7 ms·

I've seen the MIT lecture that presented this. Here are the main hurdles: 1) Estimated $40 billion USD need to build a test reactor. 2) Not enough FLiBe flui

I've seen the MIT lecture that presented this. Here are the main hurdles: 1) Estimated $40 billion USD need to build a test reactor. 2) Not enough FLiBe fluid (Low-Z fluid) on the planet for the reaction chamber. Would need large scale manufacturing. Source: https://youtu.be/KkpqA8yG9T4 https://youtu.be/KkpqA8yG9T4

gameswithgo 8y ago
How hard is it to make FLiBe?
- pfdietz 8y ago
  The enriched 6Li in a single reactor would correspond to 1/4 of that produced for the entire US hydrogen bomb program. There is no facility in the world that could make the 6Li required, and the technology that was used in the US is now prohibited due to large leakag of elemental mercury into the environment (the plant used thousands of tons of liquid mercury metal.)
  - MertsA 8y ago
    As a neat coincidence, molten salt fueled fission reactors also need enriched Lithium. However, those need Lithium 7 which would essentially be the depleted Lithium from enriching Lithium 6.
    - pfdietz 8y ago
      No, MSRs do not necessarily need enriched lithium. For example, Moltex's fast MSR uses no lithium whatsoever. The (barren) coolant salt is zirconium sodium potassium fluoride, and the fuel salt (in tubes, where it does not mix with the coolant) is a mixture of sodium, zirconium, uranium, and plutonium chlorides, as well as fission products. The zirconium does not have to be "nuclear grade", since the design not only tolerates hafnium (a strong thermal neutron absorber) in the coolant salt, it depends on it to shield the reactor structure from thermal neutron degradation. Lithium-7 will still lead to production of some tritium. Any MSR using lithium is going to need a tritium separation and capture system.
      - baking 8y ago
        SPARC's models show a net positive for tritium breeding of 1.08 (tritium produced/tritium consumed) but I'm pretty sure this relies on enriched lithium, although I can't find where they specify the level of enrichment for that model. I'm sure it was a design constraint though.
      - MertsA 8y ago
        MSRs that use lithium in the fuel salt do in fact need enriched lithium. The problem is that lithium 6 has a much larger neutron absorption cross section than lithium 7. It's on the order of 10,000x greater IIRC.
        pfdietz 8y ago
        Right. It's just that MSRs don't necessarily need lithium.
        MertsA 8y ago
        Not all of them do, you're right about that.
  - 08-15 8y ago
    Why do you think it needs to be enriched?
    - philipkglass 8y ago
      The ARC paper proposes that the lithium in the salt should be enriched to 90% lithium 6 to reach a tritium breeding ratio of 1.1. See section 5.3, "Tritium breeding." https://arxiv.org/pdf/1409.3540.pdf https://arxiv.org/pdf/1409.3540.pdf I presume that the breeding ratio would fall below 1.0 with natural lithium.
      - 08-15 8y ago
        For the first proof-of-concept reactor? That's borrowing trouble. If the things works at all and the only remaining problem is the tritium supply, funding won't be a problem anymore.
        pfdietz 8y ago
        They have to breed tritium if they are to run the reactor for any significant length of time. Buying tritium externally would be very expensive -- it's $100M/kg and up, particularly if you exhaust sources like incidental production in commercial heavy water reactors. DT fusion has the nasty circular dependency that breeding blankets are needed to make tritium, but they cannot be tested without working high intensity DT fusion neutron sources.
        baking 8y ago
        To clarify, the design that the paper is addressing is the ARC, a full-size pilot reactor intended to put 200MW out on the grid for 9 working years. The demonstration reactor is the SPARC which is based on a scaled down half-sized (but 1/8 the mass and 1/8 the cost) version of ARC. While the main goal of SPARC is to achieve significant net power output, along with a proof-of-concept for many of the design features of ARC, some features may have to be left out for lack of space. So I don't know if SPARC will be able to achieve net tritium breeding, but I presume they will be testing as many of the features as they can along with taking measurements and verifying the model. It is also noteworthy that the ARC/SPARC design allows for replacement of the vacuum vessel and cooling blanket without complete removal of the outside magnetic coils, so they foresee design iteration of those components unlike the ITER design which will be pretty much locked in.
pfdietz 8y ago
World annual production of Be is just 220 tonnes. A single ARC reactor would use 40% of this. The total world Be resource is estimated at 100,000 tonnes, and if fully used in ARC reactors would supply just 1% of the world's primary energy demand.
- philipkglass 8y ago
  In mining parlance a resource is a function of economic demand as well as geology. Elements with limited demand may have "resource" levels far lower than those in regular industrial use, even if ore bodies of comparable grades actually exist for both. Uranium was produced at a level of only hundreds of tonnes per year before the development of nuclear weapons and reactors. Now it is produced in quantities of tens of thousands of tonnes per year. Obviously the terrestrial geology of uranium did not change quickly; industrial demand is what changed. Uranium's crustal abundance is comparable to that of beryllium. Despite cumulative production of more than 2.2 million tonnes uranium through 2003, additions to resource totals have kept pace with production so that overall resource levels have remained level or have increased over time. The ratio between Known Conventional Resources and reactor-related uranium requirements in 2003 was 52 compared to an average of 47 since 1985. ... Uranium production in 1945 is estimated to have totaled 507 tonnes uranium. By 1965, when the first Red Book was published, production totaled 31,564 tonnes. Production peaked in 1980 at 69,692 tonnes from 22 countries. In 2003, uranium production was reported by 19 countries with output totaling 35,492 tonnes. Cumulative worldwide uranium production between 1945 and 2003 totaled 2,204,732 tonnes... "Forty Years of Uranium Resources, Production and Demand in Perspective: The Red Book Retrospective" https://www.oecd-nea.org/ndd/pubs/2006/6096-40-years-uranium.pdf https://www.oecd-nea.org/ndd/pubs/2006/6096-40-years-uranium... It's a fair point that beryllium exploration and extraction would have to increase tremendously for routine construction of these reactors. But putting 100,000 tonnes of beryllium in ARC reactors would not mean that the Earth has then run out of beryllium.
  - pfdietz 8y ago
    However, expanding the total resource of Be by a factor of 100 would likely mean a large increase in the price of the element.
JamesCoyne 8y ago
Tossing in two cents to say the video you linked is a very good overview of the different experimental approaches to fusion. Presented by Dennis Whyte of MIT, it obviously extols the virtues of SPARC device.
Demeisen 8y ago
Another excellent talk, about a year later: https://youtu.be/L0KuAx1COEk https://youtu.be/L0KuAx1COEk
baking 8y ago
The large scale project using low temperature superconductors is ITER, initially proposed at $5 billion and currently estimated at $20 billion for a scientific test reactor. The MIT ARC design is half the size using high temperature superconductors and should be in the $1-2 billion range for a full-scale 500MW pilot production fusion reactor. What is currently being proposed (the subject of the papers being delivered tomorrow) and funded with private money is a $200-250 million SPARC (Smallest Possible ARC) that is half the size again of the full-size ARC. So yeah, you are off by a factor of 160.
- pontifier 8y ago
  I think I could build my prototype fusion device for under $1M Maybe if I said it would cost more to build, people would think it more likely to work.
  - baking 8y ago
    SPARC is trying for Q (power out/power in) in the 1-5 range. They see this as critical for getting future funding for ARC. If you think you can get net power, what are you waiting for?
    - pontifier 8y ago
      The prototype would almost certainly be break even at very low powers and densities. There are very few places where my design would lose energy, and basically gives ions unlimited chances to fuse once accelerated. I had many discussions with the head of the physics department at the local university who is a specialist in plasma physics. He was of the opinion that it would work at very low pressures/densities, but that the total output would not be high enough to be commercially viable. What is the actual benefit of a room sized $100k fusion reactor that can only put out 100 watts of energy? I believe I've solved many of those problems, but building a prototype costs $$ that I don't have to spare... I could bankrupt myself to build the prototype but I can't gamble like that with assets that currently feed my family. Though I strongly believe it will work, I'm not going to go down the same hole that Tesla went down. I have no intention of dying penniless surrounded by pigeons. I am on track to build the prototype myself without going into debt in several years once a few of my mortgages are paid off. Right now I own 100% of the IP, and have a submitted patent. I'm not actively looking for funding that would dilute me unless it's a very good deal. I'm kind of stuck bootstrapping unless I can get a grant. I have applied for several in the past, but to no effect.
justanegg 8y ago
flibe can also be used in thorium reactor and at a much smaller scale, I guess to make fusion reactors feasible you need to scale up the supply and demand of flibe. what better way to do that than create thorium reactors too.
agumonkey 8y ago
So it's mainly theoretical ?

gameswithgo 8y ago

How hard is it to make FLiBe?

pfdietz 8y ago
The enriched 6Li in a single reactor would correspond to 1/4 of that produced for the entire US hydrogen bomb program. There is no facility in the world that could make the 6Li required, and the technology that was used in the US is now prohibited due to large leakag of elemental mercury into the environment (the plant used thousands of tons of liquid mercury metal.)
- MertsA 8y ago
  As a neat coincidence, molten salt fueled fission reactors also need enriched Lithium. However, those need Lithium 7 which would essentially be the depleted Lithium from enriching Lithium 6.
  - pfdietz 8y ago
    No, MSRs do not necessarily need enriched lithium. For example, Moltex's fast MSR uses no lithium whatsoever. The (barren) coolant salt is zirconium sodium potassium fluoride, and the fuel salt (in tubes, where it does not mix with the coolant) is a mixture of sodium, zirconium, uranium, and plutonium chlorides, as well as fission products. The zirconium does not have to be "nuclear grade", since the design not only tolerates hafnium (a strong thermal neutron absorber) in the coolant salt, it depends on it to shield the reactor structure from thermal neutron degradation. Lithium-7 will still lead to production of some tritium. Any MSR using lithium is going to need a tritium separation and capture system.
    - baking 8y ago
      SPARC's models show a net positive for tritium breeding of 1.08 (tritium produced/tritium consumed) but I'm pretty sure this relies on enriched lithium, although I can't find where they specify the level of enrichment for that model. I'm sure it was a design constraint though.
    - MertsA 8y ago
      MSRs that use lithium in the fuel salt do in fact need enriched lithium. The problem is that lithium 6 has a much larger neutron absorption cross section than lithium 7. It's on the order of 10,000x greater IIRC.
      - pfdietz 8y ago
        Right. It's just that MSRs don't necessarily need lithium.
        MertsA 8y ago
        Not all of them do, you're right about that.
- 08-15 8y ago
  Why do you think it needs to be enriched?
  - philipkglass 8y ago
    The ARC paper proposes that the lithium in the salt should be enriched to 90% lithium 6 to reach a tritium breeding ratio of 1.1. See section 5.3, "Tritium breeding." https://arxiv.org/pdf/1409.3540.pdf https://arxiv.org/pdf/1409.3540.pdf I presume that the breeding ratio would fall below 1.0 with natural lithium.
    - 08-15 8y ago
      For the first proof-of-concept reactor? That's borrowing trouble. If the things works at all and the only remaining problem is the tritium supply, funding won't be a problem anymore.
      - pfdietz 8y ago
        They have to breed tritium if they are to run the reactor for any significant length of time. Buying tritium externally would be very expensive -- it's $100M/kg and up, particularly if you exhaust sources like incidental production in commercial heavy water reactors. DT fusion has the nasty circular dependency that breeding blankets are needed to make tritium, but they cannot be tested without working high intensity DT fusion neutron sources.
      - baking 8y ago
        To clarify, the design that the paper is addressing is the ARC, a full-size pilot reactor intended to put 200MW out on the grid for 9 working years. The demonstration reactor is the SPARC which is based on a scaled down half-sized (but 1/8 the mass and 1/8 the cost) version of ARC. While the main goal of SPARC is to achieve significant net power output, along with a proof-of-concept for many of the design features of ARC, some features may have to be left out for lack of space. So I don't know if SPARC will be able to achieve net tritium breeding, but I presume they will be testing as many of the features as they can along with taking measurements and verifying the model. It is also noteworthy that the ARC/SPARC design allows for replacement of the vacuum vessel and cooling blanket without complete removal of the outside magnetic coils, so they foresee design iteration of those components unlike the ITER design which will be pretty much locked in.

pfdietz 8y ago

World annual production of Be is just 220 tonnes. A single ARC reactor would use 40% of this. The total world Be resource is estimated at 100,000 tonnes, and if fully used in ARC reactors would supply just 1% of the world's primary energy demand.

philipkglass 8y ago
In mining parlance a resource is a function of economic demand as well as geology. Elements with limited demand may have "resource" levels far lower than those in regular industrial use, even if ore bodies of comparable grades actually exist for both. Uranium was produced at a level of only hundreds of tonnes per year before the development of nuclear weapons and reactors. Now it is produced in quantities of tens of thousands of tonnes per year. Obviously the terrestrial geology of uranium did not change quickly; industrial demand is what changed. Uranium's crustal abundance is comparable to that of beryllium. Despite cumulative production of more than 2.2 million tonnes uranium through 2003, additions to resource totals have kept pace with production so that overall resource levels have remained level or have increased over time. The ratio between Known Conventional Resources and reactor-related uranium requirements in 2003 was 52 compared to an average of 47 since 1985. ... Uranium production in 1945 is estimated to have totaled 507 tonnes uranium. By 1965, when the first Red Book was published, production totaled 31,564 tonnes. Production peaked in 1980 at 69,692 tonnes from 22 countries. In 2003, uranium production was reported by 19 countries with output totaling 35,492 tonnes. Cumulative worldwide uranium production between 1945 and 2003 totaled 2,204,732 tonnes... "Forty Years of Uranium Resources, Production and Demand in Perspective: The Red Book Retrospective" https://www.oecd-nea.org/ndd/pubs/2006/6096-40-years-uranium.pdf https://www.oecd-nea.org/ndd/pubs/2006/6096-40-years-uranium... It's a fair point that beryllium exploration and extraction would have to increase tremendously for routine construction of these reactors. But putting 100,000 tonnes of beryllium in ARC reactors would not mean that the Earth has then run out of beryllium.
- pfdietz 8y ago
  However, expanding the total resource of Be by a factor of 100 would likely mean a large increase in the price of the element.

JamesCoyne 8y ago

Tossing in two cents to say the video you linked is a very good overview of the different experimental approaches to fusion. Presented by Dennis Whyte of MIT, it obviously extols the virtues of SPARC device.

Demeisen 8y ago

Another excellent talk, about a year later: https://youtu.be/L0KuAx1COEk https://youtu.be/L0KuAx1COEk

baking 8y ago

The large scale project using low temperature superconductors is ITER, initially proposed at $5 billion and currently estimated at $20 billion for a scientific test reactor. The MIT ARC design is half the size using high temperature superconductors and should be in the $1-2 billion range for a full-scale 500MW pilot production fusion reactor. What is currently being proposed (the subject of the papers being delivered tomorrow) and funded with private money is a $200-250 million SPARC (Smallest Possible ARC) that is half the size again of the full-size ARC. So yeah, you are off by a factor of 160.

pontifier 8y ago
I think I could build my prototype fusion device for under $1M Maybe if I said it would cost more to build, people would think it more likely to work.
- baking 8y ago
  SPARC is trying for Q (power out/power in) in the 1-5 range. They see this as critical for getting future funding for ARC. If you think you can get net power, what are you waiting for?
  - pontifier 8y ago
    The prototype would almost certainly be break even at very low powers and densities. There are very few places where my design would lose energy, and basically gives ions unlimited chances to fuse once accelerated. I had many discussions with the head of the physics department at the local university who is a specialist in plasma physics. He was of the opinion that it would work at very low pressures/densities, but that the total output would not be high enough to be commercially viable. What is the actual benefit of a room sized $100k fusion reactor that can only put out 100 watts of energy? I believe I've solved many of those problems, but building a prototype costs $$ that I don't have to spare... I could bankrupt myself to build the prototype but I can't gamble like that with assets that currently feed my family. Though I strongly believe it will work, I'm not going to go down the same hole that Tesla went down. I have no intention of dying penniless surrounded by pigeons. I am on track to build the prototype myself without going into debt in several years once a few of my mortgages are paid off. Right now I own 100% of the IP, and have a submitted patent. I'm not actively looking for funding that would dilute me unless it's a very good deal. I'm kind of stuck bootstrapping unless I can get a grant. I have applied for several in the past, but to no effect.

justanegg 8y ago

flibe can also be used in thorium reactor and at a much smaller scale, I guess to make fusion reactors feasible you need to scale up the supply and demand of flibe. what better way to do that than create thorium reactors too.

agumonkey 8y ago

So it's mainly theoretical ?