Nuclear Fusion Energy | Ian Hutchinson and Lex Fridman

maybe another distinction we want to try to get at is a difference between fission and fusion as you mentioned fusion is the kind of reaction happening in the sun so what's fission and what's fusion well fission is taking heavy elements like uranium and breaking them up and it turns out that that process of breaking up heavy elements releases energy what does it mean to be a heavy helmet it means that there are many nuclear particles in the nucleus itself neutrons and protons in the in the nucleus itself so that in the case of uranium there are 92 protons in each nucleus and even more neutrons so that the total number of nucleons in the nucleus nucleons is short for for either a proton or a neutron um the total number you know might be 235 that's u235 or it might be 238 that's u238 so those are heavy elements light elements by contrast have very few nucleons protons or neutrons in the nucleus hydrogen is the lightest nucleus it has one proton there are actually slightly heavier forms of hydrogen isotopes deuterium has a proton and a neutron and tritium has a proton and two neutrons so it has total of three nucleons in the new in the nucleus well taking light elements like isotopes of hydrogen and and not breaking them up but actually fusing them together reacting them together to produce heavier elements typically helium okay which is helium is a nucleus which has has two protons and two neutrons that also releases energy and that and that or reactions like that making heavier elements from lighter elements is what mostly powers the sun and stars both fusion and fission release approximately a million times more energy per unit mass than chemical reactions so a chemical reaction means take hydrogen take oxygen react them together let's say and get water that releases energy the energy released in a chemical reaction like that or the burning of coal or on oil or whatever else is about a million times less per unit mass than what is released in nuclear reactions so but it's hard to do it requires very high energy of impact and actually it's very easy to understand why and that is that those two nuclei if they're both let's say hydrogen nuclei one is let's say deuterium and the other is let's say tritium they're both electrically charged and so that and they're positively charged so they they like charges repel everyone knows that right so basically to get them close enough together to react you have to overcome the repulsion the electric repulsion of the two nuclei from one another and you have to get them extremely close to one another in order for the nuclear forces to overtake the electrical forces and and actually form a new nucleus and so one requires very high energies of impact in order for reactions to take place and those high energies of impact correspond to very high temperatures of random motion so that's why you can do something like that in the sun so we can build the sun that's one way to do it but on earth how do you create a fusion reaction yeah well nature engineering nature's fusion uh reactors are indeed the stars and uh they are very hot in the in the center and re and they reach the point where they release more energy from those reactions than they lose by radiation and transport to the surface and so forth and that's a state of ignition and and that's what we have to achieve to to give net energy it's like lighting a fire if you if you have a if you have a bundle of sticks and you hold a match up to it and you see smoke coming from the sticks but you take the match away and the f and the and the sticks just fizzle out that's not the reason they did it fizzled out is that yes they were burning there was smoke coming from them but they were not ignited but if you are able to take the match away and they keep burning and they are generating enough heat to keep themselves hot and hence keep the reactions going that's chemical ignition well what we need to do what the stars do in order to generate nuclear fusion energy is they are ignited they are generated enough energy to keep themselves hot and that's what we've got to do on earth if we're going to make fusion work on earth but it's much harder to do on earth than it is you know in a star because you know we need temperatures of order tens of millions of degrees celsius in order for the reactions to go fast enough to generate enough electricity to keep or enough energy to keep it going and and so um if you've got something that's tens of millions of degrees celsius and you want to keep it all together and keep the heat in long enough to have enough reactions taking place you can't just put it in a bottle you know plastic or glass it would be gone you know it's in milliseconds um so um you have to have some non-material mechanism of confining the plasma in the case of stars that non-material force is gravity so gravity is what holds a star together it's what holds the plasma in long enough for it to react and and and sustain itself by the the fusion reactions but on earth gravity is extremely weak i mean i don't mean to say we don't fall yes we fall but the the mutual gravitational attraction of small objects is very weak compared with the electrical repulsion or any other force that you can think about on earth and so we need a stronger force to keep the plasma together to confine it and the predominant attempt at making fusion work on earth is to use magnetic fields to confine the plasma and that's what i've worked on for much essentially most of my career is to understand how we can and how best we can confine these incredibly hot gases plasmas using magnetic fields with the ultimate objective of releasing fusion energy on earth and you know generating electricity with it and powering our society with it uh dumb question so on top of the magnetic fields do you also need the plastic water bottle walls or is it purely magnetic fields well actually what we do need walls um those walls must be kept away from the plasma because otherwise they'd be melted or the plasma must be kept away from them inside inside of them but the main purpose of the walls is not to keep the plasma in it's to keep the atmosphere out so if we want to do it on earth where there's air um we want the plasma to consist of hydrogen isotopes or other things the things we're trying to react and by the way the density of those plasmas at least in magnetic confinement fusion is very low it's maybe a million times less than the density of air in this room so in order for a fusion reactor like that to work you have to keep all of the air out and just keep the plasma in so yes there are other things but those are things that are relatively easy i mean making a vacuum these days is technologically quite quite straightforward we know how to do that okay what we don't quite know how to do is to make a confinement uh device that isolates the plasma well enough so that it so that it's able to keep itself burning with its own reaction so maybe can you talk about what a takamaka is the russian acronym from which the word takamak is built just means toroidal magnetic chamber so it's a toroidal chamber taurus is a is a geometric shape which is like a doughnut with a hole down the middle okay and so it's the so it's the meat of the doughnut okay that's the taurus um and it's and it's got a magnetic field so that's really all takamak uh means but the particular configuration um that we're the that is very widespread and there's the sort of best prospect in the least in the near term for making fusion energy work is one in which there's a very strong magnetic field the the long way around the doughnut around the taurus um so you've got to imagine that there's this doughnut shape with an embedded magnetic field just going round and round the long way the the big advantage of that is that um plasma particles are when they're in a in the presence of a magnetic field feel strong forces from the magnetic field and those forces make the particles gyrate around the direction of the magnetic field line so basically the particles follow helical orbits like like a following like a spring that's directed along the magnetic field well if you make the magnetic field go in inside this toroidal chamber and just simply go round and round the chamber then because of this helical orbit the particles can't move fast across the magnetic field but they can move very quickly along the magnetic field and if you have a magnetic field that doesn't leave the chamber it doesn't matter if they move along the magnetic field it does it means it doesn't mean they're going to exit the chamber but if you just had a straight magnetic field as you you know for example coming from um you know a helmholtz coil or or a bar magnet then you'd have to have ends it would come would come to the end ends of the chamber somewhere in the and the particles would hit the ends and and they would lose their energy so that's why it's toroidal and that's why we have a strong magnetic field it it's providing um a confinement against motion in the in the direction that would lead the particles to leave the chamber it turns out that then here we're getting a little bit technical but it turns out that a toroidal field alone is not enough and so you need more fields to produce true true confinement of plasma and we get those by passing a current as well through the plasma itself i can make sure it stays on track well that what that does is makes the field lines themselves into much bigger helices and that for reasons that are too complicated to explain that clinches the confinement of the particles at least in terms of their single particle orbits so they don't leave the chamber so when the particles are flying along this uh this this donut the inside of the donut uh are they what's where's the generation of the energy coming from are they smashing into each other yeah eventually i mean in a fusion reactor there will be deuterons and triti and tritons and they will be smashing in they will be very hot they'll be 100 million degrees celsius or something so they're moving thermally with very large thermal energies in random directions and they will collide with one another and have fusion reactions when those fusion reactions take place energy is released large amounts of energy is released in the form of particles one of the particles that's released is an alpha particle which is also charged and it's also confined and that alpha particle stays in the in the in the doughnut and heats the other particles that are in that doughnut so it transfers its energy to those and they it keeps them hot there's there's some leaking of heat all the time a little bit of radiation some transport and so forth there's also a neutron released from that reaction the neutron carries out four-fifths of the fusion energy and that will have to be captured in a blanket that surrounds the chamber in which we take the energy drive some kind of electrical generator from you know thermal engine um gas turbine or something like that and power the power you got energy so where do we stand where do we stand on getting this thing to be something that actually works it generates energy yep well um there have been experiments that have generated net nuclear energies or nuclear powers in the vicinity of um you know a few tens of megawatts for a few seconds so that's you know 10 megajoules that's not much energy it's a few doughnuts worth of energy okay yeah literal donut literally that's right um but um but we have studied how well tokamax can confine plasmas and so we now understand in in rather great detail um the way they work and we're able to predict what is going to be required in order to build a tokamak that becomes self-sustaining that becomes essentially ignited or very so close to ignited that it doesn't matter and and at the moment at least if you use the modest magnetic field values still very strong but but limited limited magnetic field values you have to build a very big device and so we are at the moment worldwide fusion research is at the moment in the process of building a very big experiment that's located in the south of france it's called eta i-t-e-r which means the way or just means the international tokamak experimental reactor if you like um and that experiment is designed to reach this burning plasma state and to generate about 500 megawatts of fusion power for hundreds of seconds at a time it'll still only be an experiment it won't put electricity on the grid or anything like that it's it's to figure out what whether it works and and with what the remaining engineering challenges are it's a scientific experiment it won't be engineered to run round the clock and and so on and so forth which ultimately one one needs to do in order to make something that's practical for generating electricity but it will be the first demonstration on earth of a controlled fusion reaction reaction for you know long time time period is that exciting to you yes uh it it it's been an objective that is in many ways motivated my entire career and the career career of many people like me in the field i have to admit though that one of the problems with eta is that it's an extremely big and expensive and long time to build experiment and so it won't even come into operation until about 2025 even though it's been being built for 10 years and it's been it was designed for 30 years before that right um and so that's actually one of the big disappointments of my career in a certain sense which is that we won't get to uh burning fusion uh reaction until well past the first operation of eta and whether i'm alive or not i don't know um but i certainly will be well and truly retired by the time that happens and so when i realized maybe some years ago that that was going to be the case it was a discouragement to me let's put it like that but if we can try to look maybe in a ridiculous kind of way look into a hundred years from now 200 years 500 years from now and we you know there's folks like elon musk uh trying to travel outside the solar system i mean the amount of energy we need for some of the exciting things we want to do in this world if we look again 100 years from now seems to be a very large amount so do you think fusion energy will eventually uh sometime into your retirement uh will be basically uh behind most of the things we do look i absolutely think that fusion research is completely justified in fact we should be spending more time and effort on it than we currently do but it isn't going to be a magic bullet that somehow uh solves all the problems of energy by the way that's a generic statement you could make about any energy source in my view i think it's a grave mistake to think that science of any sort is suddenly going to find a magic bullet for meeting all the energy needs of society or any of the other needs of society by the way but and we can talk about that by hopefully later okay um but but but but fusion is very worthwhile and we should be doing it um and and so my disappointment that i just expressed um was in a certain sense of personal disappointment i do think that fusion energy is a terrific challenge it's very difficult to bring the energy source of the sun and stars down to earth this does contrast in a certain sense with fission energy by contrast fission energy efficient to build a fission reactor proved to be amazingly easy you know we did it um within a few years of discovering nuclear fission people had uh figured out how to build a reactor and did so um you know during the second world war which is by the way fission is how the current nuclear power plants work yeah and so we have uh nuclear energy today because fission uh reactors are relatively easy to build you've got to have what's hard is getting the materials okay and that's just as well because if everyone could get those materials you know there would be weapons proliferation and so forth but it wasn't um all that long um after even the discovery of nuclear fission that fission reactors were built and fission reactors of course operated before we had weapons so i think nuclear power is obviously important to meet the energy challenges of our age it is completely intrinsically completely uh co2 emissions free and in fact the wastes that come from nuclear power whether it's fission or fusion for that matter are so moderate in quantity that that we shouldn't really be worried about them um i mean yes fission products are highly radioactive and and we need to keep them away from people but there's so little of them it's that keeping them away from people is not particularly difficult and so while people complain a lot about the drawbacks of fish and energy um i think most of those complaints are ill-informed um we can talk about you know the the challenges in the disasters if you like of uh of uh of fish and reactors but i think fission in the near term offers a terrific opportunity for environmentally friendly energy which in which in the world as a whole is rapidly being taken advantage of you know china and india and places like that are rapidly building fission plants we're not rapidly building fission plants in the u.s although we are actually building two at the moment um two new ones um but we do still get 20 percent of our electricity from fission energy and we could get a lot more so it's clean energy so it's clean energy now now again the concern is there's a very popular hbo show on uh just came out on chernobyl uh there's the three mile island there's fukushima that's the most recent disaster so there's a kind of a concern of um yeah i mean nuclear disasters is that what do you make of that kind of uh concern especially if we look into the future of fission energy based reactors well first of all let me say one or two words about the contrast between fission and fusion and then we'll come on to the question of the disasters and so forth fission does have some drawbacks and there and they're largely to do with four four main areas one is do we have enough uranium or other fissile fuels to to supply our energy needs for a long time the answer to that is we know we have um enough uranium to support fission energy worldwide for thousands of years but maybe not for millions of years okay so that's resources um secondly there there are issues to do with wastes fission wastes are highly radioactive and some of them are volatile and so for example um in fukushima the the problem was that some fraction of the fission waste were volatilized and went out as a cloud and and polluted air areas with um cesium 137 the strontium 90 and things like that so that's a challenge of fission um there's a problem of safety uh beyond that and that is that um in fission it's hard to turn the reactor off when you turn when you stop the nuclear reactions there is still a lot of heat being liberated from the fission products and that is actually what the problem was at fukushima the fukushima reactors were shut down the moment that the earthquake took place and they were shut down safely what then happened after that fukushima was you know there were there was this enormous tidal wave um many tens of meters high that came through and destroyed the electricity grid feed to the fukushima reactors and their cooling was then turned off and it was the after heat of the turned off reactors that eventually caused the problems that led to release and so that so that is that's a safety concern and then and then finally there's a problem of proliferation and that is that fission reactors need fissile fuel and the technologies for producing the under enriching and so forth the fuels can be used can be can be um by by bad actors to generate um the materials needed for a nuclear weapon and that's a very very serious concern so those are the four problems fusion has major advantages in respect of all of those problems it has more uh longer term um fuel resources it has far more benign waste issues the react the radioactivity from fusion reactions is at least a hundred times less than it is from fission reactions it has um no none essentially none of this after heat problem because it doesn't produce fission products that are highly radioactive and generating their own heat when it's turned off in fact the hard part of fusion is turning it on not turning it off and and finally you don't need the same uh fission technology to do to make fusion work and so it there it's got terrific advantages from the point of view of proliferation control so those are the those are four main issues which make fusion seem attractive technologically because they address some of the problems of fish and energy i don't mean to say that fission energy is overwhelmingly problematic but clearly there have been catastrophes associated with fission reactors fukushima actually is i think in many ways often overstated as a disaster because after all nobody was killed by the reactors essentially zero and that's in the context of a disaster a tsunami that killed between 15 and 20 000 people instantaneous more or less instantaneously so you know in the scale of risks um one should take the view that uh in my in my in my estimation that um fish and energy came out of that looking pretty good okay of course that's not the popular conception okay yes it's gonna i mean with a lot of things that threaten our well-being we seem to be very uh bad uh users of data we seem to be very scared of uh shark attacks and not at all scared of car accidents and this kind of miscalculation and i think from everything and i understand uh nuclear energy efficient based energy goes into that category it's one of the safest one of the cleanest forms of energy and yet the pr uh whoever does the pr for nuclear energy is not uh has a hard job ahead of them at the moment well i think part of that is their association with nuclear weapons right because when you say the word nuclear people don't instantly think about nuclear energy they think about nuclear weapons and and so there is you know perhaps um a natural tendency to do that but yes i agree with you people are very poor at estimating risks and they react emotionally not rationally in most of these situations you

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Length: 27min 44sec (1664 seconds)

Published: Sat Aug 01 2020