightly lower uranium utilization because of larger losses from a smaller core is a very small consideration compared to the active safety systems that a smaller reactor eliminates.

This is far closer to an operating reactor than LFTR. There is an electrically heated 1/3 scale prototype that is being used to determine actual flow characteristics. The data they have gathered is very valuable and they certainly are not going to give away their results. They are not going to tell everyone any unexpected results and I suspect that even the licensing documents will be kept as confidential as possible as long as possible.

I understand that this is a Thorium site, but I think most here would agree that clean, safe, economical power is a good thing. When I discovered that uranium, without enrichment and fabrication, is only about $.30 per MMBTU equivalent, I lost most of my interest in Thorium. And now they are practically giving away surplus weapons grade fissionable material. If Thorium were free, it would reduce the cost of nuclear electricity by only a few percent, assuming that no additional costs would be required to accommodate a Thorium fuel cycle.

Unless the safety systems and licensing costs can be reduced, nuclear is not competitive with coal. This is strategy of NuScale and they have been very deliberate about making sure the licensing process is ready. By contrast, a LFTR reactor has all sorts of issues that may literally require an Act of Congress to resolve. People rationally fear the new and unknown and the regulator’s job is to protect people regardless of cost.

If molten salt fuel really solved more problems than it causes, someone in the world would have developed it by now. Flourinating a hot witch’s brew of uranium, thorium, and dozens of fission products sounds like a nightmare to me. How can we reasonably expect a regulator to approve of that?

The nuclear industry needs to support NuScale and we need to get ahead of public fears. Reasonable licensing is essential for the next generation of nuclear plants.


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PostPosted: Sep 11, 2010 9:51 pm 
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Moliterno wrote:
If molten salt fuel really solved more problems than it causes, someone in the world would have developed it by now. Flourinating a hot witch’s brew of uranium, thorium, and dozens of fission products sounds like a nightmare to me. How can we reasonably expect a regulator to approve of that?

The nuclear industry needs to support NuScale and we need to get ahead of public fears. Reasonable licensing is essential for the next generation of nuclear plants.


There is no need to fear the chemistry...

The MSRE was killed off 40 years ago for what amounts to political reasoning that no longer applies...

The beneifts are more clear now than ever...


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PostPosted: Sep 12, 2010 2:14 am 
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Well chemically there are significant quantities of highly reactive materials in the fluorinator/defluorinator equipment. Free fluorine, hydrogen, and hydrogen fluoride. There are also beds of NaF and MgF2 contaminated with fission products that have to be stored, and cold traps that can fail and concentrate 100% pure UF6 leading to possible criticality issues. There is also the proliferation issue; the UF6 is so pure and not very warm, you can handle it with gloves. Bottom line is that a lot of engineering is required to make the components safe.

If we just use a vacuum still (possibly slightly higher temperature) then we don't do anything chemical to the fuel. The chemists won't be happy, as they want to make messes first and then clean that up by adding other messes. Very strange bunch, them. :mrgreen:

With a once through DMSR no online fuel reprocessing is required at all.


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PostPosted: Sep 12, 2010 9:16 am 
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Cyril R wrote:
If we just use a vacuum still (possibly slightly higher temperature) then we don't do anything chemical to the fuel. The chemists won't be happy, as they want to make messes first and then clean that up by adding other messes. Very strange bunch, them. :mrgreen:


Purely physical separation techniques with no chemical feedstock and the associated contaminated leftovers are, indeed, very appealing. Unfortunately, a still will not produce anywhere near the same separation as fluorination.

Alvin Weinberg writes with wonder about holding a small container of uranium that was separated from gigacuries of fission products in the MSRE core in the process of switching it to a different fuel. Nothing but fluorination can achieve such separation ratios that can make it safe to handle.

Do we really need such perfect separation? That's a good question.


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PostPosted: Sep 12, 2010 10:14 am 
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I feel that electrolysis would be a good way to separate elements. It is a standard industrial refining process.


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PostPosted: Sep 12, 2010 10:38 am 
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Owen T wrote:
Cyril R wrote:
If we just use a vacuum still (possibly slightly higher temperature) then we don't do anything chemical to the fuel. The chemists won't be happy, as they want to make messes first and then clean that up by adding other messes. Very strange bunch, them. :mrgreen:


Purely physical separation techniques with no chemical feedstock and the associated contaminated leftovers are, indeed, very appealing. Unfortunately, a still will not produce anywhere near the same separation as fluorination.

Alvin Weinberg writes with wonder about holding a small container of uranium that was separated from gigacuries of fission products in the MSRE core in the process of switching it to a different fuel. Nothing but fluorination can achieve such separation ratios that can make it safe to handle.

Do we really need such perfect separation? That's a good question.


Not for normal operations but for the final separation before sending things to waste.
So for the reactors we don't really need fluorination but for the central processing station we need not only fluorination but something fancier as well to grab the plutonium etc.


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PostPosted: Sep 12, 2010 10:42 am 
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Owen T wrote:
Cyril R wrote:
If we just use a vacuum still (possibly slightly higher temperature) then we don't do anything chemical to the fuel. The chemists won't be happy, as they want to make messes first and then clean that up by adding other messes. Very strange bunch, them. :mrgreen:


Purely physical separation techniques with no chemical feedstock and the associated contaminated leftovers are, indeed, very appealing. Unfortunately, a still will not produce anywhere near the same separation as fluorination.

Alvin Weinberg writes with wonder about holding a small container of uranium that was separated from gigacuries of fission products in the MSRE core in the process of switching it to a different fuel. Nothing but fluorination can achieve such separation ratios that can make it safe to handle.

Do we really need such perfect separation? That's a good question.


You cannot have cake and eat it. Easily accessible UF6 will please the proliferation antis for sure. This wasn't really on the agenda in Weinberg's time. My current thinking is to operate the still slightly higher in temperature to get reasonable U losses. What Lars says is also true. "no chemical fuel reprocessing" is also good PR for us. The chemists have made expensive messes with their aqueous fuel reprocessing, and the word itself has become quite contaminated. That's just my opinion.


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PostPosted: Sep 12, 2010 10:45 am 
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jagdish wrote:
I feel that electrolysis would be a good way to separate elements. It is a standard industrial refining process.


Its better than the aqueous techniques though still leaves some contaminated cathode/anode wastes. Probably not something that will be used at scale for an online reprocessing unit, but perhaps its a good way to grab some fissile out of spent solid fuels to start some MSRs.


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PostPosted: Sep 12, 2010 1:39 pm 
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Cyril R wrote:

...
You cannot have cake and eat it. Easily accessible UF6 will please the proliferation antis for sure. This wasn't really on the agenda in Weinberg's time. My current thinking is to operate the still slightly higher in temperature to get reasonable U losses. What Lars says is also true. "no chemical fuel reprocessing" is also good PR for us. The chemists have made expensive messes with their aqueous fuel reprocessing, and the word itself has become quite contaminated. That's just my opinion.


Yes, that's exactly my point. Purely physical separation is preferred - if it's good enough. Is distillation up to the task?

How about this: after distilling a salt with high UF4 content bring it close to its solidus and lower a chunk of pure crystallized UF4 into the pot and slowly lift it. I believe it should grow into a crystal of high purity. It can be further processed by zone refining. Would this work?


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PostPosted: Sep 12, 2010 1:56 pm 
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Owen T wrote:
Cyril R wrote:

...
You cannot have cake and eat it. Easily accessible UF6 will please the proliferation antis for sure. This wasn't really on the agenda in Weinberg's time. My current thinking is to operate the still slightly higher in temperature to get reasonable U losses. What Lars says is also true. "no chemical fuel reprocessing" is also good PR for us. The chemists have made expensive messes with their aqueous fuel reprocessing, and the word itself has become quite contaminated. That's just my opinion.


Yes, that's exactly my point. Purely physical separation is preferred - if it's good enough. Is distillation up to the task?

How about this: after distilling a salt with high UF4 content bring it close to its solidus and lower a chunk of pure crystallized UF4 into the pot and slowly lift it. I believe it should grow into a crystal of high purity. It can be further processed by zone refining. Would this work?


I guess we can afford to throw out 1% U233 per year or so since we just need isobreeding. If we process 5 times a year we need to get 99.8 percent efficiency with the still, which seems possible (UF4 is much more volatile than LiF). The ORNL documents don't appear to have figures on still efficiency? Maybe that makes sense since they already had fluorination. Which makes sense since they focused on the maximum breeding ratio possible...

The U233 isn't wasted. One might attempt to fluorinate it in a guarded, centralized facility (or bring the guarded facility and personell to the reactor at the end of reactor life). Or use an expensive very high temperature very high efficiency still. That way we can get away with a simple cheap reliable little still for the online processing.

Isn't crystal growing a very slow process? Wouldn't you need a huge bath with numerous crystal seeds?


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PostPosted: Sep 12, 2010 3:19 pm 
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Cyril R wrote:
...
Isn't crystal growing a very slow process? Wouldn't you need a huge bath with numerous crystal seeds?


Yes, it's pretty slow. But the rate of U production is quite slow, too. It seems like a pretty straightforward process (after you finish tearing your hairs out debugging it) consisting of simple mechanical manipulation. Assuming it can be made to work I think it should be an attractive option. I believe the initial concentration of the material should be relatively high for this to work well so it should be used on a distillation fraction rather than the whole liquid.

It could work for other materials too like recovering thorium in a single fluid reactor.


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PostPosted: Sep 12, 2010 3:31 pm 
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Owen T wrote:
Cyril R wrote:
...
Isn't crystal growing a very slow process? Wouldn't you need a huge bath with numerous crystal seeds?


Yes, it's pretty slow. But the rate of U production is quite slow, too. It seems like a pretty straightforward process (after you finish tearing your hairs out debugging it) consisting of simple mechanical manipulation. Assuming it can be made to work I think it should be an attractive option. I believe the initial concentration of the material should be relatively high for this to work well so it should be used on a distillation fraction rather than the whole liquid.

It could work for other materials too like recovering thorium in a single fluid reactor.


Oh, so that would be for the still bottoms, ok. Something funny will probably happen to the different salt compositions when you chill it. For example, cooling FLiBeU just above freezing point gets you a 89 at% LiF-BeF2 phase, and a seperate 11 at% LiF-UF4 phase. Maybe we can use this to our advantage, as pre-reprocessing, getting the volumous LiF-BeF2 phase out with a centrifuge or something. I bet if there are a lot of different fission product fluorides things will get very complicated, though. But any reprocessing scheme that doesn't involve any chemistry change I find very interesting.


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PostPosted: Sep 12, 2010 6:50 pm 
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I have performed the pressure drop calculations and they are indeed less than 1 psi as presented in our public presentation. As reported in the natural circulation literature, the primary flow rate is dependent on the elevational head between the centers of the reactor core and the steam generator. Further, much time and analysis has been spent on mitigating form and friction pressure losses within the system and its components. NuScale has several patent applications in process, so I can not elaborate at this time.

NuScale has several engineering positions currently open for thermal mechanical engineers.

I am interested in thorium fuel and how it maybe used in our reactor system. I would like to discuss its potential benefits.


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PostPosted: Sep 12, 2010 9:22 pm 
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bwebb wrote:
I have performed the pressure drop calculations and they are indeed less than 1 psi as presented in our public presentation. As reported in the natural circulation literature, the primary flow rate is dependent on the elevational head between the centers of the reactor core and the steam generator. Further, much time and analysis has been spent on mitigating form and friction pressure losses within the system and its components. NuScale has several patent applications in process, so I can not elaborate at this time.

NuScale has several engineering positions currently open for thermal mechanical engineers.

I am interested in thorium fuel and how it maybe used in our reactor system. I would like to discuss its potential benefits.


There have been numerous studies on the use of Thorium in LWRs and they should be applicable to your reactor, including the concept that Lightbridge has been offering. The use of thorium can provide some reduction in uranium usage and perhaps better waste characteristics, however, the benefit is limited without recycling. The best performance (in terms of the highest conversion ratio) is obtained with a tight lattice, such as shipping port used. This will result in a larger core pressure drop and therefore would probably not be possible in your system.


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