How do Nuclear Bombs Work? - Real Chemistry

Also check out the next video in the series on how hydrogen bombs work:

[PaperWill]

How the hell is this floating at 2k views? It’s an absolutely perfect explanation.

[parthchaturvedi]

Thanks, it helped me win a reddit arguement.

[mortenknudsen]

This is so well made and explained, Thank you. My brain itch is finally gone :P

[bassfischer]

BY FAR the finest explanation of the fission dynamics of Uranium and Plutonium atomic bombs that I've ever seen. Thank you!

[ChimpFromSpace]

Just the explosive lens itself is an insane feat of engineering. Using geometry, and chemicals with different combustion speeds to turn outwardly expanding explosions into an inwardly collapsing implosion. Even mechanics of the neutron source at the center of the imploding core is also fascinating, and genius. For better or for worse, the people who worked on the original Manhattan Project were very very smart, to say the least.

[markotrieste]

Conventional PWR reactors run on about 5% enriched uranium. 20% enrichment is considered "high assay low enriched uranium" and is used in smaller naval reactors.

[christoskokkolis]

Fantastic video and very clear explanation, thank you!

[ethanbautista]

Thank you so much it really helped me on my project.

[drtidrow]

To clarify: a critical mass is when each fission causes one additional fission so the fission reactions stay at a stable rate (what happens inside a nuclear reactor), a subcritical mass produces less than one additional fission per fission event thus the reaction dying off, and a supercritical mass has more than one additional fission per fission event, so the reaction rate keeps growing. Nuclear bombs, when they detonate, create a highly supercritical mass so that the reaction rate accelerates extremely rapidly and fissions a large fraction of the uranium or plutonium present.

[ihaveaboyfriendmeh]

Wonderful exposition.
Quick question. What are the favorable weight of the critical mass in terms of density and weight in kilograms?

[davidgrisez]

This is an interesting description of the Teller-Ulam design for a thermonuclear bomb. At least public information indicates that this is a likely possibility for the thermonuclear bomb. Us human beings are really great at making tremendously destructive devices.

[drtidrow]

8:30 Another clarification: Most plutonium 239 is created in nuclear reactors, where there are lots of neutrons flying around. Some of the Pu-239 formed will absorb an additional neutron forming Pu-240. This isotope of plutonium has a very high spontaneous fission rate, which means there are always extra neutrons flying around inside a chunk of Pu-239. As a result, you have to bring the subcritical pieces of a bomb core together very fast into supercritical mass before those neutrons can get the chain reaction going and blow things apart. This turns out to be much faster than a gun-type design can produce, so they had to switch to implosion. As a bonus, implosion creates a much denser supercritical mass and thus allows much more of the plutonium present to fission.

IIRC, Pu-239 also has a higher spontaneous fission rate than U-235, which didn't help. This made the gun-type plutonium bomb design almost impractically long to begin with, then they discovered the problem with Pu-240's fission rate, which made it impossible to make a gun-type bomb of any reasonable size. You can find pics online of prototype "Thin Man" plutonium bomb casings that they made before the spontaneous fission problem nixed the whole design. They're roughly twice as long as the Little Boy uranium bomb, and that still wasn't long enough to work.

[davidnaugler]

The Born-Oppenheimer approximation is central to understand how Nuclear Bombs Work. BO says nuclei move at least 1/2000 times the speed of electrons. Hence nuclear fusion begins when the electron temperature is high enough to activate D-D or D-T fusion.

[Mr.Nefarioussness]

Im drunk asf & I understood this perfectly wtff lol I feel like I just unlocked a new knowledge😂

[Sokol]

Latter the explosive lens was simplified in a tubular explosive charge, using a solid oblate spheroid Plutonium pit, and thus achieving the same symmetric compression, but this arrange allow make smaller - in size; bombs, and so put 10 thermonuclear warheads in one ICBM.

[nickelbrille]

Ok, but where does the first neutron come from that starts the chain reaction. Is there something like spontaneous nuclear fission in uranium/plutonium that releases neutrons ?

[richardhenry]

Iron ore? Gaseous diffusion? Po-Be Neutron initiators?

[MINIbrickz]

im year 9 and doing this sometimes i question myself

[qinglinchen]

on the left you see little boy, on the right you see fat boy. luv that quote

[hanjoyitsu]

i totally wouldnt be here if it wasnt for my curiosity of whats happening right now...