 Hello, I'm Dr. Melanie Windridge and I'm a plasma physicist, so a plasma physicist is just somebody who works with plasmas Plasma is just a charged gas or the fourth state of matter so one up from a gas really, but there's definitely a strong nuclear force. I work in fusion research and Fusion because of the high temperatures that we need to to make fusion occur We're working with plasmas all the time because any gas that's about a hundred million degrees or as hot as the sun Is going to be in a plasma state. So what we're trying to control is is a plasma I like the fact that in fusion we're trying to do something You know, we're actually trying to make a new source of energy You know, there is an end point and and I really like that I really like the fact that we're working towards something and that's the challenge That's what I really like about fusion Hello everyone You're all feeling okay? Yes? Good. So today we're going to be talking about fusion And I'm a plasma physicist Now most people look at me a bit blankly when I say that because most people don't know what plasma is But let's have a show of hands. Who here has heard of plasma? Put your hands up. Oh Good quite a lot of you What about how many people know what plasma is? Yeah, some of you That's great Well, what about fusion? Who can tell what the word fusion means? Anyone? Is it the joining of two or more things together? Yes, that's right So yeah, exactly right joining of two or more things to form a single Entity and today we'll be talking about nuclear fusion the reaction that powers the Sun and the stars And first of all, I'd like you to imagine something for me So imagine that you're outside on a really hot day a bit like some of the ones that we've been having lately And you're lying on the grass in the Sun. You can feel the Sun on your face feel the warmth of the Sun and all that energy Now imagine the Sun itself The Sun is a huge ball of plasma That's undergoing fusion reactions to sustain it and imagine the particles inside the Sun They're all zooming around randomly crashing into each other some of them are fusing to make bigger particles And now imagine taking a little piece of the Sun and bringing it to Earth Because we want to use it to make clean energy for mankind But there's a problem Because without the huge mass of the Sun without the huge gravitational pressure Our little piece of sunshine is escaping and cooling So we need to find some way to keep it trapped And so what are we going to do? Well, we can't put it in a box because it can't touch anything It's too hot so we need to find some other way and what we do is we use something like this This is a tokamak. It's a machine that we use to do fusion And we're going to talk a bit more about tokamaks and what they are a bit later But first of all, I just want to give you an idea of the scale of these machines the size of them Because this is a workman who's working on the machines This is Jet. It's the biggest fusion experiment in the world And this guy is an ordinary man. He's not a midget So this gives you an idea of just how big these machines are This is the inside, the very central area of the machine again With the man to show you the scale So fusion is a huge project Making fusion on earth is a massive undertaking So let's have a think first of all why we need fusion So this slide should give you a clue But can anyone tell me why we need a new source of energy? All the other energy is running out Okay, so the other energy is running out So the fuels, fossil fuels that we currently use to provide our energy are running out So we're going to need something else Another reason is that the population is always increasing And so our energy demands are also rising And there are large countries in the world like China and India who are industrialising And they're rapidly increasing their energy demands So on the whole, worldwide energy demand is going up And the fuels that we're using are running out But we do have some alternatives, don't we? There are some renewable sources that we can use So who can tell me, you can shout out if you like Who can tell me some renewable sources? Solar, wind, wind I've heard Sorry, tidal, yes, great, thank you Did I hear biomass as well? That's a good one, biomass as well Alright, so lots of different renewable types of energy That's great However, there are some problems with the renewable sources of energy One of them is that what's known as low energy density Now that means that if you've only got one windmill or one solar panel Then you're not going to get very much energy You need to have a lot of them And they take up a lot of space For example, to get the same amount of energy As you get from, say, one coal-fired power station Or a future fusion power station using wind We need to have about a thousand windmills Big windmills that have about a hundred metre bladesband So think how much space that would take up So that's quite a problem Especially if we've got increasing populations The other problem is that they're intermittent So when the sun's not shining or the wind's not blowing Then you don't have any energy So we also need to work on storage solutions If we're going to really heavily rely on renewable energy Now, I'm not saying that we shouldn't use renewables I think we should use whatever we can But it's questionable whether or not renewables will be able to satisfy the rising energy demands And this is why we need something like fusion That will produce a lot of energy Now fusion produces huge amounts of energy Just one kilogram of fusion fuel produces as much energy As 10 million kilograms of fossil fuels That's 10 million times as much energy So if we think about what this means for a power station A fusion power station will be able to operate Using one kilogram of fuel per day That's about a big bag of sugar In weight A coal-fired power station Uses several hundred truckloads of coal per day So that's the big difference in the amount of energy that you can get Fusion produces huge amounts of energy It also doesn't create any greenhouse gases Or any long-lived radioactive waste And the fuels are abundant and will last us for a long, long time So if we could use fusion to create our energy It would go a long way to solving all the world's energy problems So I'm going to tell you a bit more today about fusion About what it is and how we do it And also the machines, the tokamaks that we use to make fusion And hopefully through this you'll get an idea about How the physics that you learn at school relates to what scientists are doing every day And how we hope to make the power stations of the future So let's have a think about what fusion actually is And to start, I'm actually going to do a bit of a quiz Because we need to make sure that you know some of the basic atomic physics If we're going to be thinking about fusion So, hold on a second, haven't I said the question yet? So, this is the structure of the atom Okay Is the atomic nucleus made up of, is it protons and neutrons or is it electrons? Brilliant Hey, hey Okay, it's protons and neutrons So, this is the basic structure of the atom, this is helium You've got a nucleus in the centre This is made up of protons and neutrons And around the outside you have electrons, a sort of electron cloud That's basically what an atom looks like Now, what about the charge on a neutron? Is it negative, positive or no charge? C Quite conclusive, C there Okay, great, neutron has no charge Okay, so you've got the atom, we've got a nucleus at the centre Electrons around the outside But it's that whole atom, like how many times bigger is that whole atom Than just the nucleus at the centre You all think it's B? It's B That's great, it's a hundred thousand times bigger So, imagine for me that you're standing at the centre of a huge football stadium And you're holding a pin Now we're going to imagine increasing the size of the atom So that the nucleus is the size of that pin head So, you're in the centre of the stadium Nucleus is as big as the pin head So where are the electrons? They're probably about the back of the stands So going about 200 metres away The back of the stands And your nucleus is only the size of a pin head The electrons are even smaller And they're 200 metres away So the rest of the atom is all empty space, there's nothing there In fact, there's so much empty space in atoms And if you took all the space from all the human race The whole human race would fit into a sugar cube That's how much empty space there is in atoms But now, let's think about different types of elements So the type of atom depends on, is it how many protons are in the nucleus Or how many neutrons are in the nucleus A, B Bit mixed today A, I think the A's were winning there So, the type of atom depends on how many protons are in the nucleus Now, so these three pictures here, these are all different types of hydrogen They're called different isotopes of hydrogen They're all hydrogen, they've all got one proton But they've got different amounts of neutrons So this is what hydrogen normally looks like It's just got one proton and one electron around the outside Now, if we add another neutron, we've got deuterium It's heavy hydrogen, it's still hydrogen because it's only got one proton But it's got an extra neutron And then, this one here, this is tritium, this is even heavier Again, it's still hydrogen, one proton, but it's got two extra neutrons So these are different varieties of hydrogen Now, this is just a very big element, this is uranium So you can see how many protons and neutrons you can squash in to build up a really big nucleus Okay, what about the charge on a nucleus? Is the nucleus positively charged or is it negatively charged? A A, yes, it is, it's positively charged The nucleus is made up of protons, which are positively charged and neutrons, so the nucleus is positive And the two similar charges attract each other or repel each other B, yes, they repel each other So opposite charges attract, but like charges, will repel each other The fusion reaction that we use on Earth in Tochimax is actually different to what happens in the sun The sun starts with protons They fuse two protons together to make deuterium But that means that one of the protons has to turn into a neutron And that stage, turning one thing into another actually takes a long time, it takes millions of years Which is just as well really, because otherwise the sun would have burnt out long ago and we wouldn't even be here But if you're trying to make a fusion power station on Earth you don't really want to wait millions of years So we need to do something a bit faster So we start with bigger building blocks We start with the isotopes of hydrogen, deuterium and tritium And what we do is we combine the deuterium and the tritium And when they come together, their nucleons, the protons and neutrons all rearrange themselves And out of that rearrangement we get helium with two protons and two neutrons and we have a spare neutron So that's the main fusion reaction that we use on Earth in Tochimax Deuterium plus tritium gives helium and a neutron But now looking at this and thinking about what we've just been talking about in the quiz Can anybody tell me what kind of problem or what kind of difficulty we might have in getting this reaction to happen? Anyone? When you just be empty space, saying empty space and what's the chance that the things are going to hit each other? Well, you're right, it is quite difficult because they are very small But every now and then they do hit each other But there's something that's sort of stopping them from hitting each other It makes it very difficult to get them together, there's somebody here Is it the two protons that are repelling each other? They repel each other, exactly The two nuclei are both positively charged So they repel each other, they don't want to come together And so for that reason we do need a lot of energy in order to get them to come together So what are we going to do? Well, we give them a lot more energy So we heat our gas up to 100 million degrees That's hotter than the centre of the sun So we get the particles moving really, really quickly So that if they do collide, they're going so fast that they slam into each other really hard Hard enough that they can get close enough to fuse And now if we heat the gas to these kind of temperatures to hotter than the centre of the sun Then we have what's called a plasma So we don't have a gas anymore, we have a plasma So that's a special kind of gas It's a charged gas, or it's the fourth state of matter So you know about the states of matter You know that you have solids, you have liquids You have gases, and now you have plasma So if we think about a solid, first of all In a solid, the particles have fixed positions They've got a bit of energy, so they do vibrate a little bit But their positions are fixed, and you've got a solid Now if we give them some energy, so if we heat them up a bit Then we move the particles around a little bit more They're moving faster and they're able to break away from their fixed positions, and the substance can flow And now if you give them even more energy The particles are going to start moving around even faster Some of them are going to have enough energy to escape from the surface of the liquid and become a gas And so if we keep heating Then we're going to make the whole liquid a gas It will take up the whole container or the whole room And now if you keep on heating, so if you give them even more energy Then what you're able to do is actually strip the electrons away from the central nucleus of the atom And so then you have the negative electrons out on their own And the positively charged nuclei moving around on their own So then we have a charged gas or a plasma So you can see in the pictures up here This is just like a gas, but it's got separate Charges, it's got two things, the electrons and the nuclei So that's a plasma And because the plasma is charged, it has free charges in it It can conduct electricity And that's what makes plasmas quite special So, in order to show you some plasmas and show how they conduct electricity I'd like a volunteer please to come and help with a demonstration Yes, you can come up, thank you Just come and stand around here, I'm going to go around the back Can you turn the lights down please? Thank you Right, just touch it with one finger and just sort of drag it around a bit Okay, so this is a plasma ball And what's happening in here is you've got gas inside this sphere And electricity, so current, is coming up into the middle And the only way to get out to the edges of the ball Is to strip away some of the electrons from the atoms in the gas So to make a plasma And if they make a plasma, then those electrons carry the current So that's what you're seeing here You're seeing the current going from the centre of the ball Out to the outside, by making a plasma And now I've also got this tube, this is a fluorescent tube Like you might find in the lights in your kitchen Or your classrooms, do you want to hold that? And just touch the other end to the... So this is another kind of plasma, again Again, inside this tube you've got gas In order for the current to flow, it has to make a plasma And conduct the electricity along the tube If you hold it in the middle, you'll see that... Just take the other hand off, there you go So it should only light up up to your hand Thank you very much Give me a round of applause And now plasmas, plasmas are actually all around us In fact, you're more familiar with plasmas than you think Because, well, these are plasmas Neon lights are also plasmas Flames are plasmas, the sun, the aurora, lightning All of these things are plasmas So you're really very familiar with them And now I'm going to demonstrate making a plasma with a high voltage There we go, can we have the lights down again, please? This is like a mixture between lightning and flames So again, in order to get a current travelling Across the gap, it has to make a plasma It has to strip electrons away from the atoms So that the current can flow, and it makes a plasma So those are both demonstrations of different types of plasma But now, if we've got something that's hotter than the centre of the sun How are we going to contain it? What are we going to do? What we do is we use a magnetic field Because it turns out that charged particles in a magnetic field Feel a force, so we can trap them In these pictures here, if you look at the top picture That's like there's a plasma in there but there's no magnetic field And the particles just move around completely at random If you put a magnetic field in Then the particles actually generate a spin around the magnetic field lines So they all line up and they're all trapped And so this is what we can use to trap particles And this is just, this is just circular motion So it's just as if you have a tennis ball or a conqueror Or something on a string that you're swirling around The reason that this tennis ball keeps going round in a circle And doesn't fly off in a straight line Is that there's a tension force along this string And that pulls it around So that it pulls it around incrementally and stops it from flying off And that's exactly what happens to a charged particle in a magnetic field The charged particle is like this ball And as it moves it feels a force exactly as if it's attached To the magnetic field by a string And so the charged particle spins round And it's held orbiting around the magnetic field line And that's how we can use magnetic fields to trap plasma And magnetic fields can be quite powerful So they can be quite useful to us And to give you an idea of how powerful they can be I'm going to do another demonstration This time it's about electromagnetic induction An electromagnetic induction was actually discovered by Faraday In about 1831 in this very building Which is quite exciting So I think it's quite exciting So I need two volunteers to come and help me with my demonstration I can't see, can I see? Yes, okay, you can come out Can you just come around here and stand behind one of these pieces of carpet And I'm going to give you a tube each Right, thank you You can have a magnet as well So what we're going to do is I've got two tubes here A metal one and a plastic one and two strong magnets And we're going to drop the magnets down the tube at the same time And have a bit of a race, we're going to see who wins, okay? Do you want to take this magnet? So try and hold them above the carpet, thank you Okay, ready, go Okay, that one's there, the magnet's dropped But where's yours? There we go, this one took a lot longer to fall Did you see that? It took much longer, do you want to have a look down the tube and tell me what it looks like? Try and keep the tube straight Instead of going in circles It sort of looks a bit like it's floating, doesn't it? Yeah, it looks a bit like it's floating or going in slow motion So anyway, something here is slowing this magnet down Does anyone have any idea what it could be? Yes? It's like orbiting around the tennis ball Not exactly, but there's something different about these two tubes Do you know what's different about these two tubes? Yeah? That one's magnetic and this one isn't? Well, this one's not actually magnetic, so it's metal, but it's not magnetic So it doesn't stick to it, but there's something else different So it is to do with the fact that one is metal and one is plastic But does the other one, what does metal do that plastic can't? Metal conducts electricity Exactly, metal conducts electricity So there's something going on here that involves electricity And this is electromagnetic induction So because charged particles feel a force due to magnetic fields This changing magnetic field as the magnet drops actually generates a current that flows around inside this tube And then that current induces a force that pushes back up on the magnet and slows it down But that's why you only see it in the metal tube and not in the plastic tube Because the plastic tube can't conduct electricity Thank you very much, can you give them a round of applause, please? Thanks So yeah, electromagnetic induction and magnetic fields are very useful because we can use them to trap our particles And we use them in machines which are called tokamaks Now you might be wondering where the word tokamak comes from It's actually a Russian acronym It stands for toroidal nyacamera magnitnyakitushka Which is a bit of a mouthful Toroidal nyacamera magnitnyakitushka It means toroidal chamber magnetic coils And that's exactly what a tokamak is So what we have here is a torus So a doughnut shaped vessel with magnetic coils that make the trap for the plasma And it started off with coils, a coil of wire like a solenoid And then a magnetic field will go through the centre of the solenoid like this But you can see that if you trap charged particles that way they'll spin around the field lines, they'll stay away from the edge but they'll escape out the ends So that's not much use, so what they did was they wrapped the solenoid back round on itself to make a doughnut shape And then the magnetic field now goes around inside the doughnut shape So the particles are trapped going round and round inside the ring And that's what you're seeing here in this picture The blue coils are the solenoid that's been wrapped round on itself and the plasma particles move around on the inside But it does get a bit more complicated than that Because we actually have to have another magnetic field so that in combination the particles travel in a sort of spiral a helical shape around the doughnut because we find that that gets them trapped much better And then also you can use the magnetic fields to shape the plasma So you can stretch it out or squash it up or make it into a D shape You can really change it around with the magnetic fields And you can also use the magnetic fields to move the plasma push it around in the vessel So it does get more complicated and on top of that we do things like heat the plasma So there are extra bits on the outside to heat it And we want to look at the plasma, so we have diagnostics there called so that we can find out what the temperature of the plasma is or the density So there are all these extra add-ons around the outside of the tokamak And that's why the video that you saw at the beginning looked quite complicated So there's lots more added on to this picture And tokamaks come in many different shapes and sizes and they're all around the world So fusion is really a worldwide collaboration More than half the world are working to make fusion a reality And now this is jet, this is a joint European tourist So this is what you saw, the machine that you saw in the video earlier on And jet's the biggest tokamak in the world It's an Oxford ship And yeah, we've done fusion on jet We've made real fusion reactions in this machine Now this picture shows the inside of the donut-shaped vessel, the tourist That's what it looks like when it's empty But on the right, this is a picture of one of the experiments on jet And what might look a bit strange is that it looks like there's nothing there in the centre where you'd expect all the plasma to be It's just empty Well, it's not really, there is plasma there Most of the plasma is right in the centre The thing is, it's so hot that you can't see it It's so hot that it emits light only in the ultraviolet or the x-ray part of the spectrum So we can't see it, all we can see is the cool stuff around the edges Because in the centre, the plasma is about 100 million degrees But it cools as it goes out And so by the time it gets to the edge, it's more like a few thousand degrees And now this is a video of a plasma on jet So that's the real video of one of the experiments that has been done on jet And now if we're going to talk about jet, we should also talk about robots Because jet's been pioneering the use of robots for many years now And the reason that we'll need robots in a fusion power station is because of radioactivity Now I said earlier that fusion doesn't produce any long-lived radioactive waste And that's true, the products of the fusion reaction are helium and a neutron And helium is safe, so it doesn't produce any radioactive products But the neutrons have a lot of energy They move very, very quickly and also they fly out of the machine and through the walls And when they do this, they can actually bash atoms out of the walls of the machine And they change the properties of the materials when they do that And part of this is that they make the structure slightly radioactive So that means that over time, as the vessel becomes more and more radioactive Humans won't be able to go in there to make repairs They're going to have to send robots in to do it And the robots that we use on jet are kind of similar to these toy snakes that you might have seen or played with when you were children And the reason that we use robots that look like these snakes is because they're made up of lots of little joints And these joints give a great flexibility of movement It means that they can go through a very narrow porthole And they can bend round the whole doughnut shape of the torus to make repairs And this is an animation of the robots on jet And now the work that the robots have to do can be quite fiddly They need to do things like unscrew screws and move tiles around So people who operate these robots are going to have to be very accurate They need to have a lot of practice And so this is a video of somebody practicing operating the robot And he's playing Jenga Now it's a big full-sized Jenga, but it's pretty difficult So why does fusion release energy? Now this is all due to something called binding energy Which is the energy that's required to split an atom apart And so when the nucleus comes back together, it will release that energy Now I like to think about it a bit like an elastic band Because if you've got an elastic band and you stretch it Then you're having to put in energy to do that But then if I release it, I'm releasing all that energy So when the band comes back together, it's releasing it And that's exactly what happens in the nucleus So if you're pulling the nucleus apart, it takes energy But when the nucleus comes back together, it releases that energy And now this curve, this binding energy curve Shows us why fusion and nuclear fission will release energy Because binding energy is increasing up here And everything's getting heavier The elements are getting heavier along this way So hydrogen is down there at the bottom And then everything gets heavier Up here you've got uranium, the very heavy one So now every time you're making anything You're going from something with a lower binding energy To something with a higher binding energy Then you're releasing extra energy So any time you're going up this curve You're releasing energy So nuclear fission, which is the splitting apart of big, heavy elements So uranium here will split apart into two smaller products Maybe around there They're releasing energy because they're releasing all this energy As it goes up the curve And in the case of fusion, you're starting with hydrogen Down here And you're fusing those together to make helium Which is right up here So now you're releasing all this energy So fusion releases more energy than fission even And you can also think about it In terms of something called missing mass Now it's a bit weird But if you weigh the deuterium and the tritium that you start with And then you weigh the helium and the neutron at the end The deuterium and the tritium weigh more Which is a bit strange because it means that During the reaction, we've actually lost some mass Some mass has disappeared And it was Einstein who said that energy and mass are equivalent So they can be transformed into one another And you've probably all heard his famous equation E equals mc squared Well here they're saying that the energy E is equal to the mass, the change in mass Times the speed of light squared And the speed of light, c, is a really big number It's about 300,000 kilometers per second So c squared is huge And that means that you only need a tiny, tiny change in mass And you can get a huge amount of energy out And that's why fusion releases so much energy Because you're breaking nuclear bonds Rather than just chemical bonds when you burn a fossil fuel So that's why fusion releases so much energy And you'll remember that we said earlier That just one kilogram of fusion fuel Releases the same amount of energy as 10 million kilograms Of fossil fuels So it has a huge energy potential But now how do we get the energy out to make electricity? Well you remember the fusion reaction, you take Deuterium and tritium And out of it you get helium And you get a neutron as well Now this neutron is able to escape the magnetic trap And fly straight out of the machine Can anybody tell me why the neutron can escape the magnetic trap? Because it doesn't have a charge? Exactly, a neutron doesn't have a charge It's not trapped by the magnetic field Because a magnetic field only traps charged particles So the neutron can come straight out And also the neutron carries away most of the energy of the reaction And this is due to something called the conservation of momentum And so I'd like to have another volunteer please to help me with a demonstration Anybody over here? Can't see anyone? Okay, yes, you can come out Thanks Sorry, I can't see anything up there Hello Okay, do you want to hold this for me? Great Now what I'd like you to do is just drop it on the floor Don't throw it, just drop it It's not very bouncy, is it? Now instead, do you want to stand sort of here so these guys can see? Just hold it like this, hold them both, the top ball as well And just drop them together like that That was a lot bouncy, wasn't it? Great, do you want to do it again? Try it again Careful where you aim it Brilliant, thank you So what's happening here is that When we drop these balls, they fall together They collide with each other And when they collide, they each transfer a bit of their momentum to the other one But this ball is much bigger and heavier So it has a lot more momentum So it transfers a lot more to the little ball It gives it a bit of a kick And then this little ball, because it's very small and light It can move away quite fast So it escapes quite quickly So if you do it one more time, I think they'll probably give you a big round of applause Brilliant, thank you So that's why the neutron, the small particle in the reaction Takes away most of the energy And this is the basic diagram of how we will get the energy from the fusion reaction into electricity So around the edge of the donut shape, you'd have a layer, a blanket layer of lithium And now the lithium does two things First thing it does is it reacts with the neutron to form tritium And tritium is one of the fuels So this can just be pumped straight back in to the machine The other thing it does is it heats up And so this blanket heats up And we can use that heat to make steam, drive turbines and make electricity In exactly the same way as we already do in power stations So that's how we get the energy of the fusion reaction out into electricity But also, while we're talking about a lithium blanket It's a good time to talk about the fuels for the reaction Because although we need deuterium and tritium for the fusion reaction The fuels that we will actually need for a power station are deuterium and lithium Because the tritium will actually be made inside the machine And so deuterium is found in water So there's plenty of that around And lithium is found in the Earth's crust and also in seawater So again, we've got plenty of that So the fuels will actually last us for tens, if not hundreds of thousands of years So we're never going to run out of fuels There are still some challenges on the way to commercial fusion power One of the main ones is that we need to get more energy out of the reaction than we put in Now that sounds quite fundamental if you're building a power station But we haven't done that yet We've made real fusion reactions on jet We have done that, but we haven't got more energy out We've only got about 65% of the energy out of the reaction That's what we put in to get it in the first place So we need to do better than that Q equals 1 is the break-even point We want to get above break-even We want to get more energy out than we put in And the next big machine that's being built in France at the moment, Eta Eta plans to get more than 10 times as much energy out of the reaction as we put in And also jet is currently being upgraded at the moment So it's getting a new wall put in And they're hoping that once this is done It will perform better and break some of its records And maybe even get past break-even So it could be in the next few years even that we get past break-even After that, the biggest challenges now are actually material science and engineering Because you've got to think about how you're going to build a power station So if you can do the fusion bit in the middle You need to think about how you're going to build it And this is a really challenging thing because if you think about it You've got high temperatures, you've got high currents, high magnetic fields High energy neutrons flying out of the machine As I mentioned earlier, the neutrons that come out Can actually bash atoms out of the walls of the machine and they change the properties They make it more brittle, they make it more prone to damage And if you're building a power station You want to build something that's going to last for say 40 or 50 years You don't have to keep replacing bits So that's a challenge now for material scientists to find Materials that can withstand the high energy neutrons Or for the engineers to design machines carefully So that they can withstand forces that are created But also if they need to replace bits They want to be able to design machines so that we can replace things quickly, easily and cheaply To minimise shutdown times Another thing that we're looking into is something called disruption mitigation And disruptions is what I work in So these are some pictures from my experiments A disruption is when the plasma dies effectively So when the plasma loses all of its energy And sometimes you lose control of the plasma and it hits the wall And this is what I study, so in these pictures here This one here on the left is what we want a plasma to look like normally So nice and central inside the machine On the right, this is when we've lost control of the plasma And here it's actually moved so much that it's hitting the ceiling So here this is the bottom of the plasma It's moved right up in the vessel, up to the top And you can see all the energy or the light that's produced When the plasma hits the ceiling And then when that happens Currents can flow from the plasma into the walls of the machine And then these currents can generate big forces Just like we saw when we dropped the magnet down the tube And these big forces can twist the machine or make it jump And so they can be potentially damaging So people like me study why these things occur With the hope of minimising them But the engineers also think about how to design the machine To withstand these kind of forces So these are the kind of things that are going on On the run-up to making commercial fusion power So there are challenges, but they're not insurmountable We kind of know what needs to be done in order to get there Although there is still work to be done Also you need to think about things like How do you make the best lithium blanket To get the most heat energy out And how do you get the helium out of the machine that you make These are all things that are going to be worked on So there's lots of interesting research That's going to be going on in the next few years And even the next few decades to make fusion a reality So now in summary, fusion aims to create a clean, green, safe And abundant source of energy for the future And the fuels are plentiful And they'll last us for thousands of years So fusion's a really exciting goal And it's your generation that's going to be Probably using the fusion power And maybe even contributing to making it happen Because you have to remember that it's new people And new thinking and new ideas that make technology progress And so it could be your ideas that make a difference So if you want to find out any more information Then you can have a look on my website It's melaniewindridge.co.uk And there are links on there to places like The Cullum Centre for Fusion Energy Which is where the big machine, Jet, is So if you go onto their website You can find out more about the machines that we use The Tokamax and research around the world into fusion So do go and have a look Thank you very much I hope you've got some interesting questions You said I was eco-friendly But surely about the, like, nuclear waste Or what was it? About the nuclear waste So I said that it doesn't produce any long-lived radioactive waste Which it doesn't The products are helium And the helium is safe So that's fine But yes, the machine itself does become radioactive Over its lifetime Because of these high-energy neutrons But this radioactivity isn't long-lived So it will not last a long time It will probably last about between 50 and 100 years After that time, it will be, well, less dangerous Than the waste you get from a coal-fired power station How long do you think that it would actually take For nuclear fusion to be actually A competitive energy protection scheme? Probably, hopefully we'll see it in about the 2040s I'd say, so a while yet There's still quite a lot that needs to be done So the next machine, Eta, will be researching Some of the things I was talking about in the challenges Trying to get more energy out than in Looking at what we're going to make the walls out of Looking at how you get helium out of the machine The best designs for the lithium layer All of those kind of things We need answers to those questions After that, we will build what's called demo So demonstration power plant And then that will check things like Getting the electricity to the grid And all the things the power station needs to do After that, we will build Then you'll be able to build commercial fusion power stations So even if you sped things up a bit We still need to answer those questions So there's still be decade or two Of research going into it But if you tried to build say A demonstration power plant sooner Or built more rather than just one big experiment Then you'd actually be able to make quicker progress It's not really renewable though Because to get it up to that temperature Like a million degrees You need to use electricity that's been made With fossil fuels And to maintain it and keep it going Yeah, no, it's not renewable at all But yes, you're right To get it going You need to put energy in We need to try and get more energy out Than we put in So the idea is to get to a stage Where the fusion reactions are going So you're creating the fusion reactions You create helium and you create a neutron The neutron comes out of the machine And we use that to make electricity But the helium stays in the machine Until we extract it But at least initially it stays in And it gives its energy to the plasma So it will actually keep heating the plasma So once you get it going It sustains itself So you don't have to keep heating it So yes, you do need some electricity to get it going But once you get the fusion reactions Working They will actually keep the plasma heated Are there any other disadvantages That we don't know about Apart from the radioactivity The 50 years or whatever radioactivity Secret things I haven't told you No, actually, I've told you most of it The biggest disadvantage with fusion At the moment is that we can't do it That's the biggest issue But as I said, we're working on that And also, yes The fact that it does become radioactive Is a shame It's a problem, but again We're working on that as well And we're hoping to be able to minimize the radioactivity And even if we can't Like I said, it's not It's not as big a deal as having Long-lived radioactive waste that you have to bury We would really be able to just Leave it aside for a while And then after 50 to 100 years We'd be able to recycle it So that's probably the biggest disadvantage That and the fact that we can't do it yet And it is very difficult What would happen if the energy Came out Of the actual Takamaka or whatever So What would happen if the energy Came out of the machine Do you mean like Could it be dangerous? If it breaks down, what would happen? The good thing about fusion Is that it's really quite safe Because like I was showing the pictures Before of the disruptions with the plasma hitting the wall If the plasma hits the wall It's okay It doesn't explode or do anything like that It actually just cools down And if it cools down Then you just have a load of gas in your machine Doing nothing So it's not dangerous in that way It's not particularly good for the machine Because as I said You get big forces generated But it's not dangerous So the energy itself Doesn't really just like Come out of the machine like that In fact there's not really very much stuff In the machine at all In that big Takamaka Silver Donut Shake Vessel Inside that All there is is about the weight Of a postage dump of gas There's hardly anything in there at all You know you said that efficiency was like 60% So what if it doesn't increase Are you just going to leave the machine or carry on? So what if we can't beat What we've got already That's an interesting question I don't think I get to choose The outcome of that But I think we just got to hope at the moment That it will increase There's data that goes back to smaller machines Getting bigger and bigger and bigger So like scaling up from that We have reason to believe that That the bigger machine Will be able to give us a better trap And that's partly A lot of it is due to the fact that it's just What you've got is you've got a plasma And in the very centre You've got a very very hot 100 million degrees And All of this stuff Wants to get out It's a bit like if you have a pan of water On the stove And it's bubbling away and the hot stuff Is moving out and the cold stuff is moving in It's a bit like that So the hot stuff in the centre Is always trying to move out To the edges of the machine And so just by making it bigger You actually make it harder for the hot stuff To get out in the first place Which means you've got more time For fusion reactions to start going The machine will enable us to get more energy out And then In answer to your question We really hope and really think That we will be able to get more energy out Of the reaction that we put in I suppose if they couldn't do it At some point they'd have to give up But I'm not going to be the one to make that choice Thankfully Thank you