Nuclear Bombs for Dummies
I was probably ten years old at the time. It was 1989 and the cold war was coming to an end but still wasn’t quite over. The Berlin wall had fallen and Mikhail Gorbachev was making ground breaking policies that would pave the way for a resolution between two nuclear superpower nations. I was an academically average 4th grader who enjoyed typical hobbies like nose picking, bike riding and obsessing over nuclear bomb design.
I didn’t really understand what the cold war was and Mikhail Gorbachev was just some guy that I knew from comical caricatures that exaggerated the weird and funny birthmark on his forehead. I was focused. I didn’t care about cooties or grades or the looming nuclear apocalypse, I only cared about atoms and how they split.
When science project time came around, my project was simply called “How Nuclear Bombs Work”. It was an arrogant title that implied that I had some clue about how one of the most heavily guarded secrets at the time was achieved. My theory was that there was a coiled particle accelerator(I used a picture of a copper coil condenser) that would spin atoms fast enough that they would fall apart and begin to collide with one another creating the dramatic mushroom cloud outcome made famous by the ‘duck and cover’ video series and the propagandized images that overwhelmed our TV’s and newspapers.
I was totally wrong, of course. But my teacher didn’t know that, no one except for a select group of scientists at the time really knew. When my teacher finally made her way around the class to my project, I stood proudly by my assembly of magazine clippings, glue and poster board. I looked right at her and announced my project title, I was sure that I would make her so proud of my burning desire for science and theoretical prowess. She was not. She went totally berserk. She snatched my project up and quickly rolled it into a top secret bundle of documents bound for the incinerator. She looked around to make sure that I hadn’t infected the other children with my blasphemic and treasonous science-smut. She told me that I had no idea what I was doing and I’ll never forget the way I felt when she angrily muttered “never do that again”.
She may have stunted my interest in education, but she did not snuff out the radioactive inferno expanding in my mind.
So, if you’d like to know how nuclear bombs work and you’re not sensitive to cuss words, please indulge me while I go on about one of my favorite subjects.
In the interest of being thorough, lets start with atoms, (in hipster voice)you’ve probably never heard of them...
Atoms: A brief reminder for jocks and other people who didn’t pay attention in school, forgot or just don’t care.
These little fuckers known as atoms are made of protons, neutrons and electrons. We don’t need to focus on electrons because they’re more important in chemical reactions and we’re interested in the nucleus because that’s where NUCLEar reactions happen, so just forget about those worthless little electron dick-sparklers.
Back to the ‘cool’ parts of atoms: protons are positively charged particles and neutrons are neutral, they have no charge. Think of neutrons as little rocks in the nucleus of an atom and these even smaller fuckers called quarks(most commonly ‘up’ and ‘down’) inside of them are what bind them to protons with what’s known as the ‘strong’ nuclear force. The weak nuclear force is responsible for radioactive decay and more pertinent to this topic so just quit it with your internal dialogue about how the strong force is better than the weak one.
Atoms are defined by the amount of protons(the atomic number) they contain, and atoms of the same atomic number with varying amounts of neutrons are referred to as isotopes. Your mom however, is defined by the amount of cellulitrons contained in her lower thigh flaps.
Uranium: This is mostly why terrorists, Aborigines and Chipmunks don’t have Nukes.
You’d think that Uranium is rare stuff but it’s really not, it’s actually more abundant than mercury and silver. If you cared to remember the whole isotopes speech I gave, then Uranium has 3 isotopes, 2 of which we’re interested in; U235 and U238. U238 has 3 more neutrons than U235 and there for is heavier and a fertile isotope. U235 is the stuff we’re really interested in. Out of all the Uranium that comes out of the ground, only 0.7% is U235 and 99.3% is U238.
Getting enough U235 to make a baseball sized sphere or ‘enriching’ U235 is very tricky, expensive and takes an enormous amount of human and industrial resources. Basically, during the Manhattan project we built a factory floor larger than the entire automotive industry full of specially designed centrifuges that separate Uranium isotopes based on their slight(3 neutrons) weight difference to make the 60kg of 80% enriched U235 that was used in the Hiroshima bomb.
That should give you some scope of how hard it is to enrich this glowy goodness. In modern times, 0.7-20% U235 is considered ‘low enriched’, 20% or more is considered ‘highly enriched’ while the US and International standards for weapons grade Uranium is 93% and 90% U235 respectively. If the weapons grade Uranium is 90% U235, the other 10% is U238 and that U238 is also called depleted Uranium because it has been depleted in the enrichment process. U238 is still really useful stuff because it’s hard as hell and still radioactive.
Plutonium or P239 is a man made element and an even better material for making bombs as it is 3X more reactive than U235. Plutonium is usually made in what are called breeder reactors. Breeder reactors use U235 for generating power and also contain U238 which can be turned into U239 once it captures a neutron. Remember when I said that U238 is a ‘fertile’ isotope? Yeah, I’m sure you do… Well, yes, it is. U238 is more likely to capture a neutron than it is to get split by one, which is also one of the reasons that U235 is a better isotope for bombs. So, U238 captures a neutron and becomes U239 for a moment and then beta decays into P239 or Plutonium. Blahblahblah, by the power of Greyskull humans make Plutonium and it was named after Pluto, which isn’t even a planet any more, so there, I could have just said that I guess…
Fission: Not the kind that you do drunk at the lake.
Fission is all about neutrons. You need to get neutrons to travel at the right(slow) speed to slam into other atoms and split them apart. I could go on and on about this so I’m gonna try to make this as fast and painless as possible.
You want fission to be planned and controllable. Spontaneous fission is not planned and is spontaneous. Spontaneous fission happens when you’re a dumb ass and didn’t handle extremely dangerous materials properly. Spontaneous fission is bad.
To controllably jumpstart fission, most bombs use a neutron generator. A neutron generator is a device made with Beryllium9 and Polonium210 and guess what? It generates neutrons. It generates neutrons that travel at the right slow speed to intercept with your fissionable atoms. When I say slow, I’m using it lightly but mostly relatively because while slow neutrons still move really fucking fast, they are slower than fast neutrons.
Let’s say that you’re fissioning some U235. You shoot some neutrons at it and hit one U235 atom and split it. When that atom violently splits in two, it releases kinetic energy and radiation(alpha, beta, gamma, x-ray and basically ‘fallout’), that energy is what creates boom for bombs and heat for power plants. ALSO, the split U235 atom releases 2–3 neutrons that shoot off and collide with other U235 atoms and precipitates a chain reaction. This is fission, and depending on the rate at which a certain amount(millions, billions or billions of billions) of atoms are fissioning; you get hot steamy power rods or great balls of fire.
Fission is also about containment. You want to densely trap atoms together in a way that will promote neutrons hitting other atoms. Power plants use rods because the shape of the rod allows a certain amount of neutrons to escape so the fission can be more easily controlled. Neutrons are also ‘moderated’ by water in most power plants to make sure that they move at a controllable rate. Bombs use spherical ‘pits’ of fissile material because spheres have less surface area and that creates the best environment for contained neutron bombardment chain reactions or fission.
A critical mass is “the minimum amount of fissile material needed to maintain a nuclear chain reaction”-The Googles
There are of course different levels of how critical a mass is. A sub-critical mass is when there’s not enough neutrons or too many neutrons escaping to sustain fission on it’s own. A critical mass is when the mass can sustain fission without any assistance and a super critical mass is SOOOPER! Like your gay friend’s new shoes except it can destroy entire cities and worlds.
Got it? Now we can move on to the really fun stuff!
Bomb Design: Yo dawg! Dats a bomb design yo…
The first nuclear bomb ever tested was called ‘Trinity’ and it was obviously named after the super hacker hottie from “The Matrix”. It was an implosion style bomb, which is the ONLY known bomb design worth a damn.
The other bomb design is called a ‘gun style’ bomb and it’s as stupid and juvenile as you’d think it is. The gun style bomb may have well been created by Fred Flintstone’s boss because it uses conventional explosive to fire a critical mass(shaped like rings) of Uranium onto another critical mass of Uranium inside of a giant gun barrel. This design was what was used for the Hiroshima bomb and it was never tested because it was so ridiculously brutish that it had to work. It also used 60kgs of 80% enriched Uranium, so it was big, dumb and inefficient.
The bomb that was dropped on Nagasaki was an elegant implosion style bomb that used a mere 6kg of Plutonium(P239 is 3X more reactive than U235). Like I said before, Plutonium is a superior bomb material because of it’s increased reactivity. One of it’s superpowers is that it can capture a neutron and become Plutonium 240 which gives it a ‘God Mode’ fission rate and creates more heat emission and radiation than U235.
An implosion style bomb implodes. Yup, that’s it. That’s all you get. Done.Bye.
J/K
Early implosion bombs were solid P239 pits with a neutron generator surrounded by a tamper of U238 and encased in conventional explosives with perfectly positioned reflectors and krytron detonators. The idea is simple and INCREDIBLY hard to do; jumpstart fission into a critical mass with a neutron generator and then trigger perfectly timed blasts that put an extreme amount of perfectly even inward pressure on the pit until all of the atoms are so close together and trapped in that it fissions at a super critical rate and explodes.
So, you’re probably like; tamper? Krytron? Refelctors? WTF Chris?
I’d like to now talk a bit about tampers, they are very important. A tamper is a dual purpose shell that goes around the pit of the bomb. Most tampers are made from U238 because it is a very hard material and therefor is known to reflect neutrons. Even though it’s a fertile isotope that likes to trap neutrons rather than split, it can still split and add to the bombs explosive yield.
A tamper does two very important things. The first thing it does is act as a neutron reflector; that means that instead of escaping, most of the neutrons bounce off of it and back into the pit to maximize fission. The second thing it does is hold the pit together for a bit longer. How long is a bit you ask? I’m glad you asked. This particular bit can be measure in ‘shakes’. A ‘shake’ is a term that some lab nerds came up with to represent a 10 billionth of a second, or the time it takes for one fission. So, as the pit fissions like mad crazy, it’s also becoming gaseous and expanding rapidly. The more the pit expands, the less density you have for splitting atoms. The tamper holds the pit together for just a few ‘shakes’ which is long enough to greatly maximize the efficiency and yield of the bomb.
Reflectors are simple, they reflect conventional explosive blasts to create the even pressure necessary for implosion. Krytrons are devices capable of delivering electrical currents for detonation with extremely precise timing.
Now that we’re slightly versed on how implosion bombs work, let’s talk about some improvements that were made on the design.
The first improvement was to hollow the pit. Having a hollow pit made the bomb safer because with space in the middle, there was less of a chance of neutrons starting any unwanted fissioning. More importantly though, it made the pit easier for the explosives to crush since it wasn’t a hard solid mass.
The next improvement was to levitate the pit. By creating a gap of air(space) between the outer part of the tamper and the explosives, the explosive’s effect was increased. The example that I heard was; “if you wanted to hammer a nail in, it would be hard if the hammer was attached to the nail.” The space that the hammer travels through the air increases it’s force and the same principal works for the levitated pit.
The next improvement is a real doozy.
Since implosion weapons now had hollow pits, I’m sure some genius was like; “Hey, we should put something in there and make this thing even more horrific”!
And they did…
Back at the Legion of Doom…
Trigger happy desk-jockey’s figured out that if they insert a small tube into the hollow pit, they can inject Tritium into it! Why is that cool/important? Tritium is basically like Hydrogen on steroids and if they could add that to the fission bomb then it would be boosted by fusion and with that; The Hydrogen bomb(or boosted fission bombs) were born.
Now, I’m sure you already know this but I’m gonna say it anyway. That big yellow thing in the sky that we call the sun is a giant fusion generator. One day God farted and that fart caught on fire and started burning at millions of degrees and with that extreme heat and pressure it started to sustain itself by fusing the most abundantly known element in the Universe(hydrogen) into Helium. When the sun fuses two Hydrogen atoms together, they become a Helium atom and that Helium atom is not quite equal to the sum of the two Hydrogen atoms. The ‘not quite equal’ part that doesn’t go into the Helium atom is energy in the form of heat and radiation.
Fusion is awesome because it does not create unwanted radiation(fallout) like fission does. The only problem is that the only way us piddly humans can create enough heat and pressure to fuse atoms is with fission.
It’s actually strangely complicated, see the fission creates fusion and the fusion adds to the fission. Remember when I said that it’s all about the Neutron-jamins? Boosted fission weapons are a fission/fusion/fission reaction, because the more heat, pressure and neutrons the merrier! Fission bombs alone are not very efficient because they rely on a chain reaction that can only be controlled to a certain extent. If you add some fusion action into the equation, more of the fissionable material can be used for yield.
You’ve probably heard the word ‘Thermonuclear’ before. Right? Thermonuclear weapons are two stage weapons.
It’s simple once you get the hang of boosted fission weapons, infact, a boosted fission bomb is the first or primary stage! See, you’ve already got the first stage down! Good for you. The secondary stage is easy too; it’s MORE FUSION! Look at you, you got this.
The second stage consists of a pit of U235 surrounded by Lithium Deuteride(a stable Hydrogen rich solid), surrounded by a tamper of U235 or U238 and both stages of the weapon are encased in a special foam that helps keep those two love birds together. The sheer obnoxious amount of fissionable materials in this design makes it super deluxe as far as it’s potential for yield. The primary(boosted fission weapon) goes off first and crushes the secondary, triggering fusion with immense heat and most importantly radiation pressure.
Are you ready for this?
Since the fission makes the fusion possible and the fusion helps maximize the fission. This means that Thermonuclear weapons are fission/fusion/fission/fusion/fission weapons(literally, in that order), haha.
Of course, none of this is as stupidly simple as I make it sound. EVERYTHING; mining, enriching, designing(especially implosion systems), manufacturing and assembling takes an astonishing amount of super smart know-it-alls, money, resources and manpower. If it was simple, then North Korea would have nukes… Wait, uhm… Shit…
There are endless amounts of details that I have omitted and that I just don’t know, but I am always on the lookout for new information to tantalize my brain-taint.
I’m not sure if my 4th grade teacher discouraged me or made me into the knowledge hungry savage that I am today. I know one thing though; I swear on the continent shaped mark on Gorbachev’s head that I will never stop searching for answers, I will never stop learning and I will never stop until…
