Energy From Thorium Discussion Forum

It is currently Jun 19, 2018 7:39 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 11 posts ] 
Author Message
PostPosted: May 25, 2017 2:33 pm 
Offline

Joined: Mar 17, 2016 5:09 pm
Posts: 2
Location: American Fork, Utah
Let me begin by stating that I am a novice and this may be a silly question. It seems to me that with a dual salt LFTR that it is very important that half of the neutrons generated from fissioning uranium be consumed by other fuel-uranium and half consumed by the thorium in the blanket. Since the number of neutrons generated is just barely over two, if too many are consumed by the blanket-thorium then it seems it would lower the amount available for fissioning additional fuel-uranium while if too many are consumed by the fuel-uranium then the amount of uranium available in the fuel-salt a month later (the approximate time for thorium to breed to uranium) would be degraded. In either case it seems like there needs to be a very good balance of the generated neutrons to be consumed by the fuel and blanket in order to keep the reactor critical. How is this accomplished? Is it the placement of the blanket? Does it naturally balance somehow? Thanks for any clarification.


Top
 Profile  
 
PostPosted: May 25, 2017 3:02 pm 
Offline
User avatar

Joined: Nov 30, 2006 3:30 pm
Posts: 3624
Location: Alabama
Achieving this balance is one of the greatest challenges of a two-fluid reactor design and something I have worked on extensively for many years.


Top
 Profile  
 
PostPosted: May 25, 2017 4:37 pm 
Offline

Joined: Mar 17, 2016 5:09 pm
Posts: 2
Location: American Fork, Utah
Kirk Sorensen wrote:
Achieving this balance is one of the greatest challenges of a two-fluid reactor design and something I have worked on extensively for many years.


Thank you for replying Kirk! Is it a trade secret or other protected intellectual property to divulge if Flibe has an implementation idea from your research? I have watched all of your videos on YouTube many times. The chemistry all seems to be there but this one issue seemed to be missing for an actual implementation. I suspect there are other hurdles that I haven't the imagination to see. I would love to hear that a LFTR is being built but also understand that such information may be necessarily secret. - Dave


Top
 Profile  
 
PostPosted: May 25, 2017 9:39 pm 
Offline

Joined: May 05, 2010 1:14 am
Posts: 129
I'll quote the ' I am a complete novice ' proviso, but it seems the production of new fuel and energy would only have to balance over the longer term, not necessarily even every month or every year. Perhaps you could vary the ratio by using more neutrons for fission when electricity demand is high, and then using more for fuel when it drops to baseload. Rotating reflectors in the blanket salt maybe ? Or do you have to be super frugal with neutrons all the time just to keep power up ?


Top
 Profile  
 
PostPosted: May 26, 2017 7:31 am 
Offline
User avatar

Joined: Oct 06, 2010 9:12 pm
Posts: 138
Location: Cleveland, OH
Yes, you need to be very frugal with the neutrons all the time for a 2 fluid, thermal spectrum LFTR running the Th232-U233 fuel cycle when running a conversion ratio of 1.0 or greater.


Top
 Profile  
 
PostPosted: May 26, 2017 8:27 am 
Offline
User avatar

Joined: Nov 30, 2006 3:30 pm
Posts: 3624
Location: Alabama
Yes, discussion of core design is intentionally omitted from all my public presentations because of its proprietary nature. The reactor designs you might see in any public slide are always the ORNL-4528 (reference two-fluid) design, which is not the design of the LFTR that Flibe is developing.

ORNL-4528 is analogous, however.

I've chosen to be very open about the chemical processing because, quite frankly, without the two-fluid core design all that chemistry doesn't do you much good.


Top
 Profile  
 
PostPosted: May 31, 2017 12:39 pm 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2238
Two fluid design is, to my mind, the way to have a blanket and increase conversion.As an inexpert with limited knowledge, I feel that the blanket could be metallic thorium. It could be more easily reprocessed by electro-refining.


Top
 Profile  
 
PostPosted: Jun 05, 2017 12:29 pm 
Offline

Joined: Nov 14, 2013 7:47 pm
Posts: 568
Location: Iowa, USA
jagdish wrote:
Two fluid design is, to my mind, the way to have a blanket and increase conversion.As an inexpert with limited knowledge, I feel that the blanket could be metallic thorium. It could be more easily reprocessed by electro-refining.


That is an interesting idea, something I'll have to play with when I get the time.

Weren't there some experiments with metallic plutonium in water moderated reactors? Where the plutonium would get hot enough to melt inside the fuel rod casing? If so then it seems to me that it would be almost trivial to take the fuel rods, cut off the ends, hook it up to some plumbing, and now it's a fuel "pipe" instead of a fuel "rod". Add some fission product separation chemistry and a pump and you have a molten metal reactor.

I know, I know, it looks trivial now but I'm sure it will get complicated real quick. I know enough physics and chemistry to at least get an order of magnitude idea here. I'm sure I'll find something wrong with this real quick.

Getting back to the original question on balance of fuel and blanket salts I recall some discussion on the pro/con balance of having a large blanket salt inventory. It went something like if there is a large enough mass in the blanket salt one can avoid the need to have a decay tank to keep the Pa-233 from "stealing" valuable neutrons, this reduced complexity of the reactor comes at the cost of needing much more salt in the blanket.

The thorium, beryllium, and fluorine in the blanket might be real cheap but the reactor grade lithium is very expensive. If the cost of that lithium can be reduced then the size of the blanket can be made quite large to keep more neutrons in the reactor instead of being lost to the environment.

If using metallic thorium in the blanket then perhaps the lithium is not needed either. Maybe the blanket could still be a salt but without the expensive LiF salt to reduce costs? I'd think the coolant salt would still have to be FLiBe but perhaps avoiding the need for the expensive reactor grade lithium. I am also not an expert here but I do find this fascinating. I'll have to check my numbers later.

_________________
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.


Top
 Profile  
 
PostPosted: Jun 06, 2017 4:15 am 
Offline

Joined: May 05, 2010 1:14 am
Posts: 129
'Another early project on power reactors was the development of a fast reactor fueled by molten plutonium and cooled by molten sodium....LAMPRE I (for Los Alamos molten plutonium reactor experiment I) was operated successfully for several thousand hours following initial criticality in early 1961. One of the major research efforts was learning how to minimize corrosion of the tantalum thimbles by the molten fuel and coolant. Among the fuel elements that exhibited no leakage after thousands of hours of high-temperature (450 degrees Celsius) operation were those composed of prestabilized plutonium-iron that contained no additives and tantalum thimbles that had been annealed at 1450
degrees Celsius.'
http://permalink.lanl.gov/object/tr?wha ... UR-83-5072


Top
 Profile  
 
PostPosted: Jun 07, 2017 1:38 pm 
Offline

Joined: Nov 14, 2013 7:47 pm
Posts: 568
Location: Iowa, USA
jon wrote:
'Another early project on power reactors was the development of a fast reactor fueled by molten plutonium and cooled by molten sodium....LAMPRE I (for Los Alamos molten plutonium reactor experiment I) was operated successfully for several thousand hours following initial criticality in early 1961.
...
http://permalink.lanl.gov/object/tr?wha ... UR-83-5072


Thanks for the link, I took a quick look and that does appear to be what I was recalling, I'll read it in full later. I don't want to derail this thread to talk molten metal reactors unless others want to take it there.

Thinking a it about the question on if the fuel and blanket salts will reach a "natural balance" it does seem logical that it would. If there are "too many" neutrons in the core then it will heat and expand pushing the nuclei apart, and "leak" more neutrons into the blanket. The blanket will be exposed to these neutrons and the thorium within it will have a much higher affinity to absorb it than other elements. Assuming the blanket is of sufficient depth, mass, shape, and so on then a small enough ratio of neutrons will be lost to the environment so that the reactor will stay critical in the long run and perhaps produce some extra fissile material.

The question then becomes how to optimize this system for things like heat output, fissile material produced, costs, or whatever concerns the owners and operators of this reactor possess.

What follows then are questions of other choices one could make to optimize the system, such as using a molten metal blanket instead of a salt. Another thing that comes to mind where the experiments with aqueous reactors, where the active material was a uranium salt dissolved in water. As I recall thorium does not make a water soluble salt so that is out. Even if the material is narrowed down to being a molten salt there are a number of options on what goes into that salt, on top of the size and shape of the blanket.

Seems to me that the blanket cannot be "too big" as far as the neutrons are concerned, but it could drive up costs and make the reactor too expensive to construct and operate. Does that sound right?

_________________
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.


Top
 Profile  
 
PostPosted: Jun 10, 2017 3:03 am 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2238
jon wrote:
'Another early project on power reactors was the development of a fast reactor fueled by molten plutonium and cooled by molten sodium....LAMPRE I (for Los Alamos molten plutonium reactor experiment I) was operated successfully for several thousand hours following initial criticality in early 1961. One of the major research efforts was learning how to minimize corrosion of the tantalum thimbles by the molten fuel and coolant. Among the fuel elements that exhibited no leakage after thousands of hours of high-temperature (450 degrees Celsius) operation were those composed of prestabilized plutonium-iron that contained no additives and tantalum thimbles that had been annealed at 1450
degrees Celsius.'
http://permalink.lanl.gov/object/tr?wha ... UR-83-5072

A fire in liquid plutonium may be a bit too hot, radio-activity wise, to handle. I hope a successor would use chloride.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group