Simple Answers for How Far Away is Tokomak Nuclear Fusion? #fusion #nuclear

How far away is Tokomak nuclear fusion? People get confused by the terms megajoules and various kinds of breakeven metrics.

There are simpler ways to look at it.

How fast is the progress?

What has to be achieved for a commercial nuclear fusion reactor?

The JET tokomak reactor has been working for a few decades. JET set record in 1997 by producing 21.7 Megajoules. In 2022, researchers in the EUROfusion consortium released a record-breaking 59 megajoules (MJ) of fusion energy. This was also done at the JET facility. JET was operated for 5 seconds to get 59 megajoules. It needs three times as much energy to heat the fuel. Twenty five years passed between the two records.

59 megajoules is 13 kilowatt hours. A typical US house uses 30-kilowatt hours in a day. The first nuclear fission reactor powered lightbulbs in 1951 and started powering a town in 1952. The 59 megajoules was just waste heat that could not be captured and used. It was detected and measured as a science experiment.

Billions of dollars have been spent on ITER (International Tokamak) and continue to be spent on ITER. ITER was started by US President Ronald Reagan and Russian leader Gorbachev. ITER was started in 1988 and they started building it in 2007. ITER might hit its current total budget of $22 billion but others think it will cost $65 billion. The plans is it will produce around 500 megawatts of power continuously for 400 seconds while only consuming 50 MW of energy to heat the fuel. This mean the reactor produced 10 times more than fuel heating. However, the ITER reactor will need 300 megawatts of electricity to produce 50 megawatts of heat. Heat would have to be converted back to electricity. This would mean getting back 5-10% of the electricity. ITER could start initial tests and operation in 2027 but it could take deep into the 2030s for it reach the goal of 400 seconds of energy-losing operation.

There are 31,536,000 seconds in a year. A normal US fission nuclear reactor operates for over 90% of the year. This means a fission reactor will operate for 28 million seconds for every year. Most are generating 1000 megawatts or more.

The Tokomaks would have to get stabilized to operate for over 5 million times more in a year. The plan is to use another $15-50 billion to get 80 times longer operation from 5 seconds to 400 seconds.

They would then follow up with the DEMO reactor. This could start operating in 2051. It might barely breakeven. It would generate about 750 Megawatts of electricity but it would need about 500 Megawatts of power. DEMO would not operate for very long either. In order to get to operating 50-90% of the time for a commercial reactor another Tokomak reactor to create stable commercial operation would be needed.

Tritium Needed

So this sounds like another 100 years of work at the current pace. This is to achieve Deuterium-Tritium (D-T) nuclear fusion. Tritium is important. Tritium is not produced in nature (on earth, other than trace amounts from cosmic rays). A commercial D-T fusion plant producing 3 gigawatts of electricity will burn 167 kilograms of tritium per year. There is about 20 kilograms of tritium in the world. DEMO would use 4-15 kilograms of tritium.

A commercial D-T fusion plant producing 3 gigawatts of electricity will burn 167 kilograms of tritium per year. We harvest about 1.8 kilograms of tritium every year from CANDU nuclear fission reactors. Those CANDU reactors are decades old and many are scheduled for shutdown. Most do not have Tritium harvesting set up.

423 nuclear fission reactors are currently operating. Japan could turn on a few more that they had shutoff. The worlds nuclear fission reactors produce 380 Gigawatts of power or about 2700 TWh each year. If the Tokomak nuclear fusion reactors matched the electricity from thecurrent nuclear fission reactors then about 21,000 kilograms of Tritium would be needed every year. This is over 1000 times as much as we have today.


The work on Tokomak fusion is small milestones over decades. They could hope for a commercial reactor by 2100 but then they would also need to scale up the levels of tritium by thousands of times.

Unlimited power except for getting the Tokomaks to work 5 million times more in one year than they currently do. Unlimited power except for the need for many tons of Tritium that we do not have.

Also, if you do solve the Tritium availability problem, then you will have a massive proliferation problem. 4-5 grams of Tritium boosts the explosive power of a nuclear weapon from 300 tons of TNT equivalent up to 100,000 tons. You would thousands of times more of one of the main materials for nuclear bombs.

I am more hopeful about other approaches to nuclear fusion like laser pulse systems. I also like advanced nuclear fission like molten salt fission power systems. There has been funding of over $5 billion into private commercial fusion projects.

I track all of the nuclear fusion and advanced nuclear fission projects.

73 thoughts on “Simple Answers for How Far Away is Tokomak Nuclear Fusion? #fusion #nuclear”

  1. Just a few thoughts on the fusion problem.
    1 the fusion attempt with H isotopes are not like the reaction in our Sun. Take a look at astrophysics.Pure H H fusion of any isotope is the hardest process in the universe!!! The only stars that do it are giant blue stars, 300 to 600 time the mass of our Sun. Our Sun is dirty, with heavy ions drasticly shifting velocity to the tiny H ions, while the rest of the plasma has a cooler temp and lower pressue. This is what we need to mimic.
    2 As testament to the above, follow our own success. The only successful fusion we have harnessed with massive energy yeild, happened in a dense plasma full of fissions heavy split ions and massive neutron flux.
    Using the lessons from stars and our own hydrogen bombs is likely the fastest way to viable commercial fusion. Mimicking blue giant stars is not!!!

  2. oh and laser pulse systems are nothing but PR

    no plausible path to any sort of useful energy production at any price

    but they’re great at spending money and generating headlines

      • That was only positive energy when measuring energy in and out of the fuel target. Laser energy hitting the fuel target and heat generated. The energy going into the system to produce the lasers was far higher.

  3. look at the most advanced ARES vaporware and calculate the plant size relative to fission

    order of magnitude larger = order of magnitude more expensive

    that’s before we talk about the far greater complexity and the little fact that even at .1% utilization for basic research the ITER shielding had to be replaced after a few years, meaning there’s no conceivable material that could economically stand actual usage at current energy prices

    barring a high-beta breakthrough in FRCs or polywells, it now appears increasingly likely humans will experience three dominant energy regimes:

    cheap fossil fuels
    slightly more expensive fission
    vastly more expensive fusion

    fortunately fission lasts thousands of years so the unobtainium might be obtained by then

  4. When I was young I found a British book – published in 1950 – that explained why commercial fusion power was only 10 years away.

    Seems like it has always been just 10 years away

  5. Statists will always argue it is worthwhile to throw other people’s money (taxes) at dozens of fruitless endeavors for the ‘public good’. These can be aircraft carriers that won’t make it 10 days into world war 3 or fusion experiments that can be picked apart by an undergraduate’s hand calculations. It takes a certain amount of maturity to shrug your shoulders and get back to work on real things, while an army of ‘boffins’ work on a giant vacuum tube in southern France. Bad science and waste is everywhere you look… Surest way to get rich is to tap into the mainline of government contracts – corruption is king!

    • Every scientific exploration produces unexpected benefits far exceeding the the initial cost. What the US spends on “bleeding edge” research represents a very small portion of the national budget compared to defense and entitlements.

      • Every?
        The rule of thumb is that 1 out of 10 ideas is worth prototyping, only 1 out of 10 prototypes produces the desired results, and only 1 out of 10 of those is better than the current solution.

    • The Sun is natural nuclear fusion, that’s why solar panels ends so called energy crisis. But they want to be feel like Gods by constantly improving Technology instead of evolution, less technology. Now the environment is more cancerous because of radiation from man made..

      • nuclear fission reactors reduced the amount of coal power used by 15% for the past 50-60 years. 40-70 billion tons of CO2 have been avoided and billions of tons of water and air pollution. Over 2 million lives saved from avoided air pollution. 150,000+ TWH generated from 1950s to today. 150,000+ TWH would have needed 20 billion tons of coal. Today it is 880 million pounds of CO2 per TWH. 440,000 tons of CO2 per TWH. 60-100 billion tons of CO2. More CO2 was avoided in the early decades when there was more coal usage.

      • Far far more people have died from coal burning power plant pollution, then all of the nuclear incidents from power plants and weapons combined. The problem with nuclear fission is political! It cost a lot because of regulations and the push develop weapons leading to potentially unstable designs. If the effort was made to continue with liquid salt thorium reactors, instead of killing the functional reactor and project, we could have reactors that burns the current waste and requires power to stay critical, otherwise it turns itself off.

        To really make the Green Dream true, we need to get rid of several billion people. Who gets to decide?

      • Pfft, solar? Solar panels, even with all the advancements made in the last 30 years are WOEFULLY inefficient, require 1000’s of panels and HUGH areas of land to be cleared in order to achieve anything approaching useful.

        Are you worried about man made contamination of the environment James? Well your lauded solar panels are so toxic that they are pretty much unrecyclable (well can be, just at 100 times the cost of their manufacture – and who would do that?) Do you know what they are doing with old, useless and broken panels James? They are simply stacking them up in warehouses and the more unscrupulous operators (China) just dig a hole and bury them.

        No James, fusion is the only way forward. Yes there has been a lot of promises made and not achieved, but as the article noted, progress has come in small steps. Speaking of non-achievers, just imagine if the morons of this planet hadn’t wasted trillions of dollars to, *ahem* “Stop Global Warming” TM Just imagine if all those fruitless dollars were funnelled into the fusion projects instead. Imagine the advances we would have now.

        Oh well, no such thing as a time machine and the glow-bull woremyn religious zealots are still destroying the environment with their useless gestures. I need a beer.

        • Let’s play devil’s advocate here for a minute.

          We do have a perfectly working fusion reactor, it’s output is tremendous and gives enough power output to satisfy the whole world’s energy needs, we call it the sun.

          I agree capturing this energy on earth through solar panels is not the greatest way forward, but I would like all the money being given to ITER to be redirected and put into research of solar energy being collected in space and microwaved back down to collectors on earth.

          China is pushing the idea and is putting in a lot of research into the idea of collecting solar energy from space.

          We know the sun gives out sufficient energy as a fusion reactor, we do not know if ITER will ever break even or produce more than enough additional energy to heat a coffee pot.

        • All the bst oriented roofs and parking lots are already nature dead zones and heat radiators. Putting solar panels on them may be the best of a lot of compromises .

    • But the possibility of Clean Air, and less noise, all around you is so tempting, especially for city dwellers. How can we not want Hydrogen and Fusion.

      • You don’t need to go all the way to hydrogen and fusion power to get clean air (either CO2 or other pollution) and low noise.

  6. Tokamak and tritium is nice for research, some systems with pb11 fuel could be producing electricity much sooner…

    • PB11? I wish LPP Fusion the best of luck, but that’s a really hard nut to crack, because,

      1) It’s a relatively low energy output reaction. DT puts out 17MEV per reaction, PB11 only 8.7.

      2) It’s a very high temperature reaction; about 2000 times hotter than DT.

      3) The reactants have relatively high atomic weights, “Z”, which means they radiate heat like crazy.

      4) And remember, thermal radiation is T^4, so that high Z combined with the higher temperature means trillions of times more thermal losses.

      The only way LPP gets to thinking they can pull it off is by achieving densities and magnetic fields normally only found in a neutron star, to cause a quantum phenomenon to suppress radiation, and have a radiatively “thick” plasma. And even then they plan on scavenging every last bit of efficiency in power conversion, just to have a prayer of reaching engineering breakeven.

      I wish them well, but, man, they picked a tough one to pull off. It’s like a startup deciding that their first sounding rocket should be an interstellar ship.

      • Honestly I prefer LPP’s “significant physics and engineering issues that lead to economical energy” in contrast to Tokamak’s “significant physics and engineering issues that will never lead to economical energy”.

        • Well, for fundamental physics reasons, I doubt LPP will get their reactor working, but if they do it could be cost effective.

          OTOH, for fundamental physics reasons I’m fairly confident they can eventually get Tokamaks working, but don’t believe they could ever be cost effective if they do.

          Fission, OTOH, both works and, if the regulators can be persuaded to be sane, can be cost effective.

          • No arguments here. There is no reason why we can’t pursue fission while also doing R&D in fusion. If anything fission is the reliable clean energy supply that fusion would have to compete with.

    • Tokamak is only one approach to fusion. Others are also in the works. There are also much safer fission reactor technologies in the works which can actually use today’s nuclear waste as fuel.

    • lol yeah tritium breeding is among the smallest technical problems

      once you have a fusion plant it’s trivial to use the neutron flux to make it

      much bigger problem is that neutron flux also destroys your shielding really fast whether you’re breeding or not

      • Trivial? How much Li6 is in the world? They are going to have to scavenge and hope not even lose more than a few percent. Even then can youpoint me to where this has ever been done? No you can’t. I do not think trivial means what you think it means.

  7. Brian, Deuterium and Helium-3 isotopes can be used instead of Tritium. The reaction will require 200 million degrees plasma temperature which is attainable. Helium-3 is rare on Earth but is abundant on the moon. So is the future of nuclear fusion all in the hands of Elon Musk and the Starship which can economically bring Helium-3 back to Earth from the Moon ?

    • I specifically was referring to Tokomak fusion and the ITER approach as being slow. I cited Deuterium-Tritium because of 34+ nuclear fusion companies over half are targeting deuterium-tritium. The Deuterium-Deuterium or Proton-boron types do not have to solve the Tritium supply.

      • You can make Tritium with a Lithium blanket.
        And you can make Tritium by fusing Deuterium. Several of the D-T fusion startups have a path where they can use D-D bootstrapping to make enough Tritium for startup.

    • We already know that we can accomplish fusion with deuterium and lithium hydride. The problem is containment. Magnetic bottles (tokamak) use incredible amounts of electricity to contain plasmas. Lasers can fuse hydrogen into helium on a very small scale, but scaling up that technology has its own challenges.

    • lol if you think shielding is an issue for D-D or D-T just wait till you see what He or (God help us) P-B11 do to your reactor

      no possibility of an aneutronic tok, the thermal tail will produce tens of thousands of times more neutrons from side reactions anyway

  8. I thought it was intended that Tokomaks would include a lithium jacket in which the neutrons from the fusion reactions would breed tritium. That does not seem to be taken into account in what Brian wrote. Am I mistaken about that intent, or do the numbers indicate that would not breed enough tritium to supply at least as much tritium as the Tokomak consumes?

    Of course, we still would face the problem of creating the initial supply of tritium for the first non-experimental Tokomaks.

    I was unaware that tritium posed a danger in regard to nuclear weapons proliferation. I thought it was lithium hydride that was used to enhance the power of a fission bomb. The WW2 fission bombs did not use tritium, did they?

    • They do use tritium gas in weapons – the so called ‘boosting’. That’s about all we *know*, officially – that it is used. Perhaps the quantity of boosting gas introduced to the gloryhole of one of these demonic devices is a straightforward mechanism for the ‘dial a yield’ we hear of for the fission bomb. More DT, more fast neutrons, more multiplication more excursion before disassembly. The T gas is made at TVA’s Watts Bar 1 PWR by irradiating lithium bearing inserts (TPBAR) in the guide tubes of fuel assemblies. Guide tubes otherwise receive suppressive boron inserts of similar design (WABA) or control rods if placed under a rod drive.

      There’s not a lot of tritium produced, and there’s not a lot of inventory, and it doesn’t stay on the shelf particularly long. The decay product helium 3 should be pretty useful too.

      ITER is cool, but just a sideshow. Way too complicated compared to a fission pile.

      • I don’t think dial-a-yield relies on messing with tritium boosting. This is not undoable; once the tritium is in there it is not easy to take it out.

        Small nukes since the Swan device have often used the one-point-safe “flying plate” design. The velocity of the plate is much slower across the air gap than even a slow high explosive, so you only need two points of ignition and an ovoid shaped plate.

        Some of the early designs were *almost* one point safe but had a nuclear yield of tonnes to kilotonnes in tests. I think what they did is to make a one-point safe design and control the yield by just worsening the timing slightly. If one side ignites a few microseconds earlier the pit will be squeezed in a slight eliptical/peanut shape, but not bad enough to get no yield. If you can dial the delay; essentially just adding a small length of wire in the same fashion as a potentiometer, you can detune the firing signal to one of the exploding bridge wire detonators very slightly.

        Then it is just a matter of doing some tests and some calculations to figure out what yield to mark and where on the dial.

        • I believe the DT gas is added to the cavity immediately prior to delivery – the gas reservoir is onboard.

          If anybody knew for sure they wouldn’t be speaking openly about it on the internet. Considering DT gas fuses most easily at ~50,000K, the neutrons added by fusion boosting would be rather late. Source neutrons from boosting would be a huge step-jump in the neutron population of a runaway reaction already underway.

          • It is true that the DT-container is on or in the device. I’m not sure if they add the gas during fusing or somehow do it automatically after the device has been set, but it is not easy to add with precision a certain amount of tritium and it does not greatly control yield of the device.

            The fact that you need tens of millions of kelvins (>1 keV) to even start fusing D-T at low rates means that fission has to happens before fusion. You will therefor have a device that is significantly above 1 critical mass and gets a big nuclear yield *regardless* of whether the device is boosted or not. I don’t see how you can make a fission device so barely critical that boosting can affect yield more than a factor of a few. Dial-a-yield devices usually have yields between tonnes to many kilotonnes. That’s a big range that seems more easily achievable by messing with timings; either of the detonators in the implosion system or maybe when and how many neutrons are injected by the neutron generator.

    • Sure, the plan is for tritium breeding, and that’s fine once the steady state is achieved.

      But not only is the world tritium supply kind of small for starting these reactors up, the situation is getting worse year by year, in part due to the NRC’s refusal to authorize CANDU reactors in the US, those reactors being the primary source of it.

      And even under ideal circumstances a working fusion reactor would only breed a tiny excess of tritium, barely enough to account for losses in storage. (Tritium decays into helium3.)

      So it’s kind of, you could run these reactors if you were already running them, but increasing the number rapidly requires an excess supply of tritium that you wouldn’t have. And the experimental reactors, which don’t breed tritium efficiently, would use up the world stockpile very rapidly.

      • Why would “the NRC’s refusal to authorize CANDU reactors in the US” be a thing? Those reactors do not have better overnight construction costs or make power more cheaply than the US LWRs. CANDU fuel economy is within 10% of the LWR kgU/MWd too, since the discharge burnup of LWR is 10x greater while the ore requirements are basically the same with only 12% of that material getting irradiated. Nobody wants a CANDU except nations convinced of fuel security FUD arguments that Iran demonstrates aren’t necessarily valid.

        And while CANDU may make gobs of Tritium, it is diffuse and everywhere in the coolant and would therefore be difficult to harvest, and that is why the DOD makes Tritium from lithium under irradiation in commercial PWRs. Most of the Tritium stays where it was made in the latter scenario. In the former scenario, the tritium is escaping everywhere.

        • As a practical matter, CANDU reactors seem to be the most economical source of Tritium at the moment, because they produce it as a natural byproduct of operation, and the only cost is the cost of extraction, which they have to do anyway. (To keep the heavy water CANDU reactors rely on as a moderator from becoming dangerous to handle.)

          The significance of the NRC refusing to license them is that people actually DID want to try building CANDU reactors in the US, whatever you think of their merits, and they’re a very well proved out form of reactor, and the NRC still wouldn’t approve them. It’s a great demonstration of how the NRC is dysfunctional, which just incidentally impacted tritium supplies.

          • The CANDU don’t ‘extract’ tritium from the coolant – instead it diffuses out of the system like hydrogen escapes every container given long enough. Being detectable, that leaking tritium scares people (just because it is detectable). There are sub-gram quantities of tritium in a 100,000 gallon reactor coolant system.

            Not sure why you think we should be making a bunch of tritium, where the injustice is, or how the way it’s actually done is “stupidly expensive” versus the Brett knows better way of extracting milligrams of tritium from kilotons of heavy water in another country’s reactors…

          • CANDU reactors can inherently rapidly increase power during certain types of accidents/events, unlike conventional water reactors that inherently shut themselves off. U.S. reactor regulations require the latter.

            Also, it is relatively easy to create plutonium for bombs using CANDU reactors, as fuel is easily shuffled in and out of the core. I believe that is what India actually did in the past.

        • And do you not understand that the DOD doesn’t use lithium rods in light water reactors to produce Tritium for our nuclear arsenal because of it being an economical way of doing it?

          They do it that way because they don’t have CANDU reactors, and only two countries produce Tritium commercially: Russia and Canada. And neither is willing to sell it to us for weapons purposes.

          So we make it the stupidly expensive way, instead.

          • Simply not correct. It is impractical to the absurd to think that getting trace tritium out of heavy water is a better way to get it than just irradiating lithium in stainless steel tubes like they do in practice. There is no way to concentrate the trace tritium impurity in a CANDU – it is silly that you think so.

            • “There is no way to concentrate the trace tritium impurity in a CANDU – it is silly that you think so.”

              I’m not quite sure why you’re so committed to denying that Canada is, in fact, a major world supplier of tritium, derived from CANDU reactors.

              Seriously, where did you think ITER was supposed to get their tritium? From the Darlington plant, in Ontario! Where they are actually doing what you claim is silly to think is possible. Since 1989! I’d include a link to the Darlington nuclear generating station homepage, but I don’t want this comment to disappear into moderation for who knows how long. You can find it yourself.

              It’s true that they could further increase tritium production by using lithium rods. But they’re producing it right now, extracted from the heavy water moderator. About 130g/year per reactor.

              • Just when you thought people couldn’t find a harder way to do something you find out that Darlington has a side business since 1989, selling priceless, yet basically useless, tritium.

                Ok. Doesn’t make it the easy way to do it, which would be to skip the chemical processing plant and irradiate lithium slugs in a PWR.

                • The key point is that they’re producing it anyway, because otherwise the heavy water gets radioactive enough to be a pain to work with. That makes it essentially a free byproduct, pure profit, because the expense is already part of the overhead of running the reactor.

                  Other reactor types you have to go out of your way to get tritium, it’s extra trouble. Sure, you can argue that it’s easier to get a high concentration of tritium out of irradiated lithium than a low concentration out of water, because it’s straight chemistry, no isotope separation, but I think you’re exaggerating how hard it is for them to concentrate it. Sure, it’s chemically the same as the hydrogen, but the mass difference is huge, separating tritium from heavy water is absurdly easy as isotope separation goes.

                  The other issue, of course, is that there are ridiculously stringent anti-proliferation treaty clauses having to do with producing tritium in light water reactors. Totally a separate issue from the technical ones, but they’re why the US only does it in one specific reactor that fits in a little gap in the treaty coverage. There would be serious international law issues with expanding light water reactor production of tritium.

                • It’s done commonly enough that you can buy turnkey systems to do it, and that a lot of research is going into doing it cheaper. Because wanting tritium for fusion reactors isn’t the actual driver for wanting the capability, rendering large quantities of tritium contaminated waste water legally safe to release into the environment is.

                  You do it because you want the water ‘detritified’ and then you’ve got this tritium you can sell. Win-win!

      • This assumes it is very hard to achieve significant DD fusion in tokamaks, so all the tritium has to be supplied from the breeding blanket. This is not necessarily true. Before ITER it took about 15 years to increase the fusion triple product by a factor of 100; which is about the different in reaction rates between DD fusion and DT fusion.

        ITER is so large and such a major international cooperation using outdated 1990’s technology that the rate of improvement can’t but collapse.

        It is still possible that stellarators or a smarter tokamak design can overtake it, but this would likely require cancelling ITER; the giant cuckoo that is sucking up all funding and fusion researchers and preventing them from doing something more useful.

        • I could not agree more, there is so much research going on around the world and this research is actively making advancements in reactor design and duration times of nuclear fusion.

          Iter is in danger of just becoming one of the greatest money black holes ever created .

    • You are correct. As with thermonuclear warheads, lithium hydride is the component used to produce tritium — not because it is more dangerous but because it is much more rare that deuterium, and harder to produce.

  9. Does the power economics work out better for the spherical tokomacs being developed with high temperature superconductors like SPARC at MIT and STEP in the UK? The cycle time to build this should be much faster than ITER. They are smaller, cheaper and faster to manufacture. Also the Lithium cladding acts as a means to breed Tritium to make the fusion reactors self sustaining. Sure there are a lot of unknowns, this is bleeding age engineering.

    • The problem with lithium breeding is that the D-T reaction produces 1 neutron, which encountering Li6 produces one T. So from the very start you have no room for losses.

      To counter this they introduce Be, which on being struck by a neutron can fission to two heliums and two neutrons. It also has a side chain that produces tritium and a neutron, and another that produces tritium and lithium 6, but no neutron. So it multiplies neutrons, but with a multiplier of less than 2.

      The neutron gain allows you a bit of room to keep things balanced even though you have losses, but not a lot of headroom, you still have to be very efficient in your neutron use, and the amount of available tritium for starting new reactors only grows very slowly.

      Fundamentally, rolling D-T fusion out is critically reliant on having fission reactors producing tritium as a byproduct. And regulators have disfavored tritium production for weapons proliferation reasons, so the world stock of tritium is really small compared to the amount needed to start up a fusion reactor.

      Really, if we were going to start using D-T fusion in a couple decades, as a practical matter we’d need a crash program of producing tritium in fission reactors, TODAY. And it would require so much fission power that you’d really end up wondering, “Why were we planning on using fusion reactors, again?”

      • Roughly only 5% of lithium found on earth is Lithium-6, while 95% is Lithium-7. Lithium-7 plus a neutron creates Tritium and remits a neutron. If this is the case doesn’t natural non-isotopically purified Lithium act as its own breeder? Or am I mistaken?

        • It’s a matter of cross section: Mostly neutrons just scatter of Li7, without ever reacting. Li6 has a much higher reaction cross section.

          Also, when Li6 absorbs a neutron and produces tritium, that’s an exothermic reaction. It adds 4.6MEV to the energy of the incoming neutron.

          Li7 absorbs a neutron and produces tritium and a neutron, but that’s an endothermic reaction, it actually consumes 2.5MEV per reaction!

          So the bottom line is that Li7 really is lousy for breeding tritium in a power producing reactor.

      • I agree you about tritium separating. Chemical reactions where tritium is involved instead of hydrogen or deuterium are significantly slower, and it is a good base to separate it. Also there are physical methods to do it so it does need expensive centrifuges to do it. Of course it needs a lot of energy but the price of tritium covers it.

    • Sounds like Brian is saying, the energy of the future for the next century.

      The private sector probably would have given up on Tokomaks decades ago. It doesn’t appear that, even if you could get one working, they’ll ever be cost effective, and they’ve been consuming research money that could have fully funded twenty different approaches.

      Or have vastly improved nuclear fission, which we already know we can make work.

      • Tokomak and Tritium are about 100 years away in terms of solving the technical problems and getting it to meaningful scale. The never aspect is that other major energy solutions can kill the need for it.

        • A century away? I doubt it. When the Wright brothers took their first powered flight, they could not have guessed humans would be standing on the moon less that 70 years later.

          Likewise, when we bombed Hiroshima in 1945 with a 20KT device, no one would have guessed that a 100 megaton device would exist 25 years later.

        • The Universe runs on gravitationally initiated nuclear fusion. There is no more efficient energy source. Maybe it will take 100 years, or maybe we will abandon the technology but, short of collecting the energy directly from the sun, harnessing fusion is the holy grail.

          • yep what makes the Sun hot is its awesome gravitationally-driven containment

            ironically the Sun is a terribly inefficient reactor by Earth standards, only puts out as much energy per mass as a compost heap

            good thing too or it wouldn’t have have lasted this long 🙂

            here on Earth, go high beta or go home!

Comments are closed.