Going Nuclear – The Science Of Nuclear Weapons – Part 2 – Chain Reactions

Click any button for sharing!

With the basic theory having shown that a nuclear chain reaction was possible the next step is to actually make it work, first with a stable nuclear reactor – the Chicago Pile 1. Then we discuss how to go from a controllable reactor to the very first nuclear device – the Little Boy.

  1. Sir Commenter

    5:28 I don’t think that’s how the laws of physics work.

  2. Daniel Lassander

    More please i love this sort of information!

  3. VicariousReality7

    8:00   What is the reason for using carbide then? That is significantly less dense than pure tungsten?

  4. Julian Turner

    No ads, is the channel ok?!

  5. R Nacnud

    For all us non intelligent lifeforms the secret is to bang the rocks together.

  6. Ben Quinney

    The universe is perverse

  7. #1 Tako

    Darn… I was hoping that Cody’s Lab would be returning the favor you gave him 8 months ago.

  8. Halmai Balazs

    Love this series!

  9. Wiktor Guzowski

    Could You list sources in the description?

  10. Ant

    And now Scott is on a watchlist

  11. Paublus Americanus AMERICANUS

    scott: when looking for the nuclear initiator, look for urchin. You will find it is beryllium 9, and polonium 210. These items for the trinity blast and hiroshima and nagasaki might have been difficult to obtain, but they did have a reactor at hanford, from which to aggregate the necessary amounts of these man made items. When you are getting plutonium in the 5 kilo-gram amount completely made by man, these other components in the amount necessary will be pretty easy to obtain. The urchin may have been diff in the first units, something with good production and a neutron emitter. Labs may have had this before trinity. I read many years ago it was a different element which I am reluctant to state here.

  12. Peter Hamilton

    Have there every been any cases of a device exploding from pre-detonation during assembly?

  13. Bill Davis

    10% chance of self destination… what?

  14. Edu

    It was newborn and 10 feet tall,
    But they called it Little Boy,
    And C7, H5, O6, N3, they call him

  15. PerfumedManatee

    They used a hollow plug for Little Boy… damnit!

  16. Jackie Singleton

    IDK why the explanation at 5:22 made me laugh… but it did. P

  17. M12Howitzer

    Another very interesting science video! Keep it up and thank you!

  18. matsv201

    2:20 “Adjust the neutron absorption rate, this is done by control rods”
    No. That is not really accurate. The Neutron absorption rate is controlled by the moderators, not the control rods. The control rods are used to control the power of the reactor and are mostly all the way out in a modern reactor.
    The problem with controlling the absorption with rods are two. 1: it burns the fuel uneven. 2: it may make the reactor instabile and be overcritical. This is for reactors that got negative gain void coefficient. That is, if there becomes a void in the coolant (say water), the reactor speeds up in steed of slow down. This was the issue in Tjernobyl and the reason why the reactor blow. It was pretty much a combination of several different factors. The sad part is that this was well known years before even the reactor was planed.
    Again, this is never the case with modern nuclear reactor. Simply having a moderator that change characteristic with temperature they the reactor can go over critical and sub critical in matter of milliseconds. Actually different part of it can be over critical and different part can be sub critical at the same time. The advantage of this being that the reactor can never become highly over critical or super critical, because then the moderator will just boil of and stop moderating.
    In other reactors like NaK, Lead and Salt they use other physical changes in the moderator to make the reactor over or under critical, removing the need for the moderator to boil.
    Also say that Putting Natural uralium in normal water it will never become critical. U235 have to be concentrated to around 1.5% or so (from 0,7%) to be critical. So early reactors used heavy water or graffite. (that was what the heavy water plant in Norway was for during WWII).
    By the 50-tys the technology of concentrated U235 become cheaper light water reactors was more economical. First one used around 2% just to be “safe” but fairly early one with light water reactor one recognized that can use much higher amount of U235 because of the void coefficient pretty much making it impossible for a light water reactor to become over critical. Civilian reactors there for start using 3-3.5% fuel so they could burn the fuel for longer before it dropped under ~2% (well really a bit lower because of the plutonium that is created).
    One relized then that having a higher concentration of U235 actually make the reactor more controllable, not less. Also making it be able to have more power in a denser structure and work for a longer period of time. Submarine reactors for example have about 20% U235.
    Some old reactors also have been uppgradera to higher power. This have been partially done with making a more efficient turbine, but also by replacing the fuel rods with one with one with more U235. Now days about 4.5-5%. A 4.5% concentrated fuel rod also produce 50% less radioactive waste than 3% once… actually its even a bit bigger diffrance than so because of the reactor be able to burn more of the plutonium as well.

  19. Ruellibilly

    Fun fact: Only 2% of the uranium of little boy actually underwent nuclear fission.

  20. Megalodawn

    Hello NSA! Come for me!

  21. olivier0092

    Hi Scott. I’ve asked Amy from Vintage Space to do a video on the Ekranoplan. But perhaps you could do a physics explanation? That would be awesome!

  22. Dai1989

    I know this got demonetized, but this is an amazing series and would love to see more!!!

  23. Harry

    How were the workers who assembled little boy and worked on reactors shielded from radiation?

  24. Prof2You Smithe

    I am following your series with a great deal of anticipation for the next! Thank you for pointing out the errors in the Little Boy schematics. Always drives me crazy lol!
    Have you thought of a discussion on the Krytrons or the PAL’s? I find that technology fascinating.
    Keep up the great work!

  25. Adam Harvey

    Can’t wait to see what you’ve dug up on Gadget and the like!

  26. Stephen Kneller

    Abner was most likely a simplified version of the Urchin initiator in the implosion type weapons.
    “ Initiation
    Once insertion is completed, neutrons need to be introduced to begin the chain reaction. One route to doing this is to use a highly reliable “modulated” neutron initiator, an initiator that releases neutrons only when triggered. The sophisticated neutron pulse tubes used in modern weapons are one possibility. The Manhattan Project developed a simple beryllium/polonium 210 initiator named “Abner” that brought the two materials together when struck by the projectile.”
    “ Modulated Beryllium/Polonium Initiators
    ….The Urchin was a sphere consisting of a hollow beryllium shell, with a solid spherical beryllium pellet nested inside. The polonium was deposited in layer between the shell and the pellet. Both the shell and the pellet were coated with a thin metal film to prevent the polonium (or its alpha particles) from reaching the beryllium. The mixing was brought about by using the Munroe Effect (also called the shaped charge, or hollow charge, effect): shock waves collide, powerful high velocity jets are formed. This effect was created by cutting parallel wedge-shaped groves in the inner surface of the shell. When the implosion shock collapsed these grooves, sheet-like beryllium jets would erupt through the polonium layer, and cause violent turbulence that would quickly mix the polonium and beryllium together.
    By placing the small mass of polonium as a layer trapped between two relatively large masses of beryllium, the Urchin designers were hedging their bets. Even if the Monroe effect did not work as advertised, any mixing process or turbulence present would likely disrupt the carefully isolated polonium layer and cause it to mix.
    The whole initiator weighed about 7 grams. The outer shell was 2 cm wide and 0.6 cm thick, the solid inner sphere was 0.8 cm wide. 15 parallel wedge-shaped grooves, each 2.09 mm deep, were cut into the inner surface of the shell. Both the shell and the inner pellet were formed by hot pressing in a nickel carbonyl atmosphere, which deposited a nickel layer on the surfaces. The surfaces of the shell and central sphere were also coated with 0.1 mm of gold. Combined with the nickel layer, the gold film provided a barrier between the polonium and the beryllium.
    50 curies polonium-210 (11 mg) was deposited on the grooves inside the shell and on the central sphere. This much polonium produces a thermal output of 0.1 watts, causing very noticeable warming in such a small object. Post war studies showed that no more than 10 curies still provided an acceptable initiation effect, allowing the manufacture of initiators that remained usable for up to a year.”

  27. Casey28xxx

    I’m expecting some North Koreans to start subbing…to educate their new nuke scientists on atomics 101 or so they can see where they may be able to improve their designs.

  28. NightLurk

    Are you also a free climber? Cause your cliff hangings are notorious…

  29. Jett Quasar

    I know where this is going… Project Orion!

  30. Harrison Erbe

    The star of this reminded me of donnie darko

  31. criticalfxck13

    9 dislikes
    That is one bitter cat

  32. The Virtual Scotsman

    Love this series

  33. Ben D

    Very interesting scott, as per usual! looking forward to the next episode(s)!

  34. Sean McNamara

    Aw yiss, my favorite series right now :D So interesting!!!

  35. Richard Dastardly

    This is a good level of explanation, I like it. You’re sounding more scottish than usual today for some reason…

  36. Jamie

    Thank you Scott for this video series. It’s especially interesting for me as later today I take the test to qualify for the Navy’s nuclear program.

  37. William Warren

    Thank you. This is extremely good.

  38. Grzegorz Kapica

    Man, I hope they don’t take your channel down for this. Great informative video. Thank you Scott.

  39. Jack Meadows

    So when are we getting to the how-to tutorial part? I got all my weapons grade uranium in the living room

  40. Brady B

    I think I’m really going to enjoy this series :) I’ve been really interested in nuclear energy the last couple years, and if I ever went back for a Masters degree, it’d be in nuclear engineering. Thanks!

  41. MrSaliVader

    Can’t wait for the third part!

  42. Starlight Crusader

    I’M WILD

  43. Vampyricon

    Thanks for the video! If you’re going to cover nuclear stuff besides weapons, can I request a video about liquid thorium fluoride reactors?

  44. Jason Sharkey

    Do fusion!

  45. Joanna Hammond

    To be honest, I can’t see why you’ve been demonitised as all this information is out there and easy to get hold of if anyone is seriously interested in finding out. Building a basic nuclear device would not be that hard, getting hold of the materials to do so would be.

  46. DEEDEE-101

    Scott this is currently my most favorite ongoing youtube series in existence. Please just continue down this route and bring us many episodes and Spin-offs.

  47. Pennpenn

    So I’m guessing the Demon Core is next episode? (Or maybe 4)

  48. thedreadnote

    Loving this series, so fascinating!

  49. NoName

    Heroshima had a 10% chance of becoming a radioactive abounded city from Heinlein’s book?

  50. Tomas T

    nuclear reactor is basically a controlled A bomb :D

  51. zubmit

    Very interesting. Can’t wait for the next part!

  52. Richard Cranium

    Hey Scott. Could you make a video about fusion and the materials that might be used in achieving sustainable fusion.

  53. Matt Harding

    Really interesting subject, I don’t think anyone watching can make a viable device simply because of how hard it is to make to obtain U235.

  54. Garry Mcgrath

    Neutron generator is not necessary in a gun bomb, but would give a better yield,

  55. mohamed zh

    Will you consider making videos about fusion reaction ?! it is a hot topic as a new source of energy !

  56. Great American

    Love the syzygy coke bottle in the background.

  57. Mads Borlund

    Thank you! This is the first good explanation of a “prompt critical” reactor I have come across.

  58. fortyfukinseven

    I’ve always been fascinated by nuclear reactions, but due to the stigma, I’m hesitant to do much research. I appreciate you walking through it in a more educational, and historical manner.

  59. Bobby Vincent

    this is a great series here – thank you

  60. Trey Mixon

    Needs more shirt

  61. Peter Jerde

    I love descriptions of “instantaneous reactions” like nuclear detonations slowed down and discussed microsecond by microsecond!

  62. The Siren

    Great video love to learn about the Evolution of the atomic bomb…

  63. Sander Cohen

    When on the eve of the Chernobyl disaster, it was officially announced to the people of Pripyat that there would be a “temporary” evacuation…
    The message was as follows, roughly translated to English: “Attention, comrades… An unsatisfactory radioactive situation has occurred at the Chernobyl power station. As a temporary precaution, it has been decided to evacuate people from the neighbourhood of Pripyat from 2 PM today 27th April.”
    But don’t worry, it’s only “temporary”… ;)

  64. Didddin duuu nufffin Wakanda enn shiiieet

    Tungsten has near the same density as gold.

  65. Renzsu

    Thanks for this great tutorial! Fun weekend project :)

  66. Oliver Turner

    Woohoo! loving this series so far.

  67. Max MusterSpace

    I really enjoy this series. Thank you! =)

  68. warren heyman

    Thank you DR. Manley. Great series

  69. IstasPumaNevada

    Always leave ’em wanting more. :)
    Quite enjoying these videos.

  70. Table Salt

    “There is a moment” – Dr. Mann

  71. DETHdressedInRED

    Mister Scott, I freaking love your videos. MAN I LOVE SCIENCE!

  72. Sebastian Finke

    Very interesting. I can’t for part 3. Thanks Scott.

  73. Joseph Godfrey

    Seems like “Abner” might still be of a classified design.

  74. tanks608

    I just wanted to say that this is one of the most interesting series I have ever watched. It is really fascinating to hear a more than rudimentary explanation of nuclear history and theory that is clearly and effectively presented. Thank you so much and great job scott.

  75. Reckless Roges

    7:46 Isn’t it the *inertia* rather than the momentum, that keeps the two masses together?

  76. Micah van Everdingen

    Fbi: Are you going to use this knowledge?

  77. Eto Hige Gamer Culture

    pretty cool background info for when I’m playing Factorio and building a reactor and painstakingly have to make 235 b/c 238 is garbo lol

  78. Ville Turpeinen

    Thanks for the upload, can’t wait for the third episode! I find this series so I interesting that the whole video felt only one minute long.

  79. Evan Larson

    *loud nsa coughing*

  80. Dominik Goslawski

    right that’s all i need to know, now were is my tool box

  81. Elminator666

    My stepfather was involved with these weapons, I believe from the Manhattan Project until his retirement in 1990 I believe. I don’t think he’s particularly well known, but he is the editor of the Handbook of Nuclear Weapon Effects.

  82. Jack Hutchison

    FBI is going to be all over you now…

  83. HisRoyalCarlness

    Also important note. When you were talking about explosive consequences for not moderating the reaction correctly, that’s more often water flash boiling or hydrogen buildup/detonation. While the energy multiplies very fast, it’s still not weapons grade Uranium, as you said. Thus meltdown literally means melt-down.

  84. Niels Daemen

    Wow, this video has the higgest like to dislik ratio i have ever seen! 798/0 Wtf?

  85. Runic Sigil

    Thanks for telling us how to make nukes. I appreciate the tutorial. Marshal Kim will be very pleased.
    ( ͡͡ ° ͜ ʖ ͡ °)

  86. Christopher Willis

    Fun fact, the gun style bomb was supper inefficient, consuming less than 2% of the fissile materials! A small contingent of folks thought this so wasteful as to consider not using this style of bomb, but of course, they lost that argument.

  87. Ironhead

    Of course this goes live while I’m playing Fallout 4. lol

  88. BryanFDNY

    Will you be talking about Fusion devices ? I find those personal very intriguing, the risk they took during their development and nonchalance with witch they conducted the tests are absolutely mind boggling

  89. gascan

    Will you be going into power reactor designs as well as bomb designs? I’d love to hear some discussions of the various designs currently in use (pressurized water reactors, boiling water reactors) proposed designs (thorium, fusion, etc)

  90. Michael Jordan

    Part3: practical bomb construction

  91. Baron von Quiply

    I love it! The only channel on YouTube to teach you how to build a rocket, launch it, and make sure there’s a nuke onboa-…
    I’ve just been told I’m now on a list ='(

  92. PiezPiedPy

    NSA are now giving away Free NSA T-Shirts for all those new to the list

  93. Theophrastus Bombastus

    Dude, I hope this is a 50 parts series.

  94. Oskar Wallin

    Woop! You should really consider starting a educational channel! Love listening to your videos like these

  95. enthalpy

    Side note: when we start up a commercial power reactor, we go slightly supercritical. For a commercial reactor we have a multiplication factor that gives us about a 15-20 minute doubling time. Very slow but also very safe and controllable. There are either reactor period trips or flux range trips to prevent a runaway and automatically shut down the reactor.

  96. DominantReverse

    I swear Kim is watching this with me

  97. Joel Wojkiewicz

    “Supercritical Mass Of Fissile Material” Well, found my new bands name.

  98. Dr Swam

    YouTube demonetises first video, uploads second anyway :D

  99. enthalpy

    Nuclear engineer and licensed senior reactor operator here. I operate a boiling water reactor. Thanks for helping to spread some education about nuclear power!

  100. Ty Rogers

    Wow Scott, I can’t believe your posting this anti advertiser friendly content again ;) (YouTube is ridiculous)

Comments are closed.