TechStuff Classic: How Nuclear Weapons Work

I feel it's an important one. Nuclear weapons are frequently part of a discussion about global events and global politics, and so I thought it would be useful to revisit this classic episode where we talk about exactly how these weapons work. So enjoy Today. We wanted to talk about a subject that is, uh it's pretty terrifying. We're talking about nuclear weapons. Yes, yes, nuclear, not nuclear. He was. I was teasing him about this before and he said

that I better not. I'm not gonna say nuclear. I mean other than just them. Um. Well, one of the reasons I wanted to uh to talk about this today is because it's been in the news a lot lately. Um. Of course, uh iran um is rumored or depending on whom you ask, more than rumored to be working on nuclear weapons program and um, you know that that's been a busy topic. I was about to say, a hot topic.

Let's not go there um lately, and I thought, well, you know, why don't we We've never really talked about, um, the technology that makes nuclear weapons possible. Um. And while I'm not particularly fond of things that cause death and destruction, uh, the the actual bombs themselves, how they make them work is kind of interesting, and it's it's important stuff. I mean, you know, there's a lot of there are a lot

of discussions about nuclear arms races. You know, we had a famous nuclear arms race between the Soviet Union and the United States during the Cold War, which uh started to look like things were going to to improve, where you know, both nations were starting to dismantle a lot of their nuclear weapon programs. But then you've got other countries like China and India and Pakistan and other countries that are that have either have a nuclear weapons program

or developing. North Korea is another good example. They either have a and a fully fledged out nuclear weapons program or they're working on it. And uh, it adds a lot of concern because these weapons potentially pack an enormous punch and it's the kind of weapon that you know, most weapons, you use them and then the uh, that immediate moment, the aftermath, that's that's all you're dealing with.

And the aftermath is generally, you know, not not uh, something that is perpetual, right, I mean, I mean, you might have to do some massive clean up or whatever, but that's it. Nuclear weapons are different, and that the aftermath can be as destructive or maybe not as destructive, but but destructive on their own beyond the initial blast.

And so plus plus it's possible that the uh, the effects of the nuclear blast can carry across the terrain to places that the US, as we'll find out in in our discussion, um that people may not necessarily have been planning on being affected. Yeah you might. You know, it's not just the immediate area. It's not a precision weapon and that Yeah, there's a precision blast area that you're that you can be pretty sure is going to be vaporized when you hit it, but then there's a

large area around that. Depending upon the climate and you know, the specific weather conditions at that time, it could affect neighboring countries, you know, essentially innocent bystandards to whatever. So let's get into this. Let's talk first about atoms. Yeah, I mean, you think about it that one of the fascinating things about this is that such a devastating reaction

can be caused by something as tiny as an atom. Yeah. Uh. And just so that we all have our little a little refresher course, even though I'm sure no one listening needs it. Your basic atom has a nucleus that is orbited by electrons. Now your electrons are you're negatively charged particles. Yes, your nucleus typically contains at least one proton. Actually it

has to otherwise it's not an atom. So the proton is a positively charged particle, and the protons positive charge in the electrons negative charge are attracted to one another. It's pretty powerful. Now, there can also be in that nucleus a a particle that carries no charge at all, a neutron which has no charge, and neutrons kind of act like glue for protons, because you know, you've got

this this nucleus that could have more than one proton. Well, the problem is that as similar charges repel one another. So if you have to possibly charged particles and try and put them close to each other, they're going to start repelling each other. Well, neutrons kind of act like a glue that that allows these protons to group together to form this nucleus. So, uh, if you've I'm getting out of here. No, no, don't No, it's all right. That's all right. Now you can change the number of

neutrons that are within an atom. And if you do that, uh, you know, atoms have typically they have a number of neutrons that you will naturally find within the atoms of that element. Uh. If you find something that's outside of that that either is gut either has more fewer neutrons, it's an isotope. So isotopes of atoms are atoms that contain a different number of neutrons than you would typically find them in nature. Plus, isotopes are a baseball team

in springfield. That's also true. Now this is not to be confused with ions. And ion is an atom that has either gained or lost in electron, and so it either has a positive charge or a negative charge because of that. So of course if it's gained an electron, then overall the atom has a negative charge if it's lost in electron and overall the atom has a positive charge.

So that's the difference between ions and isotopes. Now isotopes really that's what ends up being important in these nuclear weapons. It's it's sort of a key feature. Um. Another thing that's that's important to note is that for the most part, atoms are pretty stable. Yes, I mean, once you get them in their natural state, they're unlikely to change all that much. They don't uh, randomly shed electrons or the

things unless some force acts on them. They just sort of go along there about their business and stick to themselves, right, because if they were if they were unstable, they would very they would not necessarily very quickly. But if they were unstable, they would change to become more stable over time. That's what we call decay. So if you have an atom that is unstable, it will eventually change to a more stable form. And in the process of that, it's going to give up some energy, uh, and it can

give up energy and in multiple ways. There's actually three main types of radioactive decay, that's right. There's alpha decay, which is where you've got your nucleus and it it's going to kick out two protons and two neutrons bound together, which is also called an alpha particle. Then you've got beta decay. And this is where a neutron actually changes becomes a proton. Uh. Then the neutron or the proton, and the an electron and an anti anti neutrino are

all ejected together. That's the beta particle, or actually the ejected electron is the beta particles specifically UM. So, yeah, good all anti newtrinos I tell you they they go opposite the as the speed of light. So we talked about the whole new trinos whether or not they were going faster than the speed of light with a large

hadron collider. Right now, it looks like they didn't. Looks like that was all due to uh, some some issues with the measuring technology looking at the scoreboard today, right, which could change by the time this podcast gets out. So the third type is spontaneous fission. Now, vision is where you have a nucleus split into two pieces. It's um the opposite of fusion. Fusion is where two nucleuses come together and join. And both vision and fusion you

have a release of energy. Now for radioactive decay, we're specifically talking about fission, not fusion. So in this the nucleus splits and it might eject neutrons which can become neutron raise, and it also can emit electromagnetic energy called gamma raise, which do not talk about fantastic four. You're looking at me like I was talking about some or the Hulk. I was waiting for you to make that. Actually I think it was cosmic rays with the fantastic

gamma radiation for the incredible Hulk. I don't want to get my science wrong. You're absolutely scientific. My air quotes science wrong. So yeah, gamma raise. It's interesting that they are the only type of nuclear radiation that comes from energy rather than particles. Yes, all right, I bet you learned that on how stuff Works dot com. Yes, there's

a really good article about that. We we have. We have a couple of articles on how stuff Works dot Com that are going to be really useful as we talk about this, include how nuclear weapons work, how nuclear how nuclear radiation works, and also how there's an article about the Manhattan Project. We'll talk about the Manhattan Project in a little bit. So we've now got these three different forms of radioactive decay, and we know about this

new the spontaneous fission. Well, what's interesting is that the fission doesn't necessarily have to be spontaneous. If you find the right kind of unstable atom and you are able to bombard it with neutrons, then sometimes those atoms will accept a neutron and in the process they will become so unstable as that the nucleus itself will split apart,

and in that process the nucleus will release energy. It also may release other neutrons, which means that if you get a bunch of these unstable items together and you shoot a neutron at them, and then that first that first nucleus splits apart and more neutrons split off of it, it can cause more of these unstable atoms to do the same thing, and that's where you have a chain reaction.

I can't remember who it was that had that the TV show where they had a clear plastic box and on the bottom of the box they had uh mouse traps, and each mouse traps, each mouse trap had two ping pong balls on and those represented um the stable. Actually, it's probably been done by five thousand people. Anyway. You can find clips of the same sort of thing on YouTube and then by lots of different people, and I

enjoy watching it because it's really an excellent demonstration. So each of these these mouse trap atoms with its two ping pong balls represents these unstable atoms, and it's so and the ping pong balls represent the ejected neutrons exactly exactly, and so uh, somebody else will drop a ping pong ball inside a small hole in the box representing the neutron in this case that is bombarding these these atoms.

And as soon as it hits one mouse trap and sets it off, the pong balls from that one fly in other directions, thereby setting off the other mouse traps. And it all happens in a very very short period of time. It takes almost no time at all for this thing for all the the mouse traps to release their part of ping pong balls. Yeah. Now, and in the case of a nuclear weapon, these reactions are happening in billions of a second. So now let's get to

the actual elements that are used in nuclear weaponry. So one of them is an isotope of uranium, uranium two thirty five. That's a very complex atom. Yeah, it's got ninety two protons right, So, but it's got a hundreds forty three neutrons. And the thing about this is that it will accept a neutron. If if you bombard uranium two thirty five, it very easily will accept that neutron.

Take that neutron, yeah, and then it it makes the uranium unstable, and then it will split apart like I just said in and you'll get that energy and those other neutrons released. So that the problem the problem with this, many problems with this. One of the issues that the people who first started working on nuclear weapons technology encountered was that, first of all, they weren't sure which elements were going to react this way because not all of

them do, so finding the right elements was tricky. The other part is that uranium two thirty five is relatively rare compared to other isotopes of uranium. Yeah, so when you find naturally occurring uranium, the uranium two thirty five in that deposit is going to be relatively sparse, and for a nuclear weapon to work, you need about uranium two thirty five so that you have the right amount

of material to perpetuate this chain reaction. Otherwise, your your atoms that are unstable, maybe too far apart from each other for or that chine reaction to really take off. Note to all the nuclear physicists who are righting, who have paused to podcast and rode in to tell us that there are other types of fuel that can be used for nuclear weapons. Yes, we know that. However we're using we're starting here, starting with uranium because that's where

that's where, that's where the scientists started. Yes, plutonium also used, as well as their hydrogen bombs that we'll talk about a little bit. But even hydrogen bombs use uranium and plutonium um. It's just that they're they're using a different mechanism. They're using confusion as opposed to vision. So uranium two thirty five, you have to actually refine your your right,

your uranium. Wow, I can't talk today, but yes, you must take uranium your uranium, yeah, toy boat anyway, you have to take this uranium there we got that works and refine it so that you have a higher percentage of uranium two thirty five, which is what you hear about when you when you hear about these these nations like Iran with their nuclear program, you hear about are they making uranium for power facilities or are they trying

to make weaponized uranium. This is talking about the enrichment process. Yes, so if you are enriching, if you're if you're creating uranium so that you've got a section of ranim that is uranium that's indicative of a weapon, it's not. You don't need that kind of concentration for a nuclear power facility. So that's one of those things that that inspectors try to determine when they go and look at a nuclear power facility to make sure that the uranium being produced

is not weapons grade uranium. So anyway, that's the basis, that's the basic science behind the fission part of nuclear weapons. Will get into fusion in a second. So how did this all come about? Well, first we have to look at a fellow named Einstein. Now, Einstein came up with that famous equation E equals MC squared the theory of relativity, which states that energy is equal to mass times the speed of light squared the constant of the speed of

light through a vacuum. As it turns out, so that means that you take the you take a unit of mass, you multiply it by the square of the speed of light speed light squared rather and and then that's how much energy you get from that mass. So this tells us that a tiny little bit of mass could equate to an enormous amount of energy because you're multiplying that

that unit of mass against a huge number. Well, that starts leading people to think, well, this is true, then there should be some way to tap into the stuff that's around us and get at huge amounts of energy. And you had a lot of really really smart people working on this, and most of them were probably at least initially working on this is the way of finding

a new energy source, not necessarily a weapon. However, World War Two really helped push the the the the research towards finding a way of using this in a military application as opposed to to just a power generation alternative. So then we go up to the nineteen thirties. You've got a fellow named Enrico firm me and he support

on him in grade school. He's the one who discovered that if you were to shoot neutrons at atoms, you could sometimes form new elements, and they were including ones that just did not show up on the periodic table at all. So most of these are are atoms that are so unstable that you know, they almost immediately decay.

But uh that he discovered that. And then a few years later a pair of German scientists Otto Han and Fritz straw Sman discovered that by bombarding uranium with neutrons that they could create cause the uranium atoms to split.

So they're the ones who actually connected the concept of fission with shooting neutrons at an isotope and uh it actually created a radioactive barium isotope once they did that, and that's how they discovered, oh, you know, this is what happens if you do this, then you have a couple of other There are so many famous names that we could mention that worked on this, but Neil's Bore and John Wheeler started to theorize that if you were to create a fission reaction within enough of this material,

you could cause a chain reaction, and if you were to contain this in some way, you could have a controlled nuclear reaction which would generate huge amounts of energy. Uh. Now, a controlled nuclear reaction could allow you to have uh power, or a controlled nuclear reaction that then results in an un controlled explosion is a weapon, it's a bomb. You know, I'm sort of reminded of our our discussion of quantum computing,

which also works with Adams UM. But the thing is that figuring out the predict predictability if you happen to listen to that podcast of where the particle will go and in what direction UM is not always possible. That's one of the things that makes quantum cryptography so useful. But yeah, in this case, UM, it's kind of scary because if you imagine that this this reaction is going to unleash a large amount of power, or maybe it won't.

You know, that's that can be a little scary because you don't know for sure exactly what's gonna happen when you do this. Is which is why UM. You know, they started doing experiments like you know, Columbia University in UM up in New York. They starting to mess around with this to see if they can make it work. University of Chicago squash court. Yes, yes, now that's funny because of underground underneath the fame stag field there at the University of Chicago. UM they were Enrico Fermi finally

got it to work in controlled situation. UM. So you know, again, what what if it weren't controlled that might have been a little scary, but uh, you know, he got it to to to do what they thought. And this this was important because um again this is they realized that this could be a seriously potent weapon that they could be building. So um they realized that if they could harness this and do this in a controlled way, you know,

then they could turn it to their advantage. Um. Around the same time that work was being done on uranium uh and and nuclear fission, scientists over at the University of California at Berkeley back in one discovered a new element, element ninety four uh and they thought that this could also work as a potential fuel for nuclear chain reactions. And this element they named plutonium and named for the dog. Yes, it was named for the dog the it took it

took his name for the Roman god. But yeah, it was a year later they had actually produced enough plutonium to finally do some experiments on it, because it was not something that was easily found, which I guess we should all be thankful for. Um. And they they figured out that plutonium also would undergo fission when bombarded by neutrons.

You know, we should talk about the criticality of about the of the the atoms themselves, because the thing is um say, say you have your your creative mousetratched and ping pong balls. You have to make sure that nothing is going to set it off before you mean to set it off. Yeah, you don't want to have something jostle that that's some and have it all go off prematurely. And of course with a nuclear bomb, this is truly important because of the the just the enormous amount of

damage that it could it could, it could cause. We have more to say in this classic episode of tech stuff, but before we get into that, let's take a quick break to thank our sponsor. There's a couple different concepts here. There's a concept called critical mass, which is the minimum amount of mass necessary for you to have a sustain

nuclear fission reaction. And then there's the subcritical mass, which is where you've got lower than that amount, And ideally what you want is to have lower than that amount up until the point where you actually want to detonate the bomb. Yes, because that's going to keep it as

safe as you can you can get it. So there were a lot of challenges in trying to find a way to create a bomb where you had the material set up as subcritical until the moment of detonation where it would convert to a critical mass so that that nuclear reaction would remain sustained within it. Otherwise your bomb would still be dangerous. So it's still emit radiation. It was still a middle lot of energy. It just wouldn't cause as much damage as it was designed to do.

Right now, now, critical mass is, as Jonathan said, the minimum amount needed to to achieve the fish and reaction. Now. Uh, ideally for a for a bomb condition, if you're you're trying to do this, um, you would want the fuel to be in a supercritical mass, which basically means there's more than enough necessary to achieve the fish and reaction. Um uh you know, because in this case it just applies and plenty. You want to make sure that it's

going to happen. You don't wanna, you don't want to have it where through some weird set of circumstances, just some improbable but possible outcome that the bomb that as a smaller percentage of the reactions takes place than you had anticipated, because that means that the effect is going to be smaller than you had anticipated. And if you're gonna be building something as nasty and dangerous as a nuclear weapon, you kind of want it to be effective. Yes, Yeah.

The point is again to to operate it when it's going to achieve the desired effect and not before, and which is really I mean, this is where it gets hard to talk about this, because the desired effect is so mind numbingly awful. I'm trying to speak of it in any scientific, clinical sense. Yeah, it's it's a little rough. So there there are two different ways to create a supercritical mass within a fission based bomb. Uh. And actually both of these ways were used in first two nuclear

weapons ever actually used in battle. Um. One of the things that I think of is uh again in in a clinical sense, but it's it's still kind of amusing to me, is in reading about this. Um. The nuclear weapons that were detonated in Japan too, uh, or I should say over Japan to UM end the Second World War were really I mean, it seems like, well, they did what they were intended to do, but they were really more like lab experiments packed in a case and and and created. So I mean, now things are are

pretty standardized. But the two those two weapons were very different and the way they did things and uh and really they the scientists weren't dent certain that they were going to do what they thought they were gonna do. Yeah, and those two weapons were called going to do this, we're called Little Boy and fat Man. Yes, little Boy was the one that was dropped on Hiroshima on August six, nineteen, and Fat Man was dropped over Nagasaki on August nine, ninth.

So these two use two different methods to initiate this supercritical mass and begin the nuclear fission process. A Little Boy used what was was called a bullet. It's uh, you, in order to start this whole reaction, you have to have something that's going to create neutrons. And in this case, it actually was a bullet, although not you know, in

the sense of a gun. The gun that fired it was not the kind of gun that we would think of necessarily, right, This was a So you take take a ball of uranium two thirty five, all right, and then you take a small amount of that two out as a bullet. It's a projectile. It's placed at one end of a long tube. It's got explosives, behind it. So when the explosives go off, it propels the bullet down the tube until it impacts the sphere of your aim two five at the other end. And uh so

the here's how it. Here's what happens. The explosives fire, the bullet goes down the barrel, the bullet hits the sphere, and it hits a neutron generator. Like I said, you have to have neutrons to start this fission process. So just dropping uranium two thirty five, that's not that's not going to cause a huge explosion. But by creating these neutrons with this neutron generator, uh, it ends up starting

off that that series of reactions within the bomb. So once those neutrons are generating, starts saying the uranium two thirty five, the fission reaction begins. The individual atoms of uranium two starts to split, and they too start to eject neutrons, which causes more uranium two thirty five to split, and that reaction continues and the energy builds up until the bomb explodes. So that was the little Boy version, by the way, in case you're wondering how little Little

Boy was, uh it was. It well it was able to drop a bomb that was equivalent to fourteen point five kilo tons of TNT. Oh wait no, umah, so yeah, so little is a as a relative term. And then we have fat Man. Now fat Man used an implosion triggered bomb. Yes, this is this is different from the bullet method. And what happens here is you've got a sphere of the nuclear fuel. So in this case again uranium to thirty five and then you have plutonium to

thirty nine core. Inside that and and and surrounding the two nine core are some explosives. So what happens is in this bomb, the the sequence of events is the explosives around the plutonium uh fires and that creates a shock wave. The shock wave ends up compressing that plutonium to thirty nine, and that compression is what triggers the fish and reaction within the plutonium. That reaction becomes a chain reaction again and the energy is build up and

then the bomb explodes. So the whole way that this works is that it it creates and then directs that shock way from the uninitial explosion to generate that first fission reaction that becomes the chain reaction. So yeah, a little different from the bullet method. Uh, and it was it was interesting, you know, both of these methods were being worked on at the same time during the Manhattan Project. And uh, actually the implosion triggered bomb. As I understand,

it was the very first method that was tested. Who's the trinity bomb that was tested, um back in Los Alamos, which was not a prime real estate if back in that time because of all the nuclear testing they did. In fact, back when they did that first nuclear bomb test, no one really knew what the result was going to be, right,

I mean, there's just no way of knowing. And uh, it turned out that several of the scientists who are observing the nuclear bomb test back in Los Alamos temporarily lost their vision because the the explosion was so bright that it damaged their eyes. But they were able to recover their vision after a while. But people didn't know how powerful this was going to be, how intense the energy was going to be, and so they were viewing it with their naked eye, and that turned out to

be a mistake, right. And of course, uh, an explosion of that magnitude also spreads radioactive material over a very large, uh physical space, so uh, you know, we were talking about that a few minutes ago. When there is a nuclear explosion like this, if there is UM, you know, it spreads nuclear material out over an area. Basically you could think of it in roughly if you're taking weather out of the picture. UM, you know, you would have

a huge circular ish area over which this material is spread. Now, of course, if the wind is blowing um, you know, or you know, the temperature is right, the the material can drift along with the wind. It can uh, you know, get into water supplies, it can you know, cover it can move quite a bit UM. And you know, the the effects the physical effects of course, UM. You know, there's there can be a lot more than just h vision problems. I mean there's there's there's cancer has been

attributed to it. UM. There have band cancers attributed to it UM and many many other physical conditions UM related to that. So it's not just the people who are atomized, if you will, by the bomb right as they are. They happen to being close enough proximity that it can have long lasting effects on on many many other people and can make the area radioactive for many many years to come. These these elements that are experiencing radioactive decay. They can be in this state for hundreds of years,

depending on the materials. The Yeah, the essential if you are if you're at ground zero of a nuclear explosion, which is which is essentially right at the center of the explosion, the the the location of the detonation. Essentially, um. The the thing that would kill you be the heat. The heat would be so intense that you would you would be essentially vaporized. Um. But following the heat is the pressure that's created from the shock wave of the explosion.

And so let's say that you're far enough out where you're not going to be vaporized by that heat, that pressure could be enough to knock over the building you're in totally. It could crush you. So you have that to look forward to. Then you've got, like like Chris was saying, the radiation and the radioactive fallout, So you can think of that's sort of a bull sye target, right, Like the very center of that target is where the

heat is going to be the most intense. Just outside of that is the general area where the pressure from the shock wave is going to be intense enough to be deadly. Just outside of that is the radiation where the radiation could be strong enough where you're you could suffer severe radiation sickness, uh, just from the exposure from that.

And then the radioactive fallout could affect the largest area, right, And like you were saying, the weather can end up carrying particles that have uh this radioactivity to them and contaminate other areas miles and miles away from the site of the bombing. It can affect living cells, uh, you know, preventing them from behaving normally. I mean, they can cause birth defects in in future generations. UM. So this is

this is very very serious stuff, of course. Um. Now later after the wasn't one of the things that they realized after uh using these weapons was these these fission bombs work very well. Obviously they're very effective. But um they began thinking that, uh, perhaps fusion would be a more effective or create a more effective weapon. And that's the course they began following, right, And they in some

cases they first started looking at fusion. Back in n there was a physicist by the name of Edward Teller, and he came up with an idea called boosting. And this is a process where you create a fusion reaction in order to generate neutrons, and those neutrons then go on to create a fission reaction. So it's a hybrid really. Uh. Now, like we said, fusion is where you've got the two atoms that combined together to form a heavier single atom, and in that process it gives off quite a bit

of energy. Uh. And you can use different kinds of atoms to do this, but typically in a thermonuclear weapon where talking about hydrogen and hydrogen has different isotopes, right, there's uh, deuterium and tritium. Yes, and this is all talk. Normally a hydrogen atom uh just has the one proton, Yes, But if you add the if you start adding neutrons, then you get deuterium and tritium. And deuterium is stable. If you have a deuterium atom, it's stable. It's not

gonna decay. You can actually create water with deuterium, but it will in in enough, in large enough amounts. Deuterium is toxic, so it's not something you want to have around you. Uh. Is that heavy water? Is that heavy? You know what I couldn't tell you I remember about

heavy water? Is uh from Batman? It would it would, but then you think, you know, it would make sense in a in a in a sense because deuterium, you've got the neutron at it, which means that the actual atom itself is heavier, which means any molecule created out of that atom that would take the place of the normal isotope or the the the natural state of that atom would be intern heavier. Sorry, you can keep talking.

This is one of those times when, uh, it's something didn't click to me until we were actually talking about it. I'll let's see if I can find something. And I'm not a nuclear physicist, so I honestly can't answer all those questions off top of my head. But tritium is not uh stable, it will it will decaytive relatively quickly. So it's a bit of a challenge. But what what is it, Chris, Yes, d t O deuterium. It's it's

water made with deuterium. There you go. And so trying to create a effusion bomb is a little bit tricky because tritium is one of those elements that is typically used in these but it is not it's not easy to store, and it's uh got a very short half life. So so if you have the problem with storage and how do you keep tritium stable so that you can have a fusion reaction in order to start off the fission that's going to ultimately lead to this destructive force.

Scientists came up with a fairly creative solution. First, they created a lithium deuter rate, which is a solid compound, and it does not have the problem of undergoing radioactive decay at room temperatures, at normal temperatures or even you know, normal operating temperatures of a nuclear bomb until you detonated. We've got a bit more to say about how nuclear weapons work, but before we jump into that last segment,

let's take another quick break to thank our sponsor. With the tritium problem, they began to rely upon a reaction of fission reaction which will produced tritium from lithium. So first they have to induce a fission reaction with the lithium, and then the lithium in turn will produce tritium, and then you've got the uh chance, You've got the the the right elements in place to have the fusion reaction,

so you have fission to fusion to fission again to boom. Yes, it's a little complicated, right, and uh, that fission reaction with lithium, it also gives off a lot of X rays, and the X rays are actually what allow uh. Well, the X rays end up increasing the temperature within the bomb, all right, And those that increased temperature and the pressures that are associated with it are the that's the energy that goes into the system that allows fusion to happen.

Because this is one of the tricky things about fusion. You gotta pour energy into the system in order diffused two atoms together, right, And the components of the bomb are separated by casings that prevent accidental or or or maybe premature detonation, so that that initial explosion uh and causing the X rays basically uh causes the deterioration of those materials and allows the bomb to continue detonating. Yeah. So let's it's it's it's a little competed to talk

about this without an illustration. Yes, But the way this fusion bomb would work is that you've got an implosion fission bomb with the cylinder casing of uranium two thirty eight,

which is acting as a tamper. A tamper is the thing that is controlling this reaction so that you get as much energy involved before it actually unleashes an energy um The within inside that that tamper of uranium two thirty eight is the lithium deuteride, and there's also a hollow rod of plutonium two thirty nine in the very center of all that. And then separating this this cylinder of a tamper of the the uranium two eight from the implosion bomb is the shield of uranium and some

plastic foam. And this is what once you start detonating at the sequence of events, is that the fission bomb. So that first explosion goes off and this generates the really intense X rays which increased the temperature and the pressure within the bomb. Uh the shield, that uranium two thirty shield with the foam, it actually is what keeps that contains that that explosion so that it does not

prematurely detonate the rest of the fuel. But the heat causes the tamper, that cylinder of the uranium two thirty eight to start to expand and it begins to burn away. It starts to put more pressure on the lithium deuterate, which is squeezed so hard that it causes shock waves that initiate fission within the plutonium rod. So here's you got your second fission reaction. So you've got the first fission reaction which causes the shock wave. Ultimately that begins

a second fission reaction within the plutonium rod. Now that reaction starts to give off radiation, so it begins to to expel neutrons, and it also gives off a lot of heat, So now you've got even more heat in addition to the heat that was generated by the X rays. The neutrons go into the lithium deuterate, which then combine

with the lithium and that makes tritium. So now you've got this environment of incredibly high temperature, this incredible pressure, and it allows the tritium and deuterium and also deuterium deuterium fusion reactions to occur. So you've got tritium combining with deuterium and deuterium combining with itself in these reactions, which produces even more heat, more radiation, more neutrons. Those neutrons from those fusion reactions induce a final fission reaction

in the uranium. Two pieces that are making up that tamper and the the shield that's around the whole thing, which of course creates even more radiation and hate, and then the bomb goes boom. So you've got these this series of explosions going on in a fusion bomb, several which are fission, one of which is fusion. The reason for that, you may wonder, well, why do you need

so many reactions to go on for a bomb to explode? Well, when we were talking about Little Boy, Uh, the interesting thing to me about Little Boy is that it was incredibly destructive weapon, but only one point five percent of the material, the fission norble material within that bomb actually underwent fission one five percent, So it could have been even more destructed. Yes, the energy it unleashed could have

been orders of magnitude larger than it was. So a fusion one, a fusion bomb is designed in part to try and create as efficient a series of explosions and reactions, really, we shouldn't even say explosions, reactions within the bomb, um as as many as possible, are as much of that material as possible, so that what it does detonate and unleashes the largest amount of energy it possibly can for

the the amount of payload that it has. Now, this also means that we have been able to reduce the size of the actual payloads because we can create just as an effective and explosion but with a smaller amount of material as we could from several decades ago. Yeah, the weapons these days are far more reliable than than those early ones. UM. And we've gone from dropping them from planes to mounting them on cruise missiles and i

c b ms intercontinental ballistic missiles UM. And of course, uh, you know, these these weapons now travel under their own power at a certain point anyway, and um, you know, the the i c b ms can they actually leave the atmosphere and re enter the atmosphere, so they can travel very very long distances that way. UM. And we we wouldn't really be able to to accomplish that if we hadn't moved to a fusion method where we could be so efficient with the way that we eliminate the

existence of other people on the planet. I hate to put it that way, but you know, ultimately, even though we're talking about something that's really scientific, the application of this is absolutely horrifying. But it's not able to get

away from that. But the uh, yeah, because if if we hadn't done that, if we hadn't come up with the fusion process, then it would be much less efficient and we might not have the option of putting something on a missile because it would the payload could be too great for for a missile to be uh practical, because at that point you would have to build a missile that would be able to carry enough fuel so that could propel both the missile itself and payload to

wherever it is you're going to send it, and it could just become a matter of scale and and it just would not be It would be possible, but not practical. Uh. By making it way more efficient, we can now put it on top of lots of stuff, including you know, not just missiles, but weapons aboard submarines. I mean that's all sorts of stuff, right, So terrifying in a way, but yeah, we we have we have Einstein a thing

for it. So the next time you see that guy. Well, um, one of the things that I wanted to mention too, And we don't have to get into it in great depth because we're getting there as far as time goes. But um is the testing of these these weapons traditionally. UM. Of course, as Jonathan mentioned earlier, in the very very

early days before they had been actually used. UH, scientists wanted to test them to to find out if it was even possible to make uh the weapon of mass destruction they envisioned to to to see exactly what it would do, how well it would work. UM. So they did all this testing outside UM and above ground. Now they've a lot in a lot of cases they've done well. They've done tests pretty much in all sorts of forms.

I mean, they still do them outside, but UH in a lot of cases now they UH weapons engineers do this underground UM in an attempt to contain the reaction. Of course, although it UH a nuclear reaction can produce such force that it can vaporize large amounts of rock, so they have to be very careful where they do this. UM. You know, for a long time, many governments around the world would use UH islands to to test their their weapons,

places that they felt were uh somewhat unoccupied. UM. And for for example, UH actually that inspired uh the Godzilla series of movies, UM, where they a lizard irradiated on an island. Where. It's a great series of documentary documentaries where UH, the the the the one, the one, lizard who was irradiated by this this nuclear explosion turns into Godzilla and not you know, all of the other animals that happened to be living there. Um, he got just

the right amount of dust, apparently. So UM. They've tested weapons underwater, UM, you know, and in space, but people are gradually moving to computer testing, UM, which allows scientists to get a much better idea of how things might work without having to actually blow something up, actually blow something up, uh and create the environmental conditions UM, the the fallout and and reactions that would follow UM. And

they've found that this can be actually beneficial. I was reading an article I believe it was in the Washington Post. It was saying that uh uh computer modeling had allowed engineers to discover problems that they hadn't realized existed with the weapons system that they built, UM, and uh prevented it from becoming you know, they re engineered the weapons that were in existence because there was a possibility that it may not then it may cause problems and wouldn't

be a stable um. And uh, you know, it's it's interesting. But of course they've found out through testing that that fall out can travel UM through air currents and water. And Uh, I think that's one of the things that leads to um fear that keeps people from using nuclear weapons more freely because people really understand now more than they did um years ago that you know, this is

not something that should be done casually. Yeah, there's also the fear the hypothetical nuclear winter, yes, which you know, the particulate matter from multiple explosions basically causing clouds above the earth right, which would block the sun's light from reaching the ground, thus killing off a lot of the plant life that depends upon sunlight. And then that ends up that ends up killing off the species that all depend on plants, humans being one of them. So it

could end up being a global extinction event. It could also be something where it just changes the climate globally where you know, we actually do have a really harsh winter because the sun's light just isn't hitting the surface and warming it the way it usually would. Uh. And we see we see things that could point us into like suggest that that's true by by things like like a volcanic eruptions where a lot of matters is ejected

into the atmosphere and it can affect uh, local weather patterns. Now, when we're talking about a nuclear winter, we're talking about something that would last longer than a you know, just a month or two. So it's pretty it's a it's uh, it's one of those doomsday scenarios. It's a sobering thought, to be sure. Um. And uh, you know, it's one of the reasons I'm interested in this is, you know, to see the flip side, you know, the idea that that nuclear energy can be used as a very efficient

and clean source of power. Of course, we saw we we talked about the Fukushima um reactor last year right after it happened. Um, but that's not the same as an intentionally intentionally using nuclear power to cause the destruction of many people. So um, it's it's amazing to me personally that a little tiny atom can be used to do these amazing things, whether they're you know, and I mean amazing and instructive or destructive. Uh, it's it's amazing.

It is amazing, And we'll probably I think what we'll need to do is in a future podcast, we'll have to do a full episode just on the Manhattan Product Act. Because the if you look at a list of names of the people associated with it. If you've ever taken any any classes in physics, you're going to recognize a lot of those names. I mean, the era that the Manhattan Project existed in was remarkable in the sense of it was it was an unprecedented era of scientific exploration

and innovation. UM. One of those where you just it was phenomenal the amount of of UH work and scientific discovery that went on at that time. UH and in no small part that was due to things like World War And that concludes this classic episode How Nuclear Weapons Work. Chris and I originally recorded that episode on April fourth, two thousand twelve, and obviously the world has continued to depend upon the threat of nuclear weapons since then. We have not been able to get rid of them all.

We haven't had a magical Superman for incident where a super powerful alien comes down to Earth and throws all of them into the sun. So again, I think it's important to just know how these things work and hopefully we never ever have to worry about it in a more practical sense. If you guys have any suggestions for future episodes of tech stuff, maybe it's a technology, maybe it's a company, maybe it's a personality. And tech send

me a message. The email address is tech Stuff at how stuff works dot com, or you can drop me a line on Facebook or Twitter. To handle at both of those is tech Stuff H s W. Don't forget. You can also follow us on Instagram and I'll talk to you again really soon for more on this and thousands of other topics because it have stuff works dot Com two