How a Fusion Reactor Would Work

And that's when you have a heavy atom that splits into smaller atoms after some sort of process such as absorbing and incoming neutron, and as a result, it releases energy as a byproduct. That energy can then be used to heat up water into steam and drive a steam turbine to generate electricity. So listen to the last episode for a full rundown of that. But now we're gonna

turn our focus to fusion. Now, with fusion, two or more lighter atoms are fused together to form a heavier atom, and they release a lot of energy in the process, more energy than you would get from a fission reaction. And rather than relying on heavy radioactive isotopes like uranium two thirty five or plutonium two nine, is fuel you would be using really light atoms that aren't themselves necessarily radioactive,

But doing so isn't as easy as it sounds. Fusion is the process through which stars emit energy, like stars in the galaxy, not on Hollywood Boulevard. The Sun is basically an enormous fusion reactor, and the Sun is massive. How massive you might ask, Well, if you look at our solar system, and if you add up all the mass represented inside that solar system, the Sun would account for nine nine point eight six per cent of all

of that mass. All of the planets, moons, asteroids, and other material would make up less than one per cent of the mass of the solar system. One million earths could fit inside the Sun. The Sun has a diameter of one million, six four kilometers or more than eight hundred sixty seven thousand miles, and most of the sun, like sevent of it, is made out of hydrogen. Most of the remaining mass is helium, and the process of

fusion inside the Sun's core turns hydrogen into helium. It fuses hydrogen together and forms helium as a result at a temperature of millions of degrees. According to the song why does the sun shine which was made popular by They Might Be Giants. However, I should point out that song also has some inaccuracies, as we would no longer say the Sun is a mass of incandescent gas, which

is why they Might be Giants. Eventually revised the song with an updated verse and called why does the Sun really shine and says the sun is a miasma of incandescent plasma. But let's move on to understand solar fusion, we need to know how stars form. And yes, then this actually ends up being really important because it illustrates the parameters necessary to make fusion work. So before you have a star, you've got clouds of dust and gas out in space, just floating around in the same general area.

Then you get some sort of gravity disturbance, which could be caused by any number of things, such as a supernova. This ends up causing some of that gas and dust to clump together, and the particles are starting to move closer and closer in with each other. And as all this mass moves closer together, the force of gravity begins

to pull them in more tightly. You know, gravity depends upon mass and distance, so as this mass gets concentrated, it starts to create a gravitational pull gas it's drawn inward into the core of this mass, and as the pressure increases from the gravity pulling things inward, the mass begins to heat up and the clump then begins to rotate.

This heat starts to move stuff around, and there's rotation in the universe anyway, so you get some rotation of the mass of stuff, and this starts to flatten out into a disc. That process actually draws in more dust and gas that gets drawn inward and the mass continues to heat up. Now skip ahead about a million years.

You've done a million years of this process where this disc has continuously been sucking up more dust and gas through gravitational pull and heating up over and over more and more, and the core of the disc has become a dense structure that we would call a proto star. Now, proto stars can turn into full blown stars, or they might not. It depends all on how much matter is around,

how much mass can they accumulate. So if there's enough mass in the form of gas and dust, the protostar will pull it inward heat up even more, and once the temperature hits around seven million degrees kelvin which is equal to about twelve point six million fahrenheit or nearly

seven million celsius. Fusion will begin. Hydrogen atoms will be stripped of their electrons because they have far too much energy, and the intense temperature and pressure will cause them to fuse together to form helium atoms, and that process releases energy. The nuclear fusion creates a strong outward pressure, so if there were no other boundaries on this system, the protostar

would just expand to the point where it dissipates. However, there's still that incredible gravitational pull that counteracts the expansion from nuclear fusion, and the young star will still pull in more material. If the protostar collects a sufficient amount of mass, the temperature will remain hot enough to sustain fusion, and the protostar will release a jet of gas called a bipolar flow. That flow will push away gas and

dust from the star. Some of that stuff could potentially clump together to form stuff like planets and moons, But if the protostar doesn't accumulate enough mass, the protostar will not become a fully fledged star. Instead will turn into what is called a brown dwarf. So we see that fusion occurs under intense temperatures and intense pressures. The same is true if we want to create fusion on Earth. So what is actually going on with a fusion reaction?

I mean, I know that we take two atoms of hydrogen and we push them together real hard in a very high temperature, high pressure environment, and we get helium. But how does that release energy, especially after you need so much inergy to make it happen in the first place. Well, I'm going to give a very simplistic answer to this, but please know that in reality, the real answer, if

you really boil it down, it's ridiculously complicated. So this is a very high level look at what is going on, But to go into more detail would require a very deep understanding nuclear physics. I frankly do not possess a deep understanding of nuclear physics. I have a cursory understanding, but I can sort of explain from a very very general level. So fusion involves binding those two lighter atoms

to make a heavier atom. So let's say we've got atoms number one and atom number two, and we combine them together and we get atom number three. However, we see that atom number three's mass is not the same as if we added up the mass of atoms one and two together. Right, So if we said that the mass of atom one is one and the massive atom two is one, the massive atom three might actually end up being one point eight, but not too so how is that possible? After all, matter, just like energy, cannot

be created or destroyed. Ah, but you can convert it. And this is where a real Einstein comes into play. His name was Einstein. Einstein's famous equation E equals mc squared tells us that if you were to convert mass into energy, the amount of energy you would get would be you take you take a mass, and you multiply that times the speed of light squared. And the speed of light is a really big number, like a huge number, and then you've just gone and squared it. You multiplied

that huge number by itself. Then you take that even bigger number and multiply that by however much stuff you have the mass of the stuff, and that tells you how much energy would be produced. It is an enormous amount of energy represented in a very tiny amount of mass. So the missing mass from this fusion process isn't really missing, it's converted from mass to energy, and that is why fusion reactions are so powerful. The amount of mass lost in the fusion process is tiny, but even so that

generates an enormous amount of energy. Now, like I said, there's an overly simple way of describing what is going on. We can get into quantum mechanics, we can get into nuclear physics, and I would be totally lost. And so there are a lot of details that I am glossing over, but at least gives a hint as to why fusion power is so tantalizing because it could potentially produce so much energy we could put to use in doing things

like creating electricity. But there are other reasons why fusion is really attractive as well, and I'll go into those in just a moment, but first let's take a quick break to thank our sponsor. So here's the idea for a nuclear fusion reactor. You would start with some isotopes of hydrogen. Now I mentioned isotopes in the previous episode, but just to catch you up in case you haven't heard it, isotopes are whord we use to describe atoms of the same element, but those atoms have different number

of neutrons from each other. The number of protons has to remain the same for these atoms, because otherwise you would have a totally different element. But neutrons have a neutral charge. They do not affect the chemical properties of the element, but they do change the atomic mass of the atoms. The two isotopes of hydrogen most frequently used for hydrogen fusion reactions are deuterium and tritium. Now first, before I talk about deuterium and tritium, let me talk

about protium. That's hydrogen one. That's the most common isotope of hydrogen. It consists of a single proton and an electron, no neutrons, and protium makes up about nine of all the hydrogen and found on Earth. Most of that hydrogen, by the way, is locked in with other stuff, hydrocarbons in particular. Then you have deuterium. Deuterium has one proton and one neutron in the nucleus, and it has one electron orbiting the nucleus. So it's like protium, excepted has

a neutron. So some of the hydrogen in the water on Earth is deuterium. Like one atom out of every six thousand, five hundred hydrogen atoms or so, then you have tritium that is hydrogen three. It has one proton, two neutrons, and one electron. Now, tritium can occur in very trace amounts on Earth in the atmosphere, but it

is exceedingly rare. It's typically only found in the tiniest amounts in the atmosphere after hydrogen atoms have interacted with cosmic rays, so there's no easy way of getting hold of it. But we can tots make tritium ourselves. That does involve irradiating other stuff, so I don't recommend taking it on as a d I Y project. Also, tritium itself is radioactive. It has a half life of about ten years, so tritium, while while deuterium is not radioactive,

tritium is. Fusion reactors would probably have to rely upon deuterium tritium reactions, which would create a helium four atom and a neutron. Now, if we could manage deuterium deuterium reactions just fusing to deuterium atoms together, that would be for the best because that would produce a helium three isotope plus a neutron, and the results would be preferable to the deuterium tritium. Because deuterium occurs naturally on Earth means we don't have to make it. We can actually

harvest it from the oceans if we wanted to. Plus, deuterium isn't radioactive, tritium is, and the reaction would yield more energy than a deuterium tritium reaction. But on the downs side, the amount of energy we would need to initiate a deuterium deuterium reaction is so great that it is prohibitive right now and possibly always will be. We just don't have the capability of creating that. Helium four, by the way, UH consists of two protons and two neutrons.

Helium three is an isotope that only has one neutron with those two protons. So where's the problem. We know what's happening with fusion, but why can't we make it a reliable reactor? Why can't we make a fusion reactor right now that produces more energy than it requires to operate? Now, first you have to create the conditions that allow fusion

to happen in the first place. Fusing nuclei together means you have to overcome the repulsive force you encounter when you try to smush together two particles with the same charge, and by repulsive, I don't mean they're disgusting. I mean

they repel each other. Like if you take two magnets and you try and put the north end of each magnet next to each other, you'll feel them resist that, they'll push against each other because like charge repels, like opposite charges attract, So a positively charged particle will attract a negatively charged one, but the same charge repels and to positively charged particles like protons, are going to resist

getting smushed together. They repel one another. You have to overcome that tendency, so you have to heat up the hydrogen to millions of degrees kelvin. That amount of energy will strip the electrons away from the hydrogen atoms, turning the atoms into nuclei, which would make a protium just become a proton all by itself, but deuterium, you would have a proton and a neutron together, and hydrogen would

change from gas form into plasma. Plasma is the most plentiful form of matter in the universe, because again that's what stars are made of, and we've already established how massive stars can be keep in mind, the Sun is not the biggest kind of star we've ever seen, so it's the most plentiful stuff. It's essentially an ionized gas, meaning that has free roaming part of electrons and nuclei

inside of it. Now, to get hydrogen to those temperatures, to heat up hydrogen enough to turn it into a plasma, we use powerful technologies and typically we use stuff like lasers or microwaves and ion particles to heat up the material to a temperature high enough where we can actually turn it into plasma. Then we have to use some form of containment to push all of those nuclei together big time. We have to really squish them in so that they are within one time's tent to the negative

fifteen meters to fuse together. They had to be so darn close to each other. And we don't have the benefit of having an intense gravitational force like the Sun has because of it's so massive. The gravity that the Sun exerts is so strong that it that that condition is natural in the core of the Sun. We can't replicate that on Earth. We don't have the control of gravity, so we have to use something else, and we typically use stuff like magnetic fields or lasers or ion beams

in order to do that. I'll explain how in just a moment, but first let's take another quick break to thank our sponsor. All right, let's talk about magnetic confinement. That means we're using magnetic and electric fields to manipulate the plasma to squish it into a tiny mass, and it also heats it up in the process. The International Thermonuclear Experimental Reactor, or at least that's what was formerly known as also called it and France relies on that approach.

Actually these days they say that i t e R no longer stands International Thermonuclear Experimental Reactor. Instead they say it is a reference to the Latin phrase for the way, probably because the word thermonuclear sounds super scary. But this reactor, which is a research project meant to explore the possibilities of using magnetic confinement to produce fusion reactions that will release more energy than it requires to initiate, has was

called a tacomac. That's a specific kind of reactor has an arrangement of magnets that are sort of in the shape of a of a doughnut or or toroid. And this kind of reactor would first convert hydrogen gas into plasma using microwaves, electricity, and neutral particle beams, and then those superconducting magnets would create an extremely powerful magnetic field compressing the plasma, and because plasma has an electric charge,

it's going to respond to these magnetic fields. The amount of power needed to start the fusion process, according to it, will be about fifty megawatts, but the fusion process would produce five hundred megawatts, meaning the thermal output power should be ten times greater than the heating input power, so you get a tenfold return on your power investment. That sounds pretty sweet, but itder itself will not produce electricity, at least not first anyway, it's meant to be a

research facility for the design and testing of fusion technologies. Now, if it were a fusion power facility and it was beyond research and development, the thermal energy generated from the fusion reaction would be used again to heat water into steam and push steam turbines, just like a nuclear fission reactor or even a cold power plant does. But would be really really good at this because it would be producing so much energy you could heat up a lot

more water. You could drive more steam turbines than other forms of steam turbine generators, and so you can generate quite a bit of electricity from the amount of energy you are producing through these reactions. In addition, because we're pretty sure we're limited to do tterium tritium reactions, I turn would also serve as a test facility to look at the feasibility of creating tritium breeder reactors. So a breeder reactor creates the materials you need for a different

type of reaction. So the the reactor is in what is called a vacuum vessel, and that vacuum vessel will have lithium blankets lining the inside of it, and those blankets will actually absorb energy given off by this reactor during the fusion process, and as a result, when you bombard lithium with radioactive energy, essentially it produces tritium. So that way you can actually create part of the fuel you need for future reactions as a byproduct of this process,

and then you keep on going. But that's magnetic confinement. There's actually another way we could use to keep plasma confined so that fusion reactions can occur and that is called inertial confinement. That one uses ion beams or laser beams to confine and squeeze the plasma. The National Ignition Facility at Lawrence Livermore Laboratory in the United States uses that methodology, and the n i F reactor would use two different laser beams to focus on a single point.

And it's inside a chamber. You've got this big chamber called the whole rom h O H L R A U M is the spelling for that, and the chambers specifically designed for radiant energy. That chambers ten ms in diameter. It's pretty big. So what happens at the one focal point where all those lasers are aimed at. Well. At that point will set a tiny pellet of duteri um tritium and it's encased in a plastic cylinder. The one laser beams will pour one point eight million jewels of

power into this cylinder. This creates an enormous amount of heat. It also emits X rays as a result, and this will help convert that pellet into a plasma. The lasers

compress this plasma and fusion occurs. The fusion reaction will be over in less than in an instant like one millionth of a second, but that reaction should produce about fifty to one hundred times more energy than what was needed to initiate the reaction in the first place, so the return on energy would be incredible, much more than

the magnetic confinement which was ten times right. So a series of experiments eventually got the plasma to produce more energy than it required to initiate, but the project never reached full ignition. They never got to the point where they fully ignited the fuel, where you had full fusion. Are research is ongoing at the facility, but the early optimistic hopes that full ignition would be reached by late

obviously proved to be too ambitious. Now, one day it may prove to be an effective process to use as a way to generate the energy necessary to drive electrical generators, but a lot more work has to be done to

achieve goals and create a sustainable approach. A sustainable approach, by the way, if you think about that setup where you have a hund lasers focused on one little point, how do you make that something that you can continuously do so that you can keep generating energy and create electricity while you would have multiple pellets inside the chamber, and the lasers would focus on one after another and initiate fusion for each of those in order to generate

the energy did to create electricity, So we got a long way to go. And like Eider, the n i F was not intended to be a power plant itself. It was a research and testing ground still is a research and testing grounds for technology for various uh applications, not just nuclear power but also nuclear weapons. Research goes on there. Uh Now it might that research might one day make fusion reactors practical. A fusion reactor like the one in i F research could lead to would generate

electricity the same way the Eider based reactor would. In other words, it would be used to generate energy that would heat up water to turn into steam. So it all comes back down to steam turbines. Seems like almost all the major ways we generate electricity, with the exception of something like direct solar power, has some variation of this. While we haven't cracked the nut on fusion reactors, it

does remain a tantalizing goal. Deuterium is more plentiful than stuff like your name two thirty five and it's not radioactive. Tritium is radioactive, but we'd create that from energy given off during fusion reactions, and so we could have breeder reactors produced the fuel supply needed for various power plants, and the stuff we'd used to generate the tritium is lithium, and we are lousy with lithium. Is that is not

hard to get hold of at all. The amount of fuel we would need for fusion reactions in general is a fraction of what we would need for a fission

based nuclear power plants. So that's the other nice thing about is that you don't need as much stuff to generate the energy you want to generate, right, You don't have to go mining for uranium two thirty eight and then enriching that so that you have enough uranium two thirty five to have a sustainable nuclear reaction, and the amount of radiation produced by such reactors would be less than the natural background radiation we typically encounter in our

day to day lives, and that's a nice change from fission based nuclear reactors. There's also no combust bustion with a nuclear fusion plant. There's also no combust in with a fission nuclear power plant, at least not if everything is working properly, so you aren't burning stuff and you don't cause any pollution that way, And unlike fission reactors,

fusion reactors would not produce high level nuclear wastes. You would still have low level nuclear waste, and that's still something you have to be concerned about, but that in general is much easier to deal with than the high level stuff. That's the again, one of the big reasons why fission reactors get so much pushback is this high level radioactive waste. But we'll have to wait a while

to see if this all pans out. Itter is scheduled to start doing plasma experiments in twenty five, so we're still a few years off before we see if that experiment bears fruit. N i F has been on and off again with their fusion projects, largely due to funding issues, and it's hard to convince government agencies to fund exploratory research when you cannot be absolutely certain that it's going to work. It's tough to say, yes, this investment is

a risk. It might pay off in ways we can't even imagine, because we would be able to generate so much energy that we would easily meet our energy needs for the foreseeable future. But if it doesn't work, then we've spent all that money for you know, some lasers that that turn some deuterium tritium pellets into plasma, but not enough of it to make it make a difference.

It's not a great way to try and get money, unfortunately, because government agents tend to want results because eventually the government agents have to report to the people who vote for them. And if if you're a voter who's very concerned with where your money is going, you might not want to hear about a risky scientific proposition that may not pay off in the long run. I'm always for exploratory science, but it's easy for me to say, right, I get that I'm from a very privileged position when

it comes to that. Now, in my next episode, I'm going to tackle a very controversial topic, and that would be the concept of cold fusion. Cold fusion is a process that, if it works, means that you would have adams like deuterium fusing together at room temperature. You wouldn't need to have these elaborate setups to create such enormous amounts of pressure and heat in order for this to happen, and if in fact it does work, it would dramatically

transform our world. We wouldn't need facilities like itter or in i F because we would be able to do this, you know, in a lab and a nice, nice lab with maybe some radioactive shielding because occasionally it would produce gamma rays. But I'll talk about that more in the next episode. So continue down this nuclear pathway with me as we talk about cold fusion. In the next episode and then the episode after that, we'll take a closer look at what actually happened at sites like Three Mile Island,

Chernobyl and the Fukushima reactors. So join us for those. And if you have suggestions for future episodes of tech Stuff, maybe it's technology, maybe it's a person in tech, maybe it's a company, send me a message let me know what you would like me to talk about. The email address is tech Stuff at how stuff Works dot com, or drop me a line on Facebook or Twitter. The handle for both of those tech Stuff h s W. Don't forget to go to t public dot com slash

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