Energy From Thorium Discussion Forum

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PostPosted: Sep 14, 2012 1:14 pm 
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How thoroughly has this concept been explored? What kinds of liquid-fueled (not just cooled!) reactor chemistry are possible? We know flouride and chloride salts are a great option, but different configurations may have characteristics that make them favorable in one situation or another. Can you add any to the list and/or offer details about the design?


Molten Salt Reactors
Flouride Salts
Chloride Salts

Liquid Metal Fueled Reactors
Gallium-Plutonium alloy
Plutonium-iron in tantalum rods cooled by molten sodium(LAMPRE)
Uranium-Oxide in Phosphoric Acid (LAPRE I & LAPRE II) Los Alamos documentation
Bismuth-uranium
HERACLITUS - Molten Metal/Molten Salt?
LM-FR - Mg-Pu eutectic, sodium cooled

Aqueous Homogeneous Reactor

I'm not sure there is even a benefit to such an idea, but thinking of this made me wonder what a liquid-fueled, gas cooled reactor would look like.

updates:

Added documentation and the predecessors for LAMPRE. The LAPRE I & II designs were abandoned after minimal use because of pretty severe radiation leaks through the HX and into the steam system. Their reactor vessel was stainless steel with gold lining; it would be interesting to see an experiment using better structural materials like Hastelloy-N, if that's even compatible with phosphoric acid.


Last edited by Cthorm on Nov 26, 2012 5:06 pm, edited 4 times in total.

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PostPosted: Sep 14, 2012 3:20 pm 
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- LAMPRE. Los Alamos Molten Plutonium Reactor Experiment. Plutonium-iron liquid fuel in fuel rods, sodium cooled if memory serves.

- molten bismuth-uranium reactors.

- A gas cooled reactor with liquid fuel could have silicon carbide cladding with molten fuel of some sort.

There's also a big difference in internal cooling versus external cooling. Most here talk about external cooling, with molten fuel pumped through heat exchangers. The less talked about internal cooling is e.g. the LAMPRE with solid fuel, or a tub of molten fuel with heat exchange tubing in it.


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PostPosted: Sep 16, 2012 10:36 am 
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The molten metal core reactor also comes to mind: HERACLITUS, which was a concept by Argonne National Laboratory, which uses alumin(i)um or iron as solvent.


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PostPosted: Sep 17, 2012 8:43 am 
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Camiel - thanks for the suggestion. Some quick Googling based on it led me to a great ANL document(hilariously informal slides) that offers several examples of different Gen-IV categories, including liquid fueled reactors. I'll update the OP.


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PostPosted: Sep 17, 2012 2:42 pm 
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There have been extensive studies of water solutions of uranyl nitrate, including with slurries of various moderator substances.


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PostPosted: Nov 08, 2012 8:41 pm 
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I'm not a nuclear or chemical engineer but a cycle of ThF4-LiF as the blanket fuel, electrorefining for Protactinium separation, clorination of U233 and a chlorinated fuel salt burning and processing may have the best of both worlds, efficient neutron economy and an easy fision products processing. I attach a document to express my idea. Is it posible?


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Ideas for GEN IV Thorium salt Reactor II.docx [22.07 KiB]
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PostPosted: Nov 10, 2012 3:35 pm 
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Torres wrote:
I'm not a nuclear or chemical engineer but a cycle of ThF4-LiF as the blanket fuel, electrorefining for Protactinium separation, clorination of U233 and a chlorinated fuel salt burning and processing may have the best of both worlds, efficient neutron economy and an easy fision products processing. I attach a document to express my idea. Is it posible?

Welcome to the forum


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PostPosted: Nov 11, 2012 6:31 pm 
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Thank you Lindsay for the welcome.


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PostPosted: Nov 26, 2012 1:22 pm 
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I'm currently working on an aqueous homogeneous reactor that uses uranyl sulfate in light water solution as the fuel. The main goal is to design a 20 kW reactor that can be used for isotope production as well as for research capabilities for a University or other institution.

The high radiolytic gas production found in these reactors is very interesting I think. It adds an operational characteristic unique from other reactors.


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PostPosted: Nov 26, 2012 1:33 pm 
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gcarlin wrote:
I'm currently working on an aqueous homogeneous reactor that uses uranyl sulfate in light water solution as the fuel. The main goal is to design a 20 kW reactor that can be used for isotope production as well as for research capabilities for a University or other institution.

The high radiolytic gas production found in these reactors is very interesting I think. It adds an operational characteristic unique from other reactors.


Sounds like a great project George, keep us up to date. Can you give us an idea how many other groups are looking into this direction? I think the Russians have some significant work in this direction and its been awhile but I thought at least one U.S. firm was looking into this. The concept does have some huge Mo99 production advantages. It could also be a near term test bed to get regulators used to dealing with liquid fuels.

Do you have any idea what temperature is ideal? Aqueous reactors were a great idea except for the huge corrosion issues but low temperature operation of 20 kW probably removes a lot of those concerns.

David LeBlanc


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PostPosted: Nov 26, 2012 4:29 pm 
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Why is corrosion such a big deal with aqueous reactors? Just electroplate everything in multiple layers of some platinum group metal. Zero corrosion.

A much bigger problem seems to be the high pressure combined with the high vapor pressure of water at power reactor temperatures. If there's a leak, you've got fission products all over the place!

Such a reactor would best be put at the bottom of a deep pool of water. Should there be a loss of coolant, at least you can quench it with inherent pressure suppression.


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PostPosted: Nov 27, 2012 9:03 am 
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David wrote:
Sounds like a great project George, keep us up to date. Can you give us an idea how many other groups are looking into this direction? I think the Russians have some significant work in this direction and its been awhile but I thought at least one U.S. firm was looking into this. The concept does have some huge Mo99 production advantages. It could also be a near term test bed to get regulators used to dealing with liquid fuels.

Do you have any idea what temperature is ideal? Aqueous reactors were a great idea except for the huge corrosion issues but low temperature operation of 20 kW probably removes a lot of those concerns.

David LeBlanc


While at the CNS conference last June I was talking to a guy from B&W who said they have an aqueous homogeneous program in the works for a 100-200 kW reactor for medical isotope production (http://www.babcock.com/about/industries_markets/nuclear_medicine/). They are working with the radiopharmaceutical company Mallinckrodt, a subsidiary of Covidien. It seems that it will run at less than 100*C and at atmospheric but I can't tell too much from their press releases. It will definitely use LEU though.
Russia is still working with the ARGUS reactor (~20 kW), mainly working on isotope dissolution methods and converting it to LEU if they haven't already. They have been running it since 1981 so they have some good operational experience. They are probably the furthest along in bringing this technology to reality.
Los Alamos was working on isotope separation with the SHEBA II reactor, but I have not seen much literature on it since the early 2000's.

The ease of isotope separation from the fuel and the ability to put the fuel back into the reactor after the isotopes have been separated has some great advantages to solid fueled methods. No need to produce fuel assemblies and then dissolve them after their short stint in a reactor should save a lot in operational costs. It also means up to 100 times less radioactive waste to produce the same 6-day Curie value.

The corrosion issue seems to be fairly well solved if you keep the uranium concentration and temperatures sufficiently low. For a reactor with <2 kW/L power density and an average fuel solution temperature of <100*C corrosion is slow. The reactor I'm looking at will be placed at the bottom of a pool to replace the SLOWPOKE-2. It is designed to have a nominal power of 20 kW and will be run at essentially atmospheric using nothing more than natural convection to cool it. My job is to figure out if natural convection will be sufficient to keep the fuel <100*C during all possible transients.


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PostPosted: Nov 27, 2012 9:19 am 
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gcarlin wrote:
The reactor I'm looking at will be placed at the bottom of a pool to replace the SLOWPOKE-2. It is designed to have a nominal power of 20 kW and will be run at essentially atmospheric using nothing more than natural convection to cool it. My job is to figure out if natural convection will be sufficient to keep the fuel <100*C during all possible transients.


Some of us here are working on a similar issue, but with a molten salt fuelled reactor vessel in a buffer salt pool to see if we can move out the decay heat through the vessel into the buffer salt with reasonable temperatures. There are lots of ideas worth trying out such as placing a skirt all around the reactor vessel to get enhanced laminar free convection of pool coolant, but I don't have any good software for modelling this. Apparently you must have this, so if you figure out something that works well let us know.


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PostPosted: Nov 27, 2012 10:44 am 
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gcarlin wrote:
The corrosion issue seems to be fairly well solved if you keep the uranium concentration and temperatures sufficiently low. For a reactor with <2 kW/L power density and an average fuel solution temperature of <100*C corrosion is slow.


I've heard that some of the platinum group metals catalyse (recombine) hydrogen back to water. Perhaps this is a way to kill two birds with one stone? Coating all the water solution touching parts with such a metal would keep hydrogen concentrations low and prevent corrosion at the same time?


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PostPosted: Nov 30, 2012 2:10 pm 
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Cyril R wrote:
gcarlin wrote:
The corrosion issue seems to be fairly well solved if you keep the uranium concentration and temperatures sufficiently low. For a reactor with <2 kW/L power density and an average fuel solution temperature of <100*C corrosion is slow.


I've heard that some of the platinum group metals catalyse (recombine) hydrogen back to water. Perhaps this is a way to kill two birds with one stone? Coating all the water solution touching parts with such a metal would keep hydrogen concentrations low and prevent corrosion at the same time?


From my research I have seen numbers quoted in the range of 0.3-0.5 Litre/minute/kW of radiolytic gas production. To prevent an explosive concentration of hydrogen and oxygen gas forming in the head gas space above the fuel solution, a sweep gas was usually forced. The flow of this sweep gas would keep the combustible gas below the explosive limit and would carry the radiolytic gas to a catalyst chamber using something like platinized alumina pellets to recombine the H's and O's to water.

It would be interesting to figure out how much recombination could occur with surfaces coated in platinum. A forced system would likely still be required though as most of the fuel solution is not in contact with the container.

Zircaloy-2 showed strong corrosion resistance when Oak Ridge performed material testing during their water boiler program. Page 5-4 and 5-5 of the Fluid Fuel Reactors text book discuss zircaloy-2's resistance: "Titanium, zirconium, and all of their alloys were extremely resistant to attack by uranyl sulfate solutions at all concentrations, temperatures, and flow rates. In fact, corrosion damage was so small that it was difficult to detect weight changes of the specimens with a standard analytically balance."


Edit: During prompt transients radiolytic gas can form almost instantly and create a pressure burst in the solution reaching up to 100 psi if a period of less than ~10 ms are attained. It causes big swings in reactivity as the gas is instantly produced, causes a large instant negative reactivity insertion, the gas then migrates to the surface and out of the solution, the reactivity then rises back up quickly and causes another power spike. This cycle continues with smaller and smaller oscillations in power until the temperature coefficient can stabilize the overall reactivity.

This occurs with transient periods up to ~20 seconds. However the radiolytic gas has less and less of an effect on the transient as you start with a larger and larger initial period.


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