Liquid-fuel molten salt reactor?

In summary, the design is interesting, but might require a dedicated chemical reprocessing facility, which is more complexity than most electric utility companies were willing to undertake in the 1970s.
  • #1
signerror
174
3
I've run into a some advocates (assorted nuclear engineers and grad students it seems) for an unusual nuclear reactor design. It is a thermal-spectrum thorium breeder reactor. The fuel is liquid - it is a molten salt, containing the fluorides of both U-233 fuel and thorium, as well as lithium and beryllium as moderators. (As well as graphite? I'm not sure)http://thoriumenergy.blogspot.com/2006/04/brief-history-of-liquid-fluoride.htmlThe proponents claim it is a viable alternative to fast reactors, in that the fuel cycle efficiently burns all thorium fuel, and relatively little transuranic actinides are produced. They suggest fluoride salts are convenient for reprocessing based on fluoride volatility, that the closed fuel cycle would be cheaper than that of solid-fuel fast reactors (because there are fewer chemical conversions, so less reprocessing waste would be created). They claim the hot, molten fluoride salts will not corrode away the whole reactor. And they say the idea is an offshoot of a 60-year old experiment in Oak Ridge, which tested molten U-235 fluoride fuel for a reactor designed for powering nuclear bombers (airplanes).

The chief exponent is Kirk Sorensen, who is an NE grad student at UT-Knoxville.

I am not a nuclear engineer, and I have no ability to evaluate any of this. But I am intrigued by this novel-sounding idea. So, experts: is this idea interesting, or even feasible?
 
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  • #2
signerror said:
The proponents claim it is a viable alternative to fast reactors, in that the fuel cycle efficiently burns all thorium fuel, and relatively little transuranic actinides are produced. They suggest fluoride salts are convenient for reprocessing based on fluoride volatility, that the closed fuel cycle would be cheaper than that of solid-fuel fast reactors (because there are fewer chemical conversions, so less reprocessing waste would be created). They claim the hot, molten fluoride salts will not corrode away the whole reactor. And they say the idea is an offshoot of a 60-year old experiment in Oak Ridge, which tested molten U-235 fluoride fuel for a reactor designed for powering nuclear bombers (airplanes).
signerror,

I don't know about powering airplanes - but the reactor described above sounds like an experimental
reactor studied / built at Oak Ridge National Laboratory called the MSRE - Molten Salt Reactor Experiment:

http://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

[ The MSRE was housed in a building that was once used for aircraft reactor research ]

I'm dubious of the claim that the cycle would be superior to the solid-fuel fast reactor reprocessing because
of fewer chemical reactions. The Integral Fast Reactor [ IFR ] developed by Argonne National Laboratory
in the '80s-90s employed a metal fuel. Metal fuel can be reprocessed by a metallurgical technique of
electrorefining without a lot of chemical conversions. See:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

Dr. Gregory Greenman
Physicist
 
Last edited:
  • #3
Morbius said:
signerror,

I don't know about powering airplanes - but the reactor described above sounds like an experimental
reactor studied / built at Oak Ridge National Laboratory called the MSRE - Molten Salt Reactor Experiment:

http://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

[ The MSRE was housed in a building that was once used for aircraft reactor research ]

Yes, as I understand the MSRE was based on work done at the Aircraft Reactor Experiment - the wikipedia page mentions this.

I'm dubious of the claim that the cycle would be superior to the solid-fuel fast reactor reprocessing becauseof fewer chemical reactions. The Integral Fast Reactor [ IFR ] developed by Argonne National Laboratory in the '80s-90s employed a metal fuel. Metal fuel can be reprocessed by a metallurgical technique of electrorefining without a lot of chemical conversions. See:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

Dr. Gregory Greenman
Physicist

I see - so IFR is fuelled by metallic U/Pu, and so there is no oxide reduction step, as there would be for MOX fuel, or TRISO pebbles? (pardon my ignorance)

Is the fluoride reactor design sound, or is this an obvious flaw, a reason why nothing ever came out of the MSRE?
 
  • #4
signerror said:
Is the fluoride reactor design sound, or is this an obvious flaw, a reason why nothing ever came out of the MSRE?
signerror,

The molten salt reactor is a nice design. As I understand it; one of the major drawbacks is that the
reactor operator [ the electric utility company that would employ such a reactor ] would have to
operate the molten salt reactor's chemical processing facility. That is; a facility to continually
reprocess the reactor's molten fuel is an integral part of the operation of such a reactor.

Thus the operation of a molten salt reactor is more complex than even operating a commercial
light water reactor. This was more complexity than most electric utility companies at the time
wanted to undertake - they were in the business of generating power, not operating a chemical
processing plant.

The IFR concept also includes an on-site reprocessing facility - but a facility based on electrorefining
would be simpler to operate than a chemical processing plant.

For both concepts; it is a matter of how much complexity the reactor owner wants to manage.

Dr. Gregory Greenman
Physicist
 
  • #5
Here at Ohio State University, my class in nuclear design (a team based approach) investigated the LFR. It is a research based class, and each year, the class builds upon the previous year's work. It was started (I believe) here at OSU in 2004 or 2005).

The reactor does indeed use a FLiBe salt using thorium, with a blanket surrounding it as a breeder material. There were some promising results, but yes, the online processing turned out to be one of the major challenges, as well as initial startup. It required a substantial amount of U-233 to start, but eventually enough U-233 was bred so that it could supply startup uranium for additional reactors. I went through the class Fall 2007, so I don't know what advances (if any) were made this past quarter.
 

1. What is a liquid-fuel molten salt reactor (LMSR) and how does it work?

A LMSR is a type of nuclear reactor that uses liquid fuel instead of solid fuel. The fuel, typically a mixture of molten salts, is heated to high temperatures and circulated through the reactor core, where it generates heat through nuclear reactions. This heat is then transferred to a secondary coolant, which is used to produce steam and generate electricity.

2. What are the advantages of using a LMSR compared to traditional nuclear reactors?

There are several potential advantages of using a LMSR. These include a higher level of safety due to the ability to shut down the reactor quickly in case of emergency, a more efficient use of fuel, and the ability to use various types of nuclear fuel, including spent nuclear fuel from other reactors. LMSRs also produce less long-lived nuclear waste and have a lower risk of nuclear proliferation.

3. What are some potential challenges or drawbacks of using a LMSR?

One challenge of using a LMSR is the need for specialized materials that can withstand the high temperatures and corrosive nature of the molten salt fuel. Additionally, the fuel mixture must be continuously monitored and controlled to prevent potential hazards such as corrosion or nuclear reactions. There may also be concerns about the cost and feasibility of implementing this technology on a large scale.

4. Are there any current examples of LMSRs being used?

While there have been experimental LMSRs built and operated in the past, there are currently no commercial LMSRs in operation. However, there are several ongoing research and development projects, including the Molten Salt Reactor Experiment in the United States and the Molten Salt Reactor Project in China, with the goal of eventually implementing LMSRs on a larger scale.

5. What is the potential future of LMSRs and their role in nuclear energy production?

Some experts believe that LMSRs have the potential to revolutionize nuclear energy production, offering a safer, more efficient, and more sustainable alternative to traditional nuclear reactors. However, more research and development is needed to overcome technical challenges and address regulatory and societal concerns before LMSRs can be widely implemented. Some also believe that LMSRs could play a role in reducing carbon emissions and transitioning to a more sustainable energy future.

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