Nuclear Fusion Power and Science

I have a farely comprehensive understanding of the huge challenges needed to create commercial nuclear fusion power. This is why I am more optimistic about molten salt nuclear fission. I try to explain this in two videos. However, this is a complex topic. I will try to state this as clearly and briefly as possible here.

How Far Away in Commercial Nuclear Fusion?

I believe technological breakthroughs are still needed. The recent decades of work to nuclear fusion has been dominated by the Tokomak projects (ITER, JET and a south korean Tokomak and a Chinese Tokomak). Tokomak hold nuclear fusion plasma in a donut shape magnetic field. It takes years for the projects to build up to attempts to create fusion for a few seconds and the fusion is roughly 1000X times away from real net energy.

There are many ways of trying to develop nuclear fusion to generate power. A single value starts to tell us how close a fusion experiment is to net power: the fusion triple product. The triple product is the product of three attributes of a fusion plasma:

n the density of ions in the plasma (ions/cubic meter)
T the temperature of those ions (keV2)
τE the energy confinement time (seconds)

The fusion reaction with the lowest (aka most achievable) triple product threshold is the fusion of deuterium and tritium (D-T), two isotopes of hydrogen. A fusion power plant running on D-T fuel will have a triple product of about 5×10^21 m-3 keV s or greater. There are many other requirements for a commercially viable power plant but the triple product is a minimum technical milestone.

A nice property of the triple product is that it’s independent of the particular scheme used to create the fusion plasma so it can be used to compare performance across different kinds of approaches to fusion. It’s a meaningful quantity in magnetic confinement schemes (tokamaks, stellarators), inertial confinement schemes (laser fusion), and magneto-inertial schemes (MagLIF, compression of FRCs).

Steven Krivit at NewEnergy Times has published a 26 page pdf and many other articles that describe misrepresentations by the multi-billion Tokomak project ITER.

The multi-billion JET (Joint European Torus) reactor experiment has operated for decades. I think it was at about 100 million euros per year or more for its funding. In March 2019, the UK Government and European Commission signed a contract extension for JET. This guaranteed JET operations until the end of 2024 regardless of Brexit situation. In December 2020, a JET upgrade commenced using tritium, as part of its contribution to ITER. On 21 December 2021, JET produced 59 megajoules using deuterium-tritium fuel while sustaining fusion during a five second pulse, beating its previous record of 21.7 megajoules with Q = 0.33, set in 1997. Steven Krivit points out that JET consumed power at a rate of 700 MW for 5 seconds, it took 3,500 MJ to produce the 59 MJ. The Q = 0.33 is 33% of the energy in and out of the plasma. The wall power is about 60 times less and then the power out of the plasma would need to be converted back to electricity. This goes to the more honest figures from LPP fusion. Fusion power experiments are at one thousandsth of a percent in total electricity out versus electricity in.

The world only has 25 tons of Tritium. It does not occur naturally. A D-T (deuterium and tritium) fusion reactor generating a gigawatt would need about 150 tons of Tritium per year. Tritium is currently produced at heavy water CANDU (Canadian) made nuclear fission reactors.

The D-T fusion reactor plans need to address breeding a lot of Tritium. This means generating a lot of cheap neutrons to efficiently convert lithium into Tritium. This is like saying we would have a nuclear fission plan to make abundant amounts of Plutonium. Plutonium does not occur in nature but you can make it by reacting Uranium 238 with neutrons. Uranium 238 is 94% of what people call nuclear waste. Uranium 238 is about 99.3% of naturally occuring Uranium and 97% of current fresh nuclear fuel rods.

A country that can generate a lot of cheap neutrons to breed a lot of Tritium would mean that country could also breed a lot of Plutonium. Any country that can breed a lot of Plutonium can make a lot of nuclear fission bombs.

I am actually relatively OK with this because I think nuclear fission bombs will become outdated. The world will progress to a lot better technology in space and energy then the destructiveness of fission bombs will be not be military strategic and will become less important militarily. This is not to say proliferation should be encouraged. Steps should be taken to not be stupid, but a world with mastery of nuclear for energy and space propulsion will mean a world where nuclear weapons are relatively trivial. They will become like molotov cocktails.

Successfully developing nuclear fusion for energy has to go beyond all of this small level of current power generated relative to the power used and do it economically. The Tokomak projects have to implicitly generate this net positive power while holding plasma for years instead of seconds. I like nuclear fusion projects that plan to not hold plasma. Those projects use pulsed power. They briefly (tiny fractions of second) create fusion conditions and try to get massive amounts of power and get the power out without using a turbine. Using a turbine means sustaining fusion like nuclear fission plants now which operate like coal plants. Turbines work with a large amount of sustained heat. Think massive contained coal fires.

LPP Fusion is a small company that is trying to get to advanced nuclear fusion that has only had a few million dollars in funding. However, percentage of power in to percentage of power out they are very close to the big JET (Joint European Torus). LPP Fusion, Helion Energy, HB11 Fusion, TAE are trying to go for forms of pulsed fusion. See the top image in this article. LPP Fusion plan highlights are below.

I also prefer projects going for advanced fusion reactions. 1 Billion degrees instead of 100 million degrees.

Here is my nuclear fusion project tracking spreadsheet image.

Here is some slides from LPP Fusion.

18 thoughts on “Nuclear Fusion Power and Science”

  1. It’s true that nuclear weapons already are outmoded practically. They’ve never been a strategic weapon for obvious reasons…everyone loses so no one realistically would even consider it as a warfighting solution. But with conventional lobbing of hypersonic missiles/projectiles you can get much bigger bang for the buck without the fallout poisoning your own land.

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  2. One more, if I may.

    I am an old no-nuker. But molten salt fission reactors appear to be very safe, and fast-neutron MSRs can, we’re told, burn up the 96 percent of fissionables–mostly U-238, but anything that can fission–that we currently call waste; burn it to produce power instead of leaving it for the great-grandkids to try to store safely for millions of years. That cleans up our mess, and we should have plenty of fuel already on hand to last until fusion can completely replace fission.

    Small MSRs are being developed to power commercial shipping, too, cleaning up another nasty source of atmospheric carbon. I can’t wait.

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  3. The numbers on tritium are wrong. There are 20-25 kilograms available, not tonnes. A gigawatt reactor would require only 150 kg per year. The majority (or all of it) can hopefully be generated by the reactor (lithium coating).

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    • Yes, it is 25 kilograms not tons available. The breeding with a lithium blanket has not been tested but research suggests only 10-20% breeding ratio for the MIT reactor. General Fusion talks about 50% extra breeding ratio.

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      • I don’t think this is correct.
        See this paper: https://dataverse.harvard.edu/file.xhtml?fileId=4864575&version=1.0

        The TBR you have cited appears to be for unenriched lithium. With lithium-6 enrichment to 20-50% they get a breeding ratio of well above 1 in their study.

        It is also not necessary to get the breeding ratio above 1 in some designs.

        There is always some D-D fusion occurring at something like 1-10% of the rate D-T fusion rate is occurring (depends on ion temperature). D-D fusion makes a triton 50%, which will then fuse and make another neutron and 50% of the time it makes a neutron + a He-3 50% of the time, and that extra neutron can go on to breed another triton at similar tritium breeding ratio as a D-T fusion neutron. If you can make the reactor a little bit better and crank the D-D fusion fraction up a little bit the TBR is reduced. As we get more experience building these things in the more distant future the TBR can be gradually reduced, lithium enrichment removed, etc.

        There are also ways to boost the TBR without improved geometry. Enriching the lithium, even just a little bit, with lithium-6 makes a big difference. Adding beryllium generates extra neutrons. Adding fissionables and fissiles can do this too. If you have a flowing curtain of FLiBe-salt as the first wall you can maybe add TRUs and call it a nuclear waste burner; high Z atoms are not desirable in the plasma, so these would have to be cleared between shots. D-T neutrons are very high energy and can split many even numbered higher actinides that cannot sustain a chain reaction and generate a net positive number of neutrons. This makes a lot of fission products and requires some kind of reprocessing of the blanket salt to remove them and vitrify the ones that aren’t useful. The salt would then be pumped around through a heat exchanger to a clean/non-radioactive salt that goes out and drives a steam engine or similar.

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  4. Fusion Q values change very rapidly in certain circumstances so that wall plug or Q total can leave you out of the loop on capabilities

    Compare JET’s Q of .33 to ARC’s proposed Q of 13. This makes sense if you know the difference between their magnet’s capabilities. If you compare their Q total you’re going from .01 to 3 and you didn’t see it coming

    The best Q reporting would be the Q plasma and the Q needed for commercialization. Generally they say steady state plasmas need a Q of 20 and laser pulsed needs 100. Interestingly I think Helion’s looking for 8, though needing D-D levels of triple product

    For proton-boron let’s say the engineering is twice as easy, I think you’d need a triple product 50x higher than a similar D-T project as the p-B11 needs a billion degrees. This is perhaps a wild guess but could be basically reasonable. In my view pulsed alternatives are the best near to medium term bet due to engineering advantages while tokamaks need some kind of additional advance past HTS magnets to be commercially mainstream

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    • D-T needs a higher Q value because it relies on converting neutron kinetic energy to boiling water to spin a turbine. We’re talking ~33% efficiency of heat conversion to electricity.

      Other fusion approaches could succeed with lower Q values because they produce electricity more efficiently than boiling water. Direct conversion to electricity from charged particles or magnetic fields.

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      • Indeed, that’s why LPP is relying on extremely efficient direct conversion, and that X-ray photo-voltaic setup. P-B fusion is so marginal in terms of energy return relative to energy invested that they can’t afford to leave any energy on the table at all. Not just because of low energy out, but high losses, too.

        D-T fusion is almost twice as energetic as P-B, but the real advantage is that it’s so much easier to do. The ignition temperature is enormously lower, and thermal radiation scales as the fourth power of temperature. Thermal radiation heat loss also scales with particle charge, and boron is much more highly charged than any hydrogen isotope, so the plasma radiates away heat like mad by the time you reach a temperature where the reaction occurs at a decent rate.

        So, they’re reliant on achieving a magnetic field you’d normally find only on a neutron star, to suppress radiation, and a plasma density higher than normal matter to make the plasma optically thick. The conditions in that pinch of theirs are more extreme than you’d find inside a hydrogen bomb! Just to make P-B fusion marginally feasible. It really is a tough reaction.

        I expect they could achieve D-T fusion easily enough, but then their test reactor would become radioactive, and working with it enormously more expensive.

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        • Right. Not only is it really tough to get a license to use tritium, with such a small device as ours, the neutrons would knock heck out of it. We will go right from the pure deuterium we are using now to pB11–soon!

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        • If LPP switches to D-T and they hit a world record Q then they would be able to raise enough capital to simultaneously pursue D-T and p-B. The machine wouldn’t become too radioactive after 100 pinches, probably more of an issue to handle T.

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          • There’s nothing in LPP’s machine to stop 14.1 MEV neutrons. I don’t know if their first shot with D-T would kill the entire crew, but I would not want to be anywhere nearby if they tried it.

            Brian didn’t mention General Fusion, who is even now building a prototype Magnetized Target fusion reactor in England. Their unique way of handling the neutrons produced makes them the only D-T fusion scheme in which I have any faith: I think tokamaks are a boondoggle. But I think that some form of aneutronic, probably p-B11 fueled, direct-energy conversion fusion reactor will be on line this decade. Fusion is only still 20 years out if we are waiting–and wasting money on–ITER.

  5. Well done! I am ever one of those people who refuse to be convinced that I won’t see fusion power overtake current generation methods well within my lifetime, though. But that’s more a personal problem, for me. 😉

    With that said, what about direct energy capture for fusion rather than turbine power generation? I don’t know enough about how it works to speak on its efficiency, but it would seem the way to go.

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    • In p-b11 fusion a boron-11 ion absorbs a proton, and instead of becoming stable carbon 12, contains more energy than it can handle, so it fissions (not sure why it’s called fusion) into three helium nuclei. Steer those through a copper induction coil, and as they slow to a stop their positive charge creates a current in the coil, which generates the magnetic field that slows and stops them; hence direct energy capture. No moving parts, no hot steam, no turbines, generators, recuperators … . In LPP’s drawings of their reactor, the induction coil is a tube maybe 6 inches by two or three feet.

      I have no idea whether a dense plasma focus will work as a fusion engine: I think they are used to initiate nuclear explosions, but that doesn’t have to “break even.” But if LPP can give us 5 MW in a ~ 6 ft. diameter sphere weighting 1.5 tons (add 1.5 tons water after you drop a reactor by small helicopter anywhere in the world you want one) for half a million dollars, they will solve the energy crisis everywhere forever. 5 MW is right for a locomotive, a tugboat; two to four of them would power an airliner with unlimited range, for a fraction of the cost of a jet engine, and you wouldn’t have to carry tons and tons of fuel. That would be so world changing that I, too, am a small investor with LPP.

      It does make me nervous that LPP Chief Scientist Eric Lerner spends a lot of time trying to debunk the Big Bang Theory, but I understand that another 7 or 8 groups around the world are working on DPFs. I hope they’re not all nutz.

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  6. Your data is very much outdated. NIF has recently had a gain of 70% and by an approximate Wallplug efficiency of the modern lasers of 10% you get a total efficiency of 7% making it 4 orders of magnitude more efficient than the other companies in your plot. The leading Scientist behind these results work now at or together with the private startup Focused Energy which should definitely be listed here.

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    • Yes, NIF (National Ignition Facility) had a nice pulse. Getting close to ignition. The laser pulse work for the laser startups (Focused Energy World, Marvel, HB11) could be promising.
      Have to get the fusion rate, energy return and pulse rates up. Things might work out. I will be covering all of the laser fusion work in a seperate video and articles.

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    • This is not exactly right. NIF had a fusion yield of 1.3 MJ and an input to the lasers of 400 MJ, so that is 0.3%, not 7%. To get net energy, more electricity out of the device than into it, you need at least 1000 MJ fusion energy, so they are a factor of 3,000 away. They did got a big increase though–25 times.

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  7. LPP Fusion is currently raising capital on wefunder.com I won’t post a link to the funding page but anyone can find it if they want to invest. As an investor in LPP I will say that it is a high risk, extremely high reward investment.

    Their current valuation is based on recent record setting improvements for plasma purity. Their DPF works best with a very pure plasma and they have achieved that by creating a plasma 10x purer than the Wendelstein stellarator (fantastic machine IMHO!). Currently they are reworking their switches/insulators to fire correctly and they have stated on their Facebook page that they want to switch to D-T fusion for some shots. I’m not privy to their planning but I strongly suspect that if D-T pinches are successful that their triple product will set records and their next funding round will be at a significantly higher valuation.

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