Matt Bunn - How Nuclear Bombs Work

and unequivocally over and over again it was Matthew button if you have to see Matthew but Matthew button so we found you and that's what we're about to hope and discern through your thinking and about this all right good um so thanks for having me here it's a pleasure to be here I'm here to go on for a while because we got a lot of different things to cover we're going to talk about how the basic principles of nuclear weapons how nuclear weapons are made what the hard parts are making nuclear weapons but also the nuclear materials that you need to make them and I'm gonna use a number of different things I probably should have had some video in the in the powerpoints but I didn't bother but let me start off with this object here this is this is actually a fake but it's only aluminum but it's from a facility in Russia an attempt by the audience gets the Institute for physics and power engineering at this facility they have 80 sounds in the desks about like this that are made of either weapon-grade plutonium or weapon-grade uranium you can take about a dozen of them and pop them in your pocket in the case of plutonium about 80 of them would be enough for a bomb when we got started when I first went to the Institute for physics and power engineering they didn't have a fence around the building where these things were they had a fence around the overall facility but it had big holes in the fence and so on these things weren't in a vault they were sort of you know skynyrd out on the table and so on and like this they were blank and there were a bunch of aluminum ones so it would be a trivial matter to substitute a bunch of aluminum ones for the plutonium ones they had no detector at the door to set off an alarm if somebody was carrying on a bunch of these in their pocket so that's just an indication of it's worth knowing a little bit about the technology so you can start thinking about well what is the risk of a situation obviously you didn't need to know a whole lot about the technology to realize that that was a risky situation was interesting is thinking about how how could it get to be that way in the first place yeah what was the Soviet Union run by a bunch of idiots now it wasn't run by a bunch of idiots they were designed that facility for a world that no longer existed they weren't thinking in Soviet times that you were gonna have you know a bunch of armed guys storming a nuclear facility to steal plutonium that wasn't gonna happen this was a controlled Society of the 7th Union they weren't really that worried about insiders stealing stuff either because where on earth would they do that if they are an insider in a nuclear facility that means they're closely watched by the KGB they can't leave the country without being watched by the KGB they can't be with a foreigner inside the country or that they watched by the KGB how could they possibly sell it or do anything with it they key security concern that they had that they designed their new their nuclear security the deal west was Western spies since this was a primarily civilian facility Western spies weren't an issue therefore no need to invest much in security at this particular facility and so that was designed for a closed society with closed borders everybody under close surveillance by the KGB and nuclear workers who got the best of everything that society had to offer and all of that had gone away so we really faced it an interesting crisis I came under the government and we started getting these cables from Moscow from a friend of mine by the name of Ken Fairfax who had managed to really penetrate the Russian nuclear system in a very interesting way which one of those cables had the wonderful title holes in the fences security at Russia's nuclear cities because Russia had by the way entire cities devoted only to the production of nuclear they're essential ingredients so anyway at the end of this talk what I hope is that you will understand enough of the basics of the physics and the technology of nuclear weapons to understand what are the hard ones in making a nuclear bomb what are the what are the kinds of different risks that might be posed by for example the spread of nuclear reactors versus the spread of uranium enrichment plants and we'll talk about what those are oh so with that said let me get started let's say I don't want to get the PowerPoint up first of all there we are okay okay okay so almost everything about nuclear weapons and nuclear energy arises from one very basic technical fact and that is that you get a huge amount of energy out of each atom compared to each atom in a chemical reaction so what happens is a neutron comes in and it hits an atom like this a really big atom with lots of protons and in this nucleus and lots of neutrons in this nucleus how many of you are from either of physics or a chemistry or background of something like that okay not very many what I'll bet a lot of you know what look like charges do if you have two things that are charged the same you try to put them together what are they going to try to do repel right so you've got 92 protons in this nucleus one Hertz aren't they flying out into the surrounding countryside and repelling each other it's because of the nuclear forces the strong and weak nuclear forces and the neutrons are sort of a glue that helps keep those this atom together but it is a lot of no static force trying to throw us out that has to be held together so the neutron comes flooding in and it wax left atom and it puts it in a sort of vibrational mode and if it gets far enough apart so that it's gets sort of long then the nuclear forces can't any longer hold those electrostatic repulsion forces in and it splits apart into two different pieces okay these are what are called efficient products and by the way this stuff is not especially when you acted this but these atoms hardly ever fall apart by themselves they have a half-life which means the time for half of the material to decay to something else of three-quarters of a billion years all right so this is this is not stuff that falls apart very often these fission products on the other hand are extremely radioactive okay and it releases two more neutrons on average sometimes it releases one sometimes it releases none sometimes release it's more than two on average about two how many people would like to know what a neutron is okay all right let me back up yeah all right so the basic structure of the matter that we know I'm not going to get into all of the the real particles that you need little particles but the basic stuff is neutrons protons and electrons so protons have a positive charge neutrons have no charge electrons have a negative charge the way an atom is structured is the nucleus is where the protons and the neutrons are in the middle and the electrons are in a swarm sort of a cloud you'll be in high school you'll see they go around the atom not true they're there in a sort of probabilistic haze around yeah an electron is an odd little entity it doesn't actually exist in any one place at any one time and it really it's really is sort of a haze kind of a thing shouldn't think about it like a billiard ball you should think of an electron as a sort of haze of probability space bits and actually you should think about new types of protons that way too but it's a lot easier to think about them in bigger calls the so a neutron is a neutral protocol and basically the whole all the matter around us is made up of a fairly small number of elements basically less than 100 there are more than 100 elements but is it ones above one hundred are ones humans created definitely exist for periods of time then go back to the matter around this made up of elements and each element is defined by how many protons it's got it has new place so hydrogen has one helium has two uranium has 92 plutonium the other material we're gonna hear about a lot about today as 94 okay yeah so when you talk about you are eyes and junior so when you talk about the the actual splitting of the new press the sort of energy we think about is that all electric electrostatic repulsion of the nuclei basically it's all coming from the electrostatic repulsion in the nuclei so you end up with about 200 million electron volts coming out of that now the electron volt isn't any amount of energy but they don't it's only an interesting amount of energy when you think about this happening millions of times okay or trillions of times our quadrillions of times or quintillions or septillion does that mean it gets so that you can't like keep track of what the prefix should be because the numbers are so big but it's about a million times more per atom than you get out of chemical reaction by the way so an element is defined by the number of protons and then an isotope of an element which are different kinds of the same chemical is defined by the number of neutrons plus protons so this tells you the atomic weight of this guy roughly so uranium-235 has 235 total things in its nucleus neutrons plus protons and each of those has a mass of 1 on this unit of atomic mass scale and so it has an atomic mass of about 235 okay well because the electron has it all for all intents and purposes an electronic map Tomic mass of 0 I mean it's not exactly 0 of course but no small compare to these guys all right and by the way one of the things that many people don't realize is that all of us are mostly empty space so if I am if my thumbnail is the nucleus of an atom then the electrons are over here and everything else is empty space basically so it's amazing that we end up seeming solid to ourselves given that we're basically Muslim so what happens is the thing splits apart and because these now have a lot of you know they've got a lot their books got a lot of protons in them they're gonna fly apart really high speeds up almost all the energy that comes out it's actually in the kinetic energy of these fission products just flinging out from this reaction but the important thing is these two neutrons because they're what cause something else to happen and those of you who ever have ever thought about like the growth of bacteria or things like that if you have something that goes 2 4 8 16 it doesn't take very long before you're talking billions to trillions quadrillions etc and that's what happens in a nuclear chain and so this fact that you can get this huge amount of energy per atom means that with a relatively small amount of material you can release a huge amount of energy which means that you can make nuclear power with a very small amount of fuel so for example if you have a 1 gigawatt power plant that's a coal plant it needs an 80 car train of fuel every day ok if you have a 1 gigawatt nuclear plant it needs half of one of those cars once a year ok totally different ballgame ah but it also means that you can make instead of having to send hundreds of aircraft again and again and again it's a bomb a city as we did when we were bombing Tokyo during World War two you can have one aircraft dropped one bomb that will destroy a city ok that this and it's this key fact that 200 million mm both as opposed to maybe you know three four or five electron blocks for a typical Oh chemical reaction there's a wonderful story about one of the key people who got the Manhattan Project started a man by the name of Leo salar he was a Hungarian Jew and he had fled Europe because the wool more - hadn't started yet but the clouds were coming and he was living in England and he was eating breakfast one day from reading the newspaper and he saw that Lord Rutherford the discoverer of the neutron by the way had said quote anyone who thinks you can get energy out of the atomic nucleus is talking moonshine right and the reason Rutherford said that is even though this might be a lot of energy on a per atom basis it's it's a ridiculously small amount of energy unless it happens to 'silly ins about us so this is 200 MeV is much less than a jewel and a jewel is the amount of energy it takes a fly to do a push up okay [Music] so we're talking teeny tiny amounts of energy unless ghazan overdone but in the nonetheless look Rutherford statement annoyed salar cuz he always thought you know scientists should never say something is impossible unless it really but you know that violates a physical law or something and the Lord went out for a walk and he was thinking about this and being annoyed about this and he remembered that there were certain chemical reactions where when some of the molecules underwent the reaction that catalyzed others of the molecules to undergo the reaction and the reaction started and it was called the chain reaction and the reaction started might faster and faster faster faster until all the material had reacted and he thought about that he thought about as he stepped off the sidewalk to cross the street he thought what if there is a reaction that somehow does that was nuclei with the energy in the nucleus and by the time he had gone to the other side of the street he had thought of cities laid waste by atomic bombs okay so then he started thinking well what kind of reaction might that because fish and haven't been discovered yet when he was having us these thoughts to himself and he went off on some completely wrongheaded directions and he didn't have a lab of his own at that time he started begging space and various other people's lives and doing various experiments that went nowhere eventually moved to the United States was continuing to any of what he did he realized that this wasn't a potentially important idea and he wanted to keep it secret but he wasn't a member of the government so he couldn't you know stamp classified on her whatever and the only way you could think of to keep it secret was he took out a patent which at that time you could have a secret war patent right and so we took out a patent on the idea of the atomic bomb way back and this was in the mid 30s anyway good talk to United States he's still sort of in his spare time working on you know is there some nuclear reaction that might have a chain effect like this but he's not getting anywhere and finally he decides you know all the things I've tried are going nowhere you know this obviously is not possible and he sends a cable to the British war office saying you know it's okay can release that patent there's obviously no such reaction alright and then it comes down with the yellow fever how many of you heard this story before by the way anybody okay he comes on with yellow fever he's lying in the hospital near Columbia in Manhattan and somebody comes and describes to him the instrument had just discovered that atoms can be split and he's this is what makes a large amazing he's lying in the hospital he's still feverish from yellow fever and immediately thinks wait a minute those two fission products aren't going to be stable with that many neutrons it must also release at least two neutrons per atom so you know he's just lying there and he fixed this and he literally he drags himself out of the hospital bed he goes down to the Western unit and he sends a cable that says please disregard previous cable stop the Salar and then he was the one that drafted the letter to Roosevelt that Einstein signs it more or less got that Manhattan brought you yeah all right anyway enough on this one slap so let's switch over so the obvious question is let's see so this question is the obvious question is how do I arrange my nuclear material so I can actually make this reaction happen okay so if what I have in my hand a ball of uranium that's not enough to sustain one of these chain reactions and a neutron wings in it and starts causing some visions this is what's going to happen here are the atoms blowing around neutron comes in splits it out on you get a couple of fishing products and the neutrons go flying out into the surrounding countryside without causing any more efficient maybe they might you know one out of it cause one more efficient or something like that it decays out so that's what so that's what's called a sub critical mass it's not enough material to be critical meaning to sustain this nuclear chain reaction well what if I put some more material in let's see if I can actually find one transparencies here alright so then I put some more of those atoms around the outside and then it gets to be that the probability that a neutral that each Neutron is on average causing more than one other efficient to take place and that means the nuclear reaction is growing rather than decreasing and you have a chain reaction now it turns out that making a chain reaction happen is not that hard to do I had enough highly enriched uranium in this hand they're not finally returning him in this and and I simply brought them together they would start having a nuclear chain reaction okay now why is that not a nuclear bomb what would happen if I did that anybody know yeah we'd have to do with the rate at which it would have a high power but it would still have so that's that's getting there that's getting there yeah ready it's gonna create radiation sure because there's going to be these neutrons from these fish right right right sure it's gonna be worse than that it's gonna kill me dead for sure aren't the two pieces I'm gonna yeah there you go and what happens when they heat up right but something gets really really hot what's the first thing it happens - it turns them on solid to a liquid and then it turns to a right so they're going to turn to gas and they're gonna expand and then these atoms are going to be far enough apart that the neutrons are going to be flying out of the surrounding countryside again and the reaction will stop so basically the stuff blows itself apart without giving you a decent reaction what what happened is I would you know we'd get this massive shower of neutrons I'd die probably everybody in the room would die and that would be that and we wouldn't manage to you know destroy it all event for the way we could with an actual bomb okay so how do we solve that problem what we need to do is figure out a way to get our critical mass together fast because it turns out that there are always neutrons around when you have this nuclear material you can't just say okay there's not gonna be any neutrons until I put one in it turns out that every once in a while I'm not very often but you know there's gazillions of atoms in this critical mass so it happens and often to worry about what is atoms fault fishings by itself and releases a couple of neutrons turns out that happens a lot more like millions of times more with plutonium and in particular with what an isotope called plutonium-240 plutonium-239 it turns out I'll talk about this more later is the one you want for your nuclear bomb plutonium-240 falls apart all the time and so when you and it's inevitable when you make plutonium 239 you end up making something 10 into 40 more or less by accident so you have lots of neutrons flying around and in fact in the Manhattan Project they originally had a bomb design that didn't work well if there were a lot of neutrons flagrant and because they didn't know that fact about plutonium because they had only discovered plutonium a couple of years before and they were just starting to make it and when they realized there's lots of neutrons from the plutonium then they have to sort of rethink completely what they were doing in their bombs I don't we'll talk about how they did that more in a moment alright so another thing you can do if you don't want to use so material you can also have something that would reflect the neutrons back in and that reduces the total amount of material you have to have in order for each Neutron to on average split somewhere out okay now I've drawn it as you know perfect reflectors like a mirror there ain't no such thing that four neutrons but there are things that like neutrons pretty well and actually lots of stuff reflects neutrons reasonably well you know steel beryllium wax if you put your mind to it will reflect neutrons to some degree so and a real nuclear bomb you pretty much always have something around the nuclear material acting as a neutron reflector okay so there are basically two ways that people have thought of to try to get the stuff together fast enough that a whole bunch of it will fishing before it all turns to gas and blows itself apart this one is the simplest it's called the gun type bomb and the reason is because it's basically a gun that fires a shell of my enriched uranium into another piece of highly enriched uranium okay so you've got a gun barrel we've got some explosive got a few silent majority we've got another piece of the rich uranium and you fire one into the other this thing is called The Temper off but it is also the neutron reflector so what the tamper does so again what's stopping your reaction what's stopping your reaction is the stuff turning to gas and expanding out and then and then it gets to the point where the atoms are so far apart that the neutrons aren't hitting them anymore and they're flying off in this yearning countryside so you'd like to stop that gas from expanding out but there ain't no such thing as a material strong enough to hold that gas in with the amount of pressure and energy that it's got but just inertia a lot of mass you know we'll take another couple of microseconds maybe for that gas to expand out or tenths of a microsecond all of this stuff happens incredibly fast there's less than one by second is when all the energy is released in a nuclear bomb so less than a billionth of a second all right now think think about that so the Hiroshima bomb just as an example was a roughly a fifteen or sixteen kiloton bomb now what that means is that it's fifteen or sixteen thousand tons of conventional explosives equivalent so for example if you have a coal train those coal cars carry 100 tons roughly so we're talking about a train that's a hundred and sixty cars law carrying conventional explosives that's a huge problem if you think about it now now think about all of that energy is being released in a millionth of a second less than a millionth of a second in a ball of nuclear material about like yay okay all right so what are the conditions so if anybody who knows say the ideal gas law or whatever so we have obviously there's gonna be a huge temperature in here right so if you and it hasn't that time to expand yet so if you have a gas and you increase its temperature to roughly the temperature of the surface of the Sun of the center of the Sun actually tens of millions of degrees in this ball what's gonna be true about the pressure it's gonna skyrocket right pressures can be we're talking millions of pounds per square inch okay in this little ball all right so then we have this ball of unbelievable energy okay unbelievable temperature unbelievable pressure and then it just flies out okay so the first thing it does is it shoots out this amazing bursts of gamma rays and so on because of this incredible temperature everything is ionized everything is just read eating like mad I annoys means the electrons are stripped off of it it's an incredibly high temperature and those gamma rays and radiation and so on heat up all the air around it and it creates this unbelievable fireball that absolutely turns to gas just incinerates anything that's inside the fireball people buildings whatever if it's inside the fireball it's gone okay turn to gas yeah your name is Joel no all right we're getting there I'm gonna do a sort of series of the effects so we've got this initial burst of neutrons and gamma rays okay then we've got this fireball coming out and we've got from that initial pressure we have this shockwave going out and of course in the pressure is most intense when it's small as it gets bigger and bigger and bigger and bigger the pressure the pressure at that shock front will get less and less and less but it's amazing you'll have enough pressure to destroy buildings a long way away and of course how far away exactly depends on how big your bomb it also depends interestingly enough on whether you detonate it right at the ground or a little bit above the ground if you definitely don't right at the ground the bomb spends a lot of its energy digging up the ground okay if you detonate it above the ground then you have this interesting reflection effect where some of the some of the blast wave goes down and then gets reflected off the ground and combines with the stuff that came out directly and you get what's called the mock reflection going out in this blast wave that it sort of enhances the blast wave and so if you want to knock down buildings and stuff like that an air burst is the way to go if you want to destroy things that are built to survive nuclear blasts then you want to go for something pretty close to the ground even right on the ground all right so one of the ways to do it is with this very simple gun type bomb so the bomb that obliterated Hiroshima was literally a cannon that fired a shell of highly enriched uranium into rings of highly enriched uranium that's basically what there was to it will I don't care what you wore that was again a 15 kilotons bomb or 16 or you know measurement wasn't that great back back at that particular moment they had they had a bummer and they had one other plane to try to dick some measurements yeah my question is this gun type of explosive compared to conventional cannons or how much more powers in nothing propone is totally normal okay you can use c4 you can use TNT you can use you know blasting caps you know there have been proposals to use of this their press but separate lessons you need to get this thing moving at something like a hundred meters a second that's what yeah in the back so what caught what actually what causes the detonation is that there are neutrons around in the Hiroshima bomb they did actually have a neutron what's called a neutron generator that set a shower of neutrons it's just the right moment they've done it didn't actually need one as South Africans built a gun type their weapons with guns I bomb then apparently didn't bother with a neutron generator because as I say the atoms occasionally do fall apart by themselves and generate their own neutrons okay but so as these pieces come together you're when you get to about say here you've got a critical mass so if a neutron gets generated at that moment the reaction is going to start so what you ideally want yes for the not to start until they're all the way together because otherwise they're going to be starting to blow themselves apart before they've even gotten into the sort of optimal configuration to get as many neutrons now one of the things that's interesting is if for those of you who have done this sort of if you know how long would it take for bacteria to cover the Earth's if they doubled you know every five hours or whatever each generation of neutrons if each atom say is if the fishing of each atom leads to on average two other fishings that's a little more than it's really true but let's say that that was what was going on then the last generation of atoms getting fish and is twice as big as the one before it and that one is twice as big as the one before that so almost all of the energy is from those last two three four generations of fishes is like ninety percent of the energy is coming from those look so if you can just delay the expansion of that gas for just a fraction of a microsecond you can maybe double triple quadruple the yield of your explosion now what's interesting is it's actually remarkable how little how inefficient some of these things are so the hiroshima bomb for example only a tiny amount let me think about two percent of the nuclear material actually efficient in the hiroshima bomb and the rest would just sort of had to be there in order to make that happen yeah is it because Daniel sorry Daniel because the neutron shower like what to sir because you know are they not wholly together yet you know it's because this is just a inefficient way of doing things so let me show you the more efficient way of doing things so yeah you can somehow figure out how to compress your material so that those atoms are really close together then when it atom splits and says have some neutrons it's much more likely they're gonna hit another atom right away okay so it turns out that the critical mass decreases roughly with the square of the density okay so if I had something if I had said the the critical mass of uranium if it's a ball without any reflect or a deterrent or anything it's about 50 kilograms okay weapons-grade uranium all right if I somehow managed to compress that ball so that it's twice as dense it's only gonna be one force of 50 kilograms that I'll need for a critical mass if I can make it three times as dense it's gonna be 1/9 okay so the question of how much do I need for a nuclear bomb depends on the answer to the question how clever are you in designing your nuclear bomb at being up the compressive so how could I compress that material well I'm gonna use conventional explosives to compress that material so what I'm gonna do all right so the Nagasaki bomb had basically a ball of plutonium unlike this picture it also had some tamper and stuff Reddit and then it had fast explosives and slow explosives arranged in these sort of lens type arrangements such that and they were detonated at many points around the sphere at exactly the same time so that you ended up with a shock wave that was going in sterically and crushed that ball down to a smaller size and they also had a neutron generator right at the mint right in the middle that set off a shower of neutrons right at the moment when that crushing had happened in fact it was the crushing that caused the neutrons to to fly out and that's that that made what had been a subcritical mass when it was not compressed into a very super critical mass much more efficient so the hiroshima bomb had about 60 kilograms of about of uranium that contained about 80 percent uranium-235 that's the rhenium 235 is the kind that splits easily uranium 238 is the other kind of common kind of uranium we'll talk more about that in a moment and of which only a kilogram or so actually fishing in the Nagasaki bomb they give had just over a kilogram that fishing but they only had six kilograms of plutonium in the pump so they had maybe 20% efficiency as opposed to maybe 2% efficiency because they had this implosion approach yeah I'm right is so the neutron generator was necessary including imbalances correct because everything here the big advantage one of the big advantages of the plutonium of the implosion bomb is that happens much faster than these two pieces moving together the compression happens you know at the speed of sound basically in this melt as the shock wave is going in how exactly and there's a reason for this yeah it's getting the hang of it but how does this exactly solve the problem of the background Neutron just because it happens a lot faster and so the probability that a neutron is gonna mess things up there's a lot small because it's not zero but it's lots more so in fact there's an interesting document from the Manhattan Project where Oppenheimer roughly estimates what are the probability of neutrons happening at different times during the reaction and therefore messing up the yield to differing levels of reduction from the expected yield and there was there was a decent chance that this would only have you know a few hundred tons of yield as opposed at 22,000 tons of yield that it didn't ended up having there's not a huge chance but it was seen on 4 or 5% chance that they'd only have a few hundred tons of you and then it's at least conceivable that that's what happened to the North Koreans on their first nuclear test so the gun type you can only use highly enriched uranium but the implosion type you can use either okay but the implosion type is tricky business because you've got to set off these explosives all around the outside of exactly the same time well that's with microsecond timing one of the to me the most troubling documents that the IAEA is in possession of related to Iran's nuclear program that really suggests yes they really weren't working a nuclear weapon design relates to a series of experiments involving a hemisphere of explosives with microsecond timing of the detonation around a ball of melon and there really aren't a lot of Sabbath civilian applications and that the document mentions a so of course the Iranian said this was a forgery all right the document mentions a foreign scientist by name who was helping with this program so the IEA went to the country of origin of this one scientist namely Russia uh and said do you know that Scott I said yeah we know what does this guy do for a living this guy is a he's a nuclear weapons designer for a living he designs implosion system he worked at naissance which is sweet like like the United States the Soviet Union had two main nuclear weapons design laboratories one established first and want us to have their second in the United States it's Los Alamos Livermore in Russia it's today referred to as Tsar often Schnee gents that used to be ours missed 16-inch Elvis 65 which were just postal codes in nearby open cities because the very existence of the nucleus with secret so then they said well was this guy in Iran and such and such a date guess he was in Iran at such-and-such a day so they went to talk to the guy I think I said oh you know it's edge naissance we came up with this great system for making nano diamonds using the nuclear weapons explosion technology that we had developed where you can crush this stuff and you know produces you know these tiny diamonds that are all useful for all sorts of industrial purposes so I was hoping the Iranian screen nano diamonds yeah there it is may have been mildly interested in our diamonds but I don't think that was the main purpose that project critically so this is what an early model of the Nagasaki bomb actually looked like so these blocks along the outside are where the explosives are going to detonate all right and you see there's a bunch of them and it's sort of a soccer ball tech arrangement it's kind of way here so you can see this is the it's much bigger than the actual plutonium ball this is the plutonium ball plus the tamper around the outside of it and you can see there's actually basically masking tape around I mean they had felt in there I mean this was this was you know put together with you know baling wire this is a let's say it's actually the way it's portrayed it's about life-size it's a little bit smaller than life-size said that the actual Nagasaki bomb would have been say from here to here approximately but the plutonium ball I'll have this little slide in a moment is this is one of the difficult things about nuclear security and nuclear smuggling is the amount of highly enriched uranium you need for a very inefficient gun type bomb which is bigger than the amount you need for an implosion bomb is about 50 kilograms or so so that fits in to two-liter bottles easily fits on the suitcase okay the amount of plutonium you need for a buff for an implosion type bomb you know fits in a cook camp um so once the stuff gets stolen and it isn't at the place where it was supposed to be it could be anywhere and all the later lines of defense are variations I'm looking for needles in haystacks so that's why I spend a lot of my time thinking about nuclear security because it's so important we'll talk more about that a little bit all right yeah let's see so we've done gun type on so you've got two questions here okay that's fine I'll make sure we've got that covered it's faster that's a hundred percent of the difference and so that if I could move my hands really fast I could do a gun type bomb without having to do all the complications right right basically what it means is that there's very little chance that during that time that those pieces are moving together after it has become a critical mass they've gotten close enough that it's a critical mass but before the point where it's really in the shape you want it to be to get a good yield that the reaction will start happening so there's if I'm just moving my hands together it's 100 percent certain the reaction walls started happening before we get a decent explosion out of it whereas if you are firing this stuff together there's some probability that will happen but it's a pretty small probability because the stuff it's moving so fast so people have done calculations for example about well what would happen if I had a big plate of my ministry I'm on the floor and I had you know 100 foot high building and I just dropped another plate of highly enriched uranium and you can actually from fairly straightforward physics calculate the probability of getting a decent yield out of that I'm not gonna go into that here but I'm set yeah if the if the method of making the gun type on this so simple that never so simple once you receive part measures do they have so that people can't just annotate it ah on the actual bombs themselves yeah yeah because it really seems very simple right so the simplest kind of such safeguards it's a good question what in the early days of the US nuclear program they just stored the the at least some of the nuclear material separate from the rest of the bomb and they didn't put it into the bomb until the bomb was ready to be used so that was called insertable nuclear complements but let's we've already I'm thrilled that you guys are so interested in asking so many questions but I got a lot of material to cover so I'm gonna move on to the next topic which is more on effects than nuclear weapons so just to give you the overview I'm if you guys haven't done any of the films of Hiroshima or whatever I would encourage you this or secular West to watch some of that stuff because it's it is very emotionally troubling but I think it's important to sort of get the full impact I particularly recommend there's a a film called Hiroshima Nagasaki August 1945 which is only 15 minutes long and it's based on film that both Japanese photographers and US Army photographers took in the aftermath of the bombings it's mostly you know horribly burned people and so on when I first saw it I was in high school actually there was a girl in our class who passed out part way through the film and so they had to stop the film so it was only later that I actually have a chance to watch it all the way through but any case it's it's an amazing level of devastation that can because this is what Hiroshima looks like after the detonation of what would be considered today a teeny tiny nuclear bomb all of the nuclear weapons currently in the u.s. stockpile some of them have adjustable yields but all of them have potential yields that they can provide they're much bigger ah then hiroshima you know a typical submarine-launched weapon today might have a yield of 475 kilotons compared to fifteen or sixteen kilotons and by the way anybody know how many nuclear weapons they're still physically exist in the United States even if they're not an active deployment at the moment roughly that's a pretty close on the actual operational stockpile is that the total amount is still of order nine to ten thousand nuclear weapons which is amazing if you think about it each one of those it's like way bigger than what obliterated this Japanese yeah they were sort of reinforced and designed for seismic you know survivor earthquakes and things like that and there were a couple of buildings pretty near the blast that actually survived this it's remarkable yeah basically if you increase the yield that the same effects pertain over a larger distance and let me just jump to that well let me let me do a couple other things first so this is a normal brick building not reinforced by steel or anything like that and this is the same building after five pounds per square inch of peak overpressure unfortunately for me from the point of view of a scientific person because all of this stuff all of this technology was originally written about in the United States in the 40s and 50s all of the units are non metric so kilotons are you know short tons and pounds equivalent and megatons and so on and all of them over pressure measurements are in pounds per square inch and you know it's just but this is an amazing photo of one of the early hydrogen bomb tests and what's amazing about this is these are destroyers and cruisers they were there were extra ones nobody's on us so they were just testing to see what the effects were well you can you can judge a plate like so here's the ball here's how big the ship is so it's looks to me like it's what 15 ship lengths all right so now we'll get some actual distances into this game hmm yeah that's so different all right so they're different kinds of effects they could kill you all right so I mentioned the firewall and it's inside the firewall is just completely vaporized all right so at one Killick at 1 kiloton square kilometers here so point zero 2 square cloggers not a huge area and it's covered you know substantially larger for ten kilotons not quite 10 times bigger and substantially larger again for 100 kilotons and if I move this line up a little bit you can see how these things scale exponentially with the deal so the radius at which you have a particular level of radiation if you have 10 times as much yield in your bomb will be 10 times 10 to the point nine one nine power the distance the blast radius scales as the third power and the thermal radius scales that's the point four power roughly yeah what since those are different they aren't all the same different things are the it's lethal for different levels of yield so early on at quite small levels of yield you will see that things like the radiation are actually quite important whereas when you get out higher you might find that the burns from the thermal radiation are much more important then the number of people are going to be killed from the prompt radiation so let me talk about each of these effects so you've got vaporization by the fireball then you've got this blast wave I mentioned that's going out from the explosion knocking everything down then you've got the what's called the prompt radiation that's the radiation emitted immediately by the blast so that's going to be neutrons and gamma rays some extent x-rays okay if you get 500 again somewhat bad you know rogon equivalent man that will kill roughly half the people who get that much radiation well and everybody gets that much radiation will feel really bad they'll be vomiting their hair will be falling out etc second-degree burns if you get them over most of your body it'll probably kill you but not necessarily depends on what kind of care you get and you've got to remember in a situation where these things are going off there aren't going to be enough hospital beds on the face of the planet to actually care for all the burned irradiated people even if it was one from a terrorist nuclear attack or something like that you know the local hospitals are going to be destroyed there's gonna be literally tens of thousands of burnt or maybe hundreds of thousands of burned people there aren't tens of thousands of burn beds in the entire United States so figuring out how to treat everybody is a huge so if you have the you have the fireball you have the plastic you have the prompt radiation you have the thermal radiation which is just it's very intense heat going off in all directions and one problem with this is if it gets up over a large area to say 10 per centimeter squared something like that then it tends to ignite things all over the place and you can have what's called a firestorm anybody know which cities in World War two experienced fire storms everybody knows that wow I'm impressed Dresden Dresden is one what's another Tokyo and what's another the other one was near Hiroshima Nagasaki interesting enough it was a cloudy day and they didn't have a fire started every second but they did it at Hiroshima so these fires water fires get set they're burning the temperature goes up they start setting more things on fire eventually it sort of coalesce --is into a huge as the name implies storm of fire and it starts using up all the air and air that hot air is rising up from the firestorm and it's sucking in all the air from outside you get these horrible winds coming in and it feeds on itself and it keeps burning until everything is burned basically almost the probability of survival if you're inside a firestorm is it's not zero but it's close to it and for the bigger bombs say for the 100 kiloton bomb you see that this thermal effect is much bigger because it it's yeah because it scales better and so you're much lot more likely to have fire storms from the big bombs than from the little bombs interestingly enough the US government in all this you know calculations about how many people would we kill on how much industry would be destroyed and so on with so many nuclear weapons they never included the fire effect because it was it was considered to be uncertain but in reality it's there's lots of ways to estimate it and it's probably at least the surface some of these other effects I mean the radiation effect it's highly uncertain because you know people are the buildings and you know shielded by various things and so on and there's a fascinating book of sort of bureaucrat history about why though why it was in the Air Force's interest and so on to ignore the fire effect it's called whole world on fire by woman they will in okay so the fireball is the instantaneous ball of gas coming out of this so you have this you have this huge quantity of energy in this tiny little ball of nuclear material which is now turn to a gas and then it goes and that creates this huge fireball and then that fireball is reading intense heat and so you really want to watch the video of a nuclear test at some point especially at Trinity or Priscilla actually it's one of my favorites but it's this amazing series of color of you know intense white initially and then you know yellow and orange and purple and red it just looks like hell incarnate in this in this swirling cloud of smoke and fire and put that intense heat that's radiating it out in every direction is setting things on fire all over the place you know newspaper wood people's clothing leaves you know gas mains well you know all sorts of gas lines would get broken as buildings fall down that gas is gonna catch on fire you know gas stations are gonna be exploding right and left and then all of those fires heat up other things around them and then coalescence into this sort of huge zone of fire work just things are burning and that's the firestorm okay if you read the first chapter and what the president needs to know about physics about 911 about the buildings that can move between towers is fire minus five psi overpressure what do you want to know about five psi is that I wish you would that just be five five additional pounds on what we experience now uh yeah it's a it's a shock wave so basically the air is compressed to a greater pressure than there now and it's and that compression front is moving and it's moving it you know more or less the speed of sound so it sort of comes over you and it might you know many people are killed by being blown into buildings for example or having you know big chunks picked up and and thrown at them it's like sort of an instantaneous tornado and then it's over and then actually there's a there's a bit of a wind coming back the other way after it goes past and that knocks stuff down and the reason most people aren't gonna actually be killed by five psi unless a building falls on them but almost everybody not almost everybody but a huge fraction the people who are within the radius where five psi exists will die because of one of these reasons and in fact I have a have a slug well not select hold on just a moment let's go to here if we can all right so this gets back to what we were talking about a moment ago about the quantities of material so I just wanted to show you that picture that that ball is the same size as the plutonium that's just glass but it's the same sizes and put them in for the Nuggets and I can call this is the fireball from the Trinity test you can see it really is basically a ball of fire kicks up a lot of dirt around the bottom this is this what's labeled a lock front is where that the shock wave that came down and bad stuff is starting to join with the shock waves it just came straight down and they're gonna move out like that this is the mushroom cloud so that the fireball did this big ball of fire but it's hot right so how do you rise it so it goes up and it starts spreading out then it starts cooling off and it comes out and one of the things is if you go close enough to the ground right you're gonna suck up a lot of dirt rock etc that's gonna be vaporizing that fireball it's gonna be pulled up into this giant mushroom cloud and that stuff is gonna get contaminated with those fission products from the nuclear bomb and that becomes intensely radioactive dust basically that's in this mushroom cloud then as the wind takes all that stuff all that dirt dust rock etc it starts falling out and you get radiation going you know all the way you know falling down and that's what's going to fall out so fall out basically doesn't happen unless you set up the bomb low enough that the fireball touches the ground they set off the bomb in the air as you did in Hiroshima Nagasaki got half fallout so we didn't really know about fallout very much until later and nuclear test program there was a most unfortunate Japanese fishing trawler that was to close down when to one of the early hydrogen bomb tests ironically named dragon if I remember correctly they've got a gigantic dose of radiation from the fallout from tests but this was the slide out I was thinking I would get to so we're the overpressure is greater than 12 pounds per square inch everybody got the first approximation in the range from 5 to 12 half the people died almost everybody's injured only a few were set from two pennants per square inch to 5 pounds per square inch not that many people died a whole bunch of people are injured some of the people are safe beyond that almost nobody does few people are injured most people are safe these deaths are they mostly due to other factors were just in fact overpressure is mostly due to other factors I mean in here this level of overpressure might tell you it might rupture your lungs or whatever but mostly it's you know things are falling on you everything is on fire the whole world is irradiated you know etc when during this zone you're gonna get killed nine different ways it's over determined problem that you're gonna be dead all right so I've talked about fishing weapons but we should spend at least a moment on fusion weapons and put this up at some point and use the blush I don't know we'll see but so thermonuclear weapons are it's a very interesting thing so we've talked about how you go out of energy out of splitting these big outs turns out you can get some energy out of putting the little ones together in particular hydrogen and it turns out it's pretty hard to put just straight hydrogen together it's easier to make off fuse if it's hydrogen that has an extra Neutron in it which is called deuterium so that's a a proton and a neutron in one nice or what's called tritium which is a proton and two Tron's in one new nucleus there all kinds of hydrogen there are isotopes remember this each element is defined by how many protons it's got they've all got one and then each isotope is defined by how many protons plus neutrons it's got so deuterium has two because do means two tritium tri means three so they've got three protons plus neutrons so what you do is but you've got if you want to put things together you've got to overcome this electrostatic repulsion right so it turns out that the way you do that is you have when you when things together really hard and in order to do that you've got to get them up to really intense temperature and pressure so how would you take some determined tritium and get it up to really really extreme temperature and pressure yeah you'd use a nuclear bomb exactly so the modern term a nuclear weapon is actually at a complex device that involves fishing and then fusion and then more fusion and then some more efficient so I'll see if I can go through this so we have our basic implosion bomb here okay only we've gotten more efficient than just the solid ball of plutonium that we had in the Nagasaki bomb turns out if you take make it a hollow ball then it isn't a critical mass and so you've crushed it down from quite aways and so there's much less chance of some strain you're on messing you up okay turns out here you can get much more efficiency out of the hollow ball then you can and then they have an additional interesting idea they said well gee I'm only I'm still only getting you know maybe half of my fissile material actually efficient what if I set off some fusion that would create a whole bunch of neutrons because knew the fusion reaction releases a lot of its energy and neutrons and that would fish in some more of my stuff than it would more efficient in addition to getting some energy out of the future and so they put some deuterium and tritium gas in the middle of this hollow thing so the explosives crush down the thing it causes a fission reaction that heats things up and creates this intense temperature and pressure we've been talking about the net causes fusion so that sense a shower of neutrons out which fishin's some more of that plutonium that you've got there so you have basically better yield out of this little ball of plutonium that you had and then so then we have this intense energy and in particular x-rays so then the x-rays go way out from this and the this is arranged in such a way that it basically focuses the x-rays on this and it's literally it's literally the pressure of light that crushes this thing so x-rays are just light at a very high frequency okay so it's the x-rays are operating like an unbelievable hammer on this thing it's an amazing thing you would think it's gotta be you know a piece of concrete or something to crush something no it's just light that's crushing this thing and heating it to unbelievable temperatures so it turned out that rather than having a bunch of gas for this part it was more convenient to have to get your tritium by splitting lithium so they have lithium six and they fish in the lithium in this system and that produces tritium which then fuses with the deuterium that it's chemically bonded with so you have fission fusion from the deuterium tritium then more efficient because of the neutrons from the deuterium tritium then that causes this to be crushed down which causes this secondary part to have more efficient which causes some more fusion and then you get a lot of fusion here actually and then you get the neutrons flying out and you usually have some uranium out here that then causes more fishing overall you end up with about half of the energy coming from fission typically and the other half coming from fusion yeah how I would imagine it would be substantially more difficult to fission lithium given that the lighter nuclei are less stable right so how they can they reliably I how to make it a reliable process I'm not going to go into that for two reasons one I'm forgetting to details and two even more important I'm forgetting which of the details are classified I should say by the way that I want to give this talk and people say oh my god you know I can't believe all of this material is out there and this was in the 90s and President Clinton's first Secretary of Energy who most of you have probably never heard of his Lord Larry had launched a huge openness initiative and people just assumed now it must be his fault and all this stuff is out there oh you know we should try her for treason and I had to go back and explain no in fact all this stuff has been on classified for decades for better for worse yeah I am being careful not to give you anything that is class but I do currently have nuclear weapons designed clearances but right the problem is the neutron reflector honey and the temp right good point um you don't really need a lot of fish in here what you need is for this stuff to sort of crush down so you don't really care whether it's your meaning to you get somewhat bigger yield if it's to 35 because it will fishing and so you'll get some energy out of that so the Russians we're sort of Kostas no object went for you know 90 percent u-235 and there are secondaries whereas we tended to go first or you know 30 40 percent you to 35 some like that our secondaries so the x-rays that are guys are bothering me Roy so the x-rays that are second class it's hard to figure out the x-rays that are created from the first fusion reaction or universe in the primary right those are what causes the fission of the lithium right right so basically you have a fission reaction providing the energy and the x-rays that crushes this stuff that causes the fusion reaction to take place if you want to boil it down that's what's happened so then Dan so the fusion reaction that goes on in the primary is simply there just further facilitate right so that's calling boosted fission that's a that's a very good question there's a limit to how much you can do with a pure efficient bomb because as you put more and more of that nuclear material that's harder to have the nuclear reaction not happen until you want it to happen so basically the most you can do with a pure fission bomb is something like 200 kilowatts at least that's the most the US government ever figured out how to do whereas with a hydrogen bomb it's unfortunately unlimited the largest nuclear weapon ever detonated had a yield of 60 megatons it was designed for a hundred megatons but they toned it down a little too cause you know less damage when they did it did the test but even so there were trees you know Tim's are tens of miles away that were blown down I think you can actually get a satellite photograph of the area where that took place and they're sort of us still so Kevin did it although it was pre high in the air it was it was a 70 test and this it's escapes my attention I'm sure one Joe I know Joe one was the first test yeah that was our name for students it was the Tsar bomb King bomb Tsar Bomba you're right because it's just how much material yeah but we're a fusion fuel line and then you could get more about okay but make it a thermonuclear bomb is very difficult basically thermonuclear bombs are possessed by only the United States Soviet Union or Russia now Britain France China India tested one there recently one of their top scientists who is involved in the tested actually that didn't work there's speculation that Israel may be able to do what I personally got it they probably can they probably do have boosted weapons boosting is not that hard to do but this whole complicated arrangement is it's very very difficult to do that's that's what made Sakharov famous as a scientist in the Soviet Union is he was the one who figured out how to do data in the 70 P before he became famous as a dissident alright so let's talk I'm gonna shift now to materials from bombs because the fundamental thing to understand about nuclear weapons is the hard part is making the nuclear materials alright ninety percent of the effort in the Manhattan Project went to making the nuclear materials the basic principle of a gun type bomb was worked out by one of the physicists and two of his graduate students in the summer before they all arrived in Los Alamos okay so I mean there are but there were a lot of manufacturing and engineering difficulties in begging to gun type uh but the basic idea was trivial and in fact for those of you with the physics bent this is an amazing part this is literally the lectures that they gave to the arriving physicists at in the Manhattan Project at Los Alamos saying okay this is how we're planning to make our nuclear bomb with them further elaboration on each lecture by the guy who gave the lectures it's an amazing fact that this is an unconstitutional by document to me it's certainly where I start if I work out I've got that bomb that the server's a service there's a service point right by the way the let me just mention another there another couple of books if your again if you have a technical a bit everything you want to know about the effect stuff is in here the effects of nuclear weapons it's a wonderful book you can get it on eBay that's an official US government document of course I have that volume and I have the boolean traffic right and there's a there's a whole that this exists believe it or not in PDF on the internet you can download this book I think maybe in your reading I'm not sure it's called the making of the atomic bomb and it's just it's told in a great it's like reading a novel and it gets the physics pretty much right without overwhelming people who don't know anything about physics and it brings the human stories home that holds a large story I have told is straight out of this book it's a great book I wrote this book we're gonna use the twilight of the bomb but we're noticing both the first war physics is what they're looking at well right okay and this I think you have any readings this is a special issue of the annals of the American Academy of political and social science which is about all about nuclear terrorism and there's a chapter in your narrative by me and a colleague of mine named Anthony wire about basically how hard is it for tears to actually make a nuclear bomb if they had to get their material which is probably useful for you so back to it the final point the hard part is making the nuclear material these nuclear materials don't exist in nature except that let me just interrupt for a second is there a point of junk to a point where they can have five minutes worth of a break yeah let's have a break right now so it turns out the Iranian you dig up out of the ground is only 0.7% uranium-235 which is near any of you want and the other near any name the other 99 plus percent is uranium 238 that's three more neutrons that 2:35 okay so then you got to figure out I've got these two things they're both uranium so chemically they're identical and I can't figure out how do I separate the one from the other so I get more of the uranium-235 and nearly all the techniques for doing that are based on the fact that they have very slightly different mass 238 units of mass versus 235 that's a mess so it's not a big difference it's about a 1% difference and we'll talk about all the various techniques that people thought of it plutonium basically doesn't exist in nature now does anyone know an exception to that statement no turns out but long ago you may you may remember that the the half-life of uranium 235 is three-quarters of a million years so billions of years ago there was more uranium-235 in the uranium than there is today and it turns out that billions of years ago in a place called Oklo in Africa there was a kind of uranium deposit that was concentrated enough that when water flute flowed into it and slowed down the neutrons which makes it actually easier for the neutrons to split it atom and I'll explain that in a minute huh it caused a natural nuclear reactor to happen and so it started generating all this heat and power underneath the ground in this uranium deposit but that boiled the water which then made the reaction stop so then the water condensed and came back in which made you actually go which then boiled the water and so it was a sort of pulse to reactor would go for a while stop go for a while stop and this went on for millions of years and created a lot of plutonium but the plutonium only has a half-life of 24,000 years so almost all that plutonium is gone but you're still detectable atoms of plutonium in that uranium deposit now here's another question who in this room what country ah good boom if I remember correctly another question who in this room has plutonium in there everyone correct from atmospheric nuclear testing all of us have plutonium in our body every human being on the face of this planet had pounds of plutonium in his or her body as a result of atmospheric disaster all right hey soon to make plutonium which doesn't exist in nature in any significant of us what are you gonna do is you're gonna take this uranium 238 the useless uranium you're digging up out of the ground you hit it with a neutron well you think oh she's something it was a neutron it's gonna be uranium 239 that doesn't do me any good so what happens is it's not stable as uranium 239 it kicks out an electron and then it kicks out another electron and it becomes plutonium 239 when it first kicks out an electron it's neptunium 239 and then it turns into green and so then what you've got is you've got a bunch what what you've been a radiating with neutrons is still mostly uranium and then it's also got some nasty radioactive fission product stuff in it and so then you have to figure out a way to chemically separate out that plutonium you've produced from all the rest of the radioactive nastiness that it's embedded right and that process is called reprocessing there are a few other isotopes that aren't near rhenium or plutonium that Canon principals support a explosive nuclear chain reaction they've never been used in nuclear weapons and they don't exist at any very substantial amounts and in actual separated form where you could use it and none of them occur in nature and all of them are really hard to produce and in particular way beyond the plausible capability of any terrorist group to produce them so the way I'll start off with mine at maturity the way we used to make highly richer and the whole world used to make either richer and it was with what's called gaseous diffusion so you have a gas of uranium turns out that the only chemical compound of uranium that is a gas at reasonable temperatures and pressures is uranium hexafluoride go figure so as a result we have to do all of this really nasty toxic stuffed with fluorine in order to do what we want with uranium if you're ever interested in sort of the waste and nastiness that's involved in in all these processes I commend to your attention a wonderful book of photography called and work in the fields of the bomb which is served inside the various nuclear facilities in the United States and it's really not a pretty story in any case so you would feed a stream of this gas in and you'd have a barrier of a sort of a membrane that has teeny tiny little holes in it gazillions of them and the atoms that are moving faster which are on the lighter atoms are more likely to get through the barrier than the atoms that are not moving so fast and but there's only like a 1% difference so you got to put it through the barrier again and again and again and again and again and again so you need thousands of these banks and you need huge buildings with huge quantities of power they they used to use inside this building that used to use bicycles to get you know back and forth down the cascade hall where these gaseous diffusion stages were and at one time during the Manhattan Project they were using about 10% of the energy supply of the United States so it's it's a very energy intensive process so believe it or not the United States is still using a gaseous diffusion for its commercial enrichment decades later and so it's France but both of us are planning to replace that with the new dramatically more efficient technology which is the uranium enrichment centrifuge which now dominates the world of uranium enrichment but it's still the case you've got to do it again and again and again and again and again got a hook it all together appropriately in the room to get any substantial amount of enrichment going but it's dramatically more efficient then you mania min Richmond that means then gaseous diffusion as an approach to enrichments factor of 100 or so not more efficient but it's quite technologically demanding to figure out how to do it if particular if you look at Iran's program Iran other than Israel has the most advanced indigenous science and technology base in the Middle East they you know they have a lot of physicists a lot of Engineers etc they had to complete designs for harness tons centrifuge program from this black market network led by Pakistan's AQ Khan which also supplied Libya these are the Libyan centrifuges after they'd been transported in the United States this is the u.s. garden for international laboratory actually is probably a y12 facility right next to the laboratory but they said they had the complete designs in 1987 they didn't really get a whole cascade working and enriching uranium until 20 years later so this is a this is a challenging and difficult technology an obvious question is North Korea did get centrifuges from the AQ Khan Network but can they make them work and can they build more of their own alright personally I'm deeply skeptical they will be able to so centrifuge is a tricky technology what you're doing is you're spinning at extremely high speed sorry this this outer wall is going in more or less the speed of sound okay and that means you have to have a an amazing bearing at the bottom in order to avoid thing you know eroded away and you have to have it balanced incredibly fine line in the early days of the u.s. program the workers used to call these explosives own self disassembly machines because if they get a little bit unbalanced they shakes themselves apart and literally chunks of Steel go flying around the room at the speed of sound roughly which is not a lot of fun if you're working in that room and you also meet in order to be able to stay together at those really high rotation speeds you need really strong material but you need it to be really light material cos you're worried about your barrier a lot okay so they started off with aluminum that's not strong enough to do really good enrichment so then they graduated to a specialty kind of steel that you will often read about in the literature of that you know countries trying to get new come up with sandstone it's called meriting steel em ARA g ing and then the really sophisticated ones are now made out of carbon fiber okay and basically the idea is that the lighter stuff tends that it is easier to change its course to sort of turn it as the thing is spinning and so the heavier stuff tends to get flung more toward the wall and then long ago a gun in your house if you've managed to come up with a great idea for putting in some scoops that caused it to go up and down as well which turns out to make it much more efficient and you take me this stuff that has more u-235 off of the top and you take the stuff that has less u-235 off of the bottom and then it goes around to other centrifuges in the what's called a cascade of centrifuges so this is President Ahmadinejad walking amongst the centrifuges at Natanz these little ridges here are cooling things for the century the the thing you can see isn't actually the thing that spins the thing that spins is inside the thing you can see and these are some of the u.s. accentuated the u.s. centrifuges are really sort of extreme there may be two storeys tall whereas Russian centrifuges they Russians decided to go for lots of little ones their features are like this big you need to hook them up in cascades of hundreds or thousands of these centrifuges and one important thing to know is it's a very nonlinear process it's not like you know going from 4% to 10% is the same as going from you know 94% to 100% turns out going from the 0.7% you dig up out of the ground to four or five percent they use in a normal nuclear reactor is about three-quarters of the work of going all the way to the 90% that you want for a nuclear bomb so let me talk a little bit about those percentages a little bit because I realize I failed to do that earlier I think I have that later in the talk so maybe I'll wait and do that later so if you have a stock of low enriched uranium available to put in as your feet into your enrichment plant then you can make highly enriched uranium for a bomb much faster more or less four times as fast as if you're just going from that to area so that's why over the course of the last couple of years there's been this big hullabaloo over how much low-enriched uranium does Iran have and doesn't have enough that ah it could then re enrich that to weapon-grade to make to have enough ATU for a bomb highly enriched uranium for a bomb and can we negotiate with them a deal where they would export their loan rich rhenium as they've produced it and keep it outside their countries that they would never be a time when they had enough that they could reinvent to make a bomb because if that's true then you can multiply by for the sort of breakout time that they would require to make highly enriched uranium for above on the other hand I personally am of the view that it's very unlikely that if I'm Iran and make a bomb I'm gonna do it with the known material at the known facility that you know about because that facility will seems to exist shortly after everybody knows that I'm starting to make Colin rich you're in it because somebody will destroy so I think they would do it at the covert for somebody and one of the problems with centrifuges is they're they're little and they're easy to hide so a facility capable of making a bombs worth of uranium in a year would fit in the basement of this building there's a lot of the links in any normal country that are as big as this building how the heck do you find out it's a hard problem but the good news is enrichment is difficult I mentioned this Iran history this is some of the components of something somewhat more advanced centrifuges that Iran is working on they involve a wide variety of specialty components on the balancing thing let me tell you an interesting story there's that a guy at the International Atomic Energy Agency who's a one of their only centrifuge experts that's amazing they only have three or four centrifuge experts said you know this agency that's supposed to be safeguarding the whole world but he said when he went to see the Libyan subterfuges in Libya he said the first thing I did when I saw these rotors that they were going to use for centrifuges as I grabbed each of them with my hand and because there's enough grease on my hand that they will never again be able to use that for a centrifuge there's no way they can get it clean enough that it won't spin itself apart just from the all right so there are other enrichment technologies there's what are called calutron so anybody know what calutron means it's red right it's the University of California magnetron magnetron being something that essentially bins charged particles so what you do there is you take uranium you strip off the electrons by heating it up for whatever and you so you have this this beam of charged uranium part of materia mountains okay positively charged you put them through a big magnetic field with huge magnets okay and that the ones that are lighter are easier to bend and so you end up with the beam diverging into two beams one that has more u-235 them and the beams actually overlap a good bit so you have to you know do it again and again but that not too bad but it uses I mean if you thought gaseous diffusion was bad in terms of how much energy it uses this is really bad and so United States like companies gonna do that we did it ourselves during the World War two but you know as soon as we developed something else with her that was going to death so that technology was completely unclassified so in rocks I don't let's do that you know we don't care how much energy we're gonna use if we get the bomb so we don't say said no I didn't by the way many of you may not realize it while rock had no noticeable nuclear weapons program before the 2003 war they really did did have a big hope the rebels burn out before the Banshee 91 war there was a time when that was true it just wasn't true so you can also use lasers to you can actually tune lasers so that the energy it requires to strip the electrons off of a 235 atomism different than the energy required to strip it off of a 238 out of your actually tuned lasers so precisely that you can sort of preferentially strip them off the one and out the other and there are variety of other techniques that people have as vinegar with use this by the way and it is one of the cons from the rock after we bombed an asura uh you know I forget where the couch and not another article remember Mia I think all right so then there's plutonium this is the North Korean plutonium production reactor as I mentioned the first step is you radiate uranium so you've got to have you're gonna build a nuclear reactor nuclear reactor can be a pretty simple thing so big blocks of graphite gotta have really pure graphite so it doesn't absorb too many neutrons you put natural you're a minute in say rods like this you have some maybe gas or water going through so that keep things cool and you put enough of those that uranium in there and nuclear reaction starts happening you have some control rods so it doesn't go too fast control rods are things that absorb neutrons you can lower them down in and pull them pull them out and you're making your making and so that's the reactor in North Korea beyond then you take these fuel elements that the jung-hyun reactor they literally are about lucky a and you reprocess them so the typical way that was developed in the United States during World War two and it's used all over the world to this day it's called pure X but it's basically you dump up you chop him into pieces dump the pieces into boiling nitric acid you contact the nitric acid with some organic solvent and draw off some of them materials and do that two or three times and you end up separating one stream of plutonium one stream of uranium and one stream of the nasty fission products yeah and so the nasty fission products are the green goo and the barrels that's what that's supposed to represent it doesn't actually look the way it doesn't move how one generates we're gonna do that in a minute okay if we get there all right so this is actually uh he's significantly technically easier to do than the enrichment especially the centrifuge enrichment but it usually involves large detectable facility not always that people are starting to get better at hiding things so this is just sort of a schematic of that North Korean reactor so you have these graphite blocks you have these uranium fuel elements you have these control rods that absorb neutrons that can go up and down and these are actually these actually are not the control rods these are the fuel loading tubes but you do have control rods which don't seem to be labeled here exactly so then that there's a bunch of heat coming off of this from all the you know efficient taking place so you've got a gas that flows through and that gets heated up hot gas goes over here there's a turbine in this schematic there isn't any terminate young beyond you know the North Korean said this reactors for making electricity there's no there's no turbine there's no you know electrical wires there's no no it's a reactor was never done reactor was intended make blue time this is the reprocessing plant in North Korea again pretty large observable facility all right so let's let's actually skip that for a moment and see if I can get to the thing about making electricity deleted that slot alright so I'll go back to the where we were so how do you make electricity basically you have a reactor a nuclear reactor that's generating this nuclear chain reaction but instead of having it growing and growing and growing and growing and growing explosively you absorb some of the neutrons so that it's just staying at a steady state okay it's generating energy but it's not greatly increasing in the rate at which the chain reaction is happening so rather than being subcritical that is the reaction is dying down or supercritical which means the reaction is growing and growing and growing and growing exponentially it's just critical it just stays flat and of course the key to nuclear safety is making sure that stays true and so you have these control rods that absorb neutrons and you move them in and out and then the typical reactor that exists and for most of the power reactors in the world are what are called light water reactors light water is the word for what we ordinary people refer to as water the water that comes out of your tap is light water what that means is it doesn't have that second nucleon in the hydrogen it doesn't have a neutron along with the proton and the hydrogen it's just a hydrogen is that in h2o is just a proton so the reason that there's water there it turns out it's a little bit of a surprising thing you would think in principle that if a neutron was going really fast it would give that out of a good whack and that would really be the best thing for splitting the atom turns out that's not true turns out as much easier to split an atom with a slow-moving neutron then with a fast-moving Neutron why is that so it's because of this this strong nuclear force and the weak nuclear force so if you imagine the atom is sitting here and if a neutron that's going really fast it has to hit it right on in order to hit it at all if it's going past it it's just going to and then the strong nuclear force isn't going to be able to reach out and grab it whereas if the proton is just sort of you know enduring around then there's much more probability that the the strong nuclear force will go in but then it will pull it in and it will hit the atom and cause at least some of the time to occur so is the disease fact that it's split come from the actual impact of the neutron their lack of stability of the new nucleus mainly right so what happens in a reactor where you have this water the water is the coolant but the water is also what's called a moderator but it does it slows down the neutrons the neutrons go out of the atom they're going pretty flippin out of the fishing they're going pretty fast and then they go back and they hit all this water Blanc around and they get slowed down and then when they happen to go back toward the where the fuel is again then they're slowed and they have much more a better chance of splitting something if they hit and that's why instead of needing ninety percent or something like that like you would have in a bomb you only need maybe four or five percent of the uranium to be the uranium-235 okay now if you go for heavy water which already has Neutron with the proton in each atom of hydrogen rather than the light water then you can use natural uranium because the water isn't absorbing neutrons hardly absorbs neutrons every once in while you make a little bit actually so yeah and similarly in a graphite reactor the graphite if you'd make it really pure nice what's called nuclear grade graphite doesn't absorb it so you can use natural uranium you don't have to bother to enrich it remember mitching is hard so if you want to do something simple you're gonna go for one of these for your plutonium production reactor but some people do use these for power reactors as well Chernobyl is a graphite reactor for example there are still reactors operate well there were reactors until very recently operating in Russia that were the generation of reactor that they learned a lot of lessons from in order to design the Chernobyl reactor fortunately those were plutonium production reactors and they've now been shut down as part of a US and the lunar program yeah somebody had a question back there so then right yeah so could you for the the heavy water in the graphite reactors did you literally well you get you got a do you know Milla didn't concentrate it and make an indefensible fuel all of us on do all those kinds of next we don't have temperature developing the fast Neutron reactor is not important in the world today but it may be important in the world in the future this is what's what people refer to as a breeder reactor because it makes more fuel than it uses it may sound like a perpetual motion machine it's not it's just taking u-238 and making it into plutonium so you need some plutonium to get it started but then it makes then you after that you just add more u-238 which you've got a lot of and it keeps making plutonium and so if you're worried that we're gonna world is going to run out of uranium and we're gonna need lots of nuclear power then you start thinking okay we're gonna need these breeder reactors in fact the world has your juju out of uranium there's no bug you need to worry about bigger reactors for life now there's obvious a lot of problems with reactors that produce lots of lutonium alright so some terms to remember about all that highly enriched uranium is anything with 20% or more u-235 I know lots on the last table what's that's we're just getting to death okay so that's as opposed to natural uranium which as we learned with 0.7% we're low enriched uranium which is typically four to five percent can be up to you know there are things that are fueled with 19.9% so it won't count aside or depleted uranium which is what you get the waste from enriching uranium is stuff that has less than then there's uranium that is referred to as weapons-grade means it's 90 percent or more so that's what you would prefer to have for a nuclear bomb but you don't need that much for a nuclear bomb bombs can be made with material far below weapons-grade the Hiroshima bomb as I mentioned was an eighty percent weapons-grade plutonium similarly is plutonium with about 90% of the that first thing you make when you hit you 238 atom with one neutron you to pu-239 plutonium-239 but then if you leave your stuff in there for a while eventually some of the items are going to get hit with another Neutron and that will be plutonium-240 and then some of them will get in with another neutron that will be plutonium-240 one and so on so reactor-grade plutonium if you're making weapons plutonium because you want a lot of plutonium-239 to take your stuff out after it's been irradiated for a fairly short time if you want to make power you don't want to be refueling all the time so you leave it in for longer to have more more power production and less time spent refueling and so you end up with more of these less desirable isotopes the 2240 the plutonium 241 and that ends up being called reactor-grade plutonium but unfortunately you can make above for a reactor plutonium and in fact you can make reliable and effective both start me after good cutting this is just showing mcgucket before you go on let me just see if we can get to a comment of sensibility about something um we have this class that's for 6:30 we certainly don't expect you to go all right but beyond I thought it was only until 5:00 I know that's accurate that's what I'm saying I can know where time I'm just thinking we have some flexibility we're roughing I didn't know what you had any flexibility in your time and the student said any flexibility in their life what's your max out quarter oh no I don't think I have a definite thing I have a I have a babysitter who's expecting me to be home at sex but if I'm 15 minutes later I don't think it'll be a huge deal all right so I mean I just want you just to pace ourselves in terms of questions in the book or this is complicated stuff right over here's a lid over the necessarily those of you were obliged to go someplace else we're videotaping this but we could spend another 15 minutes with you it would be very valuable right I'm gonna skip over the details on the fact that you can make bombs with the reactor-grade stuff in an interest of time so what are the hard parts here what are the things that are difficult for countries or for terrorist groups over there the number one hard part as I mentioned is making the weapons usable nuclear material whether it's highly enriched uranium or whether it's a battalion that was about 90 percent of the effort programs the second hard part if you're a state is making a good nuclear bomb a nuclear bomb it's safe that's reliable that you've know what the yield is and it can be put on a missile because if you want to put it on a missile you know your missile doesn't have infinite lifting capacity so you want it to be little and it has to be able to withstand the unbelievable sort of you know acceleration and shaking and so on that goes involved in being at the top much much harder job for a state to make one of those safe efficient reliable weapons than it is for a terrorist to make something that you know has some good chance of going off and causing a lot of damage but it is unreliable and unsafe and well you know it requires a fairly large truck to carry it around and so on unfortunate so that's so it is in my view it is simultaneously true that it is quite difficult for states to get nuclear weapons and yet that there is a significant risk that terrorists can get nuclear weapons even despite the much lower technical financial institution already rest's because states are trying to make the nuclear material themselves terrorists would probably rely on stolen nuclear material and then the very very crude nuclear bomb so they'd be trying to short-circuit both of these really difficult parts and they wouldn't even be bothering thinking about designing of making a hydrogen bomb so these are really the three really hard parts the crude bomb if you've already got the material most states could do and plausibly even some particularly well organized terrorist groups though there are a number of challenges and actually machining highly enriched uranium or plutonium making the conch let's be you know the shape you want them to be etc so let me just mention a few things about nuclear terrorism because I think this is a real danger first of all Paul Cota has been actively seeking nuclear weapons and there's at least some suggestive indicators that suggests that they may still be doing so this is a sketch from a seized up kind of document from Afghanistan this particular bubble can work it looks like they're making a gun time bomb out of lieutenant in there but there is more sophisticated work that al-qaeda did including I got to the point of actually carrying out some tests of conventional explosives for their nuclear bomb program in the desert in Afghanistan they have also considered sabotage and nuclear reactors which could create a nasty mess over a fairly large area if it was a very successful sabotage it's not easy to sabotage a nuclear reactors because all the safety mechanisms that are in place make it very difficult to to make all those safety things fail at the same time in order to get stuff over this country it's not impossible and dirty bombs are probably more likely but would be far less threatening a dirty bomb is if you take some radioactive material like you might find in a hospital or industrial site or whatever and use explosives or race other means to just spread it over the surrounding area to just create a mess and create panic and chaos itself so as as we mentioned before the gun tank bomb really is fairly simple as plausibly with indicate the sophisticated group an implosion bomb would be more difficult but it's still conceivable one thing should probably shouldn't say any more than this but it doesn't have to be as complicated as what we did at Nagasaki there are a variety of simpler ways to do it so this is from an official US government assessment basically says a small group of people none of whom had access to the classified literature could plausibly design and build a crude nuclear device they wouldn't need any special equipment that would raise eyebrows they'd need basically a machine shop type facility and this gets back to what I said about looking for needles in haystacks this is a guy by the name of Sergeant her Blair in that box that he's carrying in one hand with his t-shirt in his dirty chinos he's got the plutonium for the first-ever nuclear bomb for the Trinity test it's pretty hard to keep people from smuggling something that small and hard to find out you see he has no special equipment for carrying that around one of the during the break what somebody was asking well how radioactive is this stuff the highly enriched uranium is hardly radioactive at all in the Chinese nuclear weapons program in the early days they were manufacturing the actual components and the nuclear weapons by hand with no you know special equipment or anything we bothered with some special equipment because we cared a little bit more about the people doing the manufacturing but yeah you can't do that plutonium is more radioactive than highly enriched uranium you definitely don't want to breathe plutonium if you can avoid it but you can carry this stuff around without any special equipment it's also quite hard to detect a lot of these radiation detectors that we're installing at borders are not going to detect a lot of the stuff that we wanted today well tell them they're almost early to tell highly enriched uranium if it's metal and it's got any noticeable shielding and around it I'm not going to be detected but almost all the detectors were putting on alright and that is the end of my slides I can do more on nuclear power if you're interested on nuclear power but we only have seven more minutes of the allotted time we will bring you back so we've got is that more or less what people wanted to know I just have a question about the gun type and the emotion type the gun type as you said earlier takes uranium Wow can use uranium and plutonium correct but Exodia is the one that's more likely to be smuggled because of the size that's no observation Lee that doesn't tend to be true the cases that we know by the way there are many real cases of real theft and smuggling of real highly enriched uranium and plutonium there's 18 cases on the IAEA is less that involved after a loss of actual highly enriched uranium or plutonium there are several other cases that we know for sure happened but they aren't you know the relevant person you know confessed was convicted spent time in jail blah blah blah but for some reason they're on the II's list because the relevant state hasn't been willing to confirm it tonight so anyway there's more than 18 cases of that have taken place and most of those are highly enriched training they're only a few that are put telling cases you know it's yes it's hard to just bubble you know my sutures were bald it we've gotta hold in your hands but it's not that much harder well my question is a petard a terrorist group is more likely to use the gun type because of technical there was it if they could get that and return him they would certainly prefer that yes so it would be more likely be of use uranium if they could get it correct that there may be a correlation between that and the fact that most of the cases we've seen a bit on imagery however one of the interesting things is none of the cases we've seen so far have actually involved you know clear buyers they've been not only not organized crime but what I like to call comically disorganized crime there are people who stole stuff and had absolutely no idea how to market it and I can tell you some highly entertaining stories if we have time but what are these questions is there a selection bias there are we not seeing the people who are really kind and know what they're doing and have a buyer isn't only the incompetent people are gonna cut yeah how easy ways to take the plutonium uranium I'm curious as to what the policy is now and what Russia's doing to fix that and all that I'm curious as to what the US does to great questions the subject I could go on for for further hours or perhaps days um we will right at that particular facility things are very much better they are not perfect fighting means but first of all each of these 80,000 discs that has a barcode on it that are individually you know number so you know is this you know is this number 1840 to missing or not secondly they're all sitting in a vault and it's it's a big impressive steel door of all I can tell you I've been there I've been into that ball and what's more they have nuclear material detectors you know in all hallways leading to that involved so alarms would go off if anybody we're carrying out stuff from that vault and they have a fence around that building and this stuff it doesn't come out of that involve except when it's in use and it isn't left out on the table at night anymore thought and overall in Russia I would say things the difference between 1994 and today is like night to day it's just dramatically dramatically better I still have a lot of concerns Russia has the world's largest nuclear stockpiles in the world's largest number of buildings and bunkers and they have security that still has some noticeable weaknesses and they have massive corruption and theft of everything that's not nailed down in Russia actually had a fascinating conversation with a retired general who had been the commander of the force that guards all of Russia's nuclear weapons and I asked him after Mia chatted about various and established a rapport you know are you worried that the corruption in the Russian military is going to penetrate this force that guards the nuclear weapons which is called the 12th gulag that's a Russian acronym and I just he laughed and said well you know in the 12th we have three men rule which means you can only be with a nuclear weapon if there are three people there so most generals prefer to work with conventional weapons were there more opportunities to make money so this is about security leaks of a different type but you said you know a lot of classified information curious about the process by which you determine the government determines what information is classified and what is it this is this is one of the most deeply messed up aspects of policy that exists is the hole in the institutions of secrecy in this country are profoundly broken my there's all sorts of stuff that is classified that has absolutely no reason to be classified except that it would be mildly embarrassing to somebody different we're reveal and there's all sorts of stuff that ain't classified that and why do you probably oughta because what's more every country does it differently so you know what there are things that are highly classified here that are unclassified in Russia there's a much larger set of things that are unclassified here that are completely classified in Russia so you know a smart bad guy pulling together stuff from several different countries would be able to pull together more than any country and what's comfortable with and those of us who write about things like nuclear terrorism constantly have to be deciding what can we say in order to motivate democracies to action without giving bad guys ideas and everybody draws that line in a different place so again an intelligent bad guy pulling together what everybody is saying would be able to pull together more than any one of us writing about these things comfortable I've combination there is there is a document that's sort of which is called the classification guide and there are actually different classification guides for different aspects of this technology that will say you know this is classified this general subject as long as you don't say this this and that is unclassified etc those classification guides as you might guess in and of themselves are classified yeah my name is Daniel I was just wondering um once a group of people at state or foreign terrorist organization or whatever gets enough fissile material by whatever means how long would it take to actually build a working bomb even like just regular huh this is a again a fascinating subject and one of great debate it depends on the form of the material that they get so there there are certain kinds of highly like have enriched uranium from a research reactor for example there's a lot of research reactors you know demonstrated MIT there's a research reactor with twelve and a half kilos of 90% enriched ACU and its core however now at 12 kilos of 90% of risk HEU is in it sort of bonded with aluminum you'd have to do some chemical processing on it it's extremely radioactive you know there's some other steps you'd have to do before you add island which mean even if you could get it out there's this huge lid on top of the reactor and you'd have to use a special tool to pull it up out of it Goren so it depends but I will say there are certain facilities in the United States where the regulations specify that you have to build your defense for that facility so that the bad guys can't even get into the building because of concern that they might be able to set off a nuclear explosion while they're still in the building and I won't say any more about the basis for that concern Oh my name is Camila by the way and I was wondering if you to talk a little bit about how to turn reactor grade material into weapons tell people uh you don't turn the one into the other you just use the reactor grade material for a bomb so you make a bomb with material that is not weapon grid weapon grid is what weapon designers prefer it's not what weapon designers need but it's harder to turn reactor-grade unfortunately not significantly so there are issues and problems but it doesn't take any more technology so let's imagine you had the Nagasaki to Sun and you have just made exactly the same thing only you use reactor-grade plutonium rather than weapon grateful time don't do anything different might put the bomb together just before you're going to use it because the reactor plutonium gives off a lot of heat it's gonna eat up your conventional explosives a feeling that sitting in there for a long time that would give you an assured reliable yield of hundreds of tons it would not give you you have some chance of getting a bigger yield than that but the reason it would only be hundreds of tons rather than 20 kilotons as Nagasaki was is because there's so many neutrons from the plutonium-240 that it would almost assuredly start the nuclear chain reaction off way earlier that you wanted it to so that's but there are also there are nuclear weapon designs that the United States is used that are immune to that problem that the nuclear material isn't in a form that's critical until the time when you want it to go off so no matter how many neutrons there are they can't start off the reaction before you want it to start so they're there so those you know you could use your but Tony basically without a major problem there is a heat issue as well you have to figure out ways to manage the heat but as I mentioned a lot of the early u.s. nuclear weapons were made with insertable nuclear components where you didn't even put the plutonium in you know until you were about to use the bomb so you know you keep this heat generating reactor-grade plutonium compliment in a fridge or whatever and then you put it right in your book yeah my name is Vijay thirty years ago we read about how long center features seasoned centrifuges was a woman effective for using bad centrifuges was technical aspects of it the expertise and nowadays we're hearing about the yellowcake from Nigeria possibly and aluminum tubes in our war my question is does the International and proliferation community has some kind of handle I'm not just where this material is but who has the knowledge to make this material another makes you contact Figueroa bread this is again a fascinating and hotly debated topic there are those including myself who think despite all the damage that AQ Khan and his black market Network did marketing this technology all of the world basically they marketed it to at least as far as we know Libya Iran Iraq and North Korea nice set of countries to be selling nuclear rockets technology to and certainly al-qaeda also you know made contacts with them as far as we knew there wasn't any actual cooperation that resulted but in any case there are those like myself who think there are still horses in the barn that it's still very difficult to make centrifuges that they're stole a lot we can do to control centrifuge technology there are other well important people who say no horses are out of the barn any country that wants to make centrifuges at this point is going to be able to make centrifuges I would argue the history of the Iranian program tends to lean in the opposite direction since its taking them so long to get there well it was also the bomb wasn't drafted you know exactly the optimal point in the city but yes weather has a big effect on the thermal effects and how far you'll have a fire obviously you know if it's foggy it's if it's foggy you're not gonna have you know thermal stuff going out far enough to cause fires at the same distance as if it's a clear blue sky yeah one of the readings you're forgiven once you used your name or sufficient reading so I haven't read myself by the right so like the tested detonated life in Central Park Central Park is well first of all nobody in their right mind if they had such a device would detonated in some place where they're only wiping out a park so I did a I did a rough estimate of a ten kiloton terrorist nuclear bomb detonated at Grand Central Station on a typical workday and again I didn't use all the complicated software and stuff that you can get for this kind of stuff yeah the sort of rough estimate was half a million killed and about a trillion in direct economic damage that it's just the value of the buildings and lives destroyed and the economic activity of them that would otherwise have going on in those particular places and then you add on to that you know what would happen to the stock market and global trade and bubble line you're talking you know multiple trillions fires the shockwave right you would on a typical day the wind is blowing north and Manhattan which probably means you'd have to evacuate all of Manhattan because of the fallout and you know it's likely you wouldn't be able to use Manhattan you know the vast majority of that happen for many years to come so that's a that's a big headache can I have a quick kind of magic but even more important in a way I think would be the psychological and political effects I mean if you think the u.s. foreign policy has been violent and annoying since 9/11 wait to see what happens after it's a whole city goes up in smoke and in terms of civil liberties when people realize you know oh my god that came from a ball and material this big you can forget about limits on searches and seizure and in terms of foreign policy I mean you know the very notion of sort of state sovereignty over control of these materials I think might very well go out the window after something like that or at least the United States might seek to have it go out the window and the other thing is somebody whether the guys who did it or somebody else is gonna call up and say I've got five more and they're already hidden in US cities I'm gonna start setting them off unless you do XY and Z who knows if that's true or not but boy they'll have some serious credibility after that first one that's going off people and they're gonna make that threat public people will start fleeing major cities we have very limited ability to support all those people on the country side I mean the prospect for utter chaos is quite frightening which is why and my new focus has to be on prevention unlocking down the stuff Reed securing above you will I know it's very difficult nobody nobody knows the answer to that question in that analyst book I have a mathematical model trying to assess the answer to that question I say you know this model doesn't give you the answer because all of the input parameters are fundamentally unknown however here are some plausible just as an example of how to use the model here are some plausible input numbers which came out to 29% probability over 10 years to which everybody immediately said Oh bumps us the probability is exactly 29 percent that's not what I said I said here's an example these are vaguely plausible input parameters but you really don't know what the input parameters are could be could be 1% could be 50% Graham Allison has been of the view that it's it's 50% or greater I think that might just purely guessing everybody's guessing I think that's too high I think it's lower than it used to be in my view we got a lot of nuclear material in a lot of places that is a lot better security than it used to be there's dozens of places in the world where there just isn't any high enrich uranium or plutonium anymore we've airlifted that stuff out that represents in a real sense bombs that will never go off and al-qaeda is profoundly disrupted compared to what it was before 9/11 we've you know locked up or killed a large fraction of their top leadership and I don't think the sort of leaderless jihad types that can do a truck bomb here and a truck bomb there take down an airline or whatever those people are never gonna be able to do a nuclear bomb this requires you know a serious focused organization like al-qaeda central it used to be to have any hope of being able to do it and even even then you know it's it's a big challenge for a terrorist group I think it's big enough to worry about but not big enough to be terrified I liken it to let me just say one more thing before I take your question nobody in their right mind would operate a nuclear power plant upwind of a major city if it had 100 chance of blowing with Scott hi every year because everybody would understand that while 100 is not that big it's way too big to take that rest I personally think we're running probably a somewhat larger risk than that from the way we manage nuclear material around the world today my question was about the North Korean sort of weapons program so if my understanding is correct logistic way it's a lot easier to make the gun type correct so the North Koreans have to go for the implosion type phrase they doing plutonium right and I'm right and I guess my question is it's not immediately apparent to me why getting weapons-grade plutonium is easier than getting weapons-grade uranium considering the different economic constraints of reprocessing and that you I guess don't need us as enriched uranium to sort of facilitate the atonium production process but I mean if you could maybe outline why flitter item is the more and also given the difficulty of making Russian bomb compared to well technically making on making a nuclear chain reaction go in enough to make some plutonium is actually really a very straightforward thing to do and it's it's trickier if you want it to be safe huh but the way the North Koreans operated their reactor and particularly their spent fuel was just horrifying not to put too fine a point on it I had a wonderful meeting over the course of a couple of days with the guys who when it can to the North Koreans spent fuel on the 90s and one of them said you know if an OSHA inspector had been there when we were doing what we were doing he woulda keeled over and died when the u.s. experts arrived for the North Korean spent fuel pool literally you could take a stick and put it into the put it into the fuel pool and you couldn't see the end of the stick if it was this far into the pool I mean the pool was filled with mud you know there were dead things floating in it I mean it was it was turns anyway be that as it may so it is just technically simpler to do even though you have to be the reprocessing as well as the reactor in the reprocessing Note cost some money again it's pretty technically simple if if you don't care about hiding it and you don't care about it being especially safe you know it's chemistry that's been unclassified for decades the design of the reactor was one the North Korean the British it's been but I think would be easier to go with the plutonium bomb if you were worried about the sort of level of technical expertise you were being able to pull together you would go for the plutonium bomb I think and it's an interesting fact that in the 70s you will see all of the writing about nuclear proliferation basically says but tell me input tell you plutonium plutonium plutonium uranium enrichment is really hard we're worried about the plutonium and then you know AQ Khan stole the centrifuge documents from your n Co in the 70s and made you know made centrifuges in Pakistan you know which was one of the most technologically backward countries in the world and everybody said oh I wasn't expecting that to happen and then you see in the proliferation literature of the last 15 years or so you know plutonium is a problem but you know uranium is a big problem too and actually I would say right now people are more worried about uranium partly because you know all of this technology from the Khan Network is just out there I mean you know so he was that network was marketing not only the designs but these detailed manufacturing manuals that are you know good enough that you can plug them into a computer-aided manufacturing machine which now you can do in pretty much any country in the world and you don't make centrifuge components and those things were on the hard drives of Grist unaccountable middlemen you know the Tanners and Switzerland and various other people and if one has to guess one has to guess that those are still out there somewhere and they're gonna you know show up in and additional countries in the future so there that's the basis for some people saying cats out of the bag we have to worry about convincing countries that they don't want nuclear weapons rather than even bothering with it what's called the supply side rather than the demand side of nuclear proliferation I don't believe that trip that's true I believe there's still a lot to do on controlling the supply of this technology but we do have everything you do I'm controlling the supply the technology is a delaying tactic unless you can convince countries that they don't want nuclear weapons you're the spread will ultimately have if you have to determine country that remains determined over a long period of time they're gonna get nuclear weapons eventually but the reality is the vast majority countries don't want nuclear weapons it's an amazing situation it's the first time in human history where the most powerful weapon available to our species has been so widely forsworn we have every country on Earth other than not the nine countries that have nuclear weapons has a treaty commitment not to get nuclear weapons that they have entered into freely and all but a couple of those are abiding by that treaty commitment it really is is quite a remarkable thing for the vast majority of countries they understand that nuclear weapons are irrelevant to their security situation or would make things worse rather than better and we've got a we got to work on that making sure that stays true and actually reducing the demand has worked a lot better than than people realize there are today many more countries that started nuclear weapons programs and gave them up then there are countries with nuclear weapons so that means that our efforts to convince them that they don't want to clear weapons succeed more often than they fail even in the cases of countries that start a nuclear weapons program which is a minority of countries in the first place so there's reason for hope [Applause]

Channel: Ronald Veisenberger

Views: 67,056

Rating: 4.7582736 out of 5

Keywords: Nuclear, nuclear weapon, fission bomb, Atom bomb, nuclear reactions, A-bombs, Fusion weapons, thermonuclear weapons, hydrogen bombs, H-bombs

Id: jqLbcNpeBaw

Length: 136min 19sec (8179 seconds)

Published: Mon Nov 20 2017