Nuclear Fission Visually Explained

Atomic Bombs and Nuclear Reactors Simulated. Explaining why critical mass is a confusing term in nuclear physics. The critical mass depends on a lot more than the mass in nuclear fission. Using simulations to show these reasons as well as how a nuclear reactor are designed, and how an atomic devices work.

The critical mass depends on:
Mass, Purity, Geometry, Density, Neutron Initiator, Tamper, Neutron Deflector and more

Critical Assembly Simulator by Alex Wellerstein:

0:00 Introduction
0:40 Nuclear Fission & Critical Mass
2:58 Building the simulation
5:06 Criticality: Purity
6:11 Criticality: Control Rods
7:22 Criticality: Shape
8:20 Criticality: Density
10:05 Criticality: Neutron initiator
10:28 Criticality: Tamper
10:54 Criticality: Neutron reflector
11:24 Thanks for watching

[jkzero]

Nice simulations, but why did you use graphite for the neutron reflector? Graphite is a great neutron moderator, but that is the last thing you want to do to neutrons in a bomb. Little boy used tungsten carbide and the Gadget used depleted uranium. FYI, I have all the calculations solving the neutron diffusion equation to determine the critical mass on my channel.

[Etrehumain]

Oh that's why when Vsauce talk about hiroshima he said that most of the fissible material was blown away and only 1% or something reacted. It's because it was not dense enough, pressurized by compressing explosions on all side to contain the fissible material. I get it now.

[savagemuir]

Fantastic video! Also the tamper is forced inwards by the compression explosion, so it provides more compressive kinetic energy to keep the core together for a bit longer.

[anantakabir]

Comes back with an absolutely amazing video. Love your content

[zapphysics]

Absolutely phenomenal video!! Great to see you back!

[enekuda]

Man such an under-subscribed channel! Amazing videos!!

[VojtaTravnik-cjxo]

thanks helped me a lot, now i know why it didnt work as expected

[MrGrace]

This is one of the coolest videos ive ever seen on Nuclear physics.

[moiraatkinson]

This channel has been an excellent find! I’ve become really interested in all things nuclear after watching Plainly Difficult videos, then finding Kyle Hill. A bit late as I’m already retiring age! This was another amazing simulation and a great way to explain the workings of an atomic bomb. You’ll have to do a simulation to explain the so called hydrogen bomb next 😊.

[omamba]

Small gripe: fission of U-235 doesn’t always release 3 neutrons. It’s 2 or 3 neutrons, averaging ~2.4 neutrons every fission. (I wanna say it’s 2.41 neutrons, but it’s been a long time since I’ve dealt with fission).

[ThomasHaberkorn]

1:44 Regarding the split of U235 into Kr92 and Ba141: do the fission products occupy a larger/smaller/same volume than the original U235?

[rosettastone]

Wow, what an incredibly interesting video!!!! 👍

[fichaeljmox]

This is best explanation I ever heard!

[ramadhanisme]

Thank you for your video, really enlightened me about nuclear

[AdamPeterson-owmy]

2:51 On the contrary, it would be great for bowling.

[chupacabraattack]

Now I understand how control rods work!

[TheContrarian-iisu]

What program did you use to simmulate this? Unity and C# or just pure code?

[severinopereiracarollofilh]

CONGRATULATIONS. Very good video and easy comprehensible explanation!

[jarek.fojtik]

Hello, please make a video about H-bomb. Great job!

[bronzedivision]

Your quip at 11:09 was really dumb for a scientist. Fun fact that "problem" you're alluding to was actually fixed by making those "evil" graphite tips 1.7 meters LONGER. And several RBMKs continue to operate just fine to this day in that arrangement.

This is possible because the graphite tips in an RBMK reactor are not stupid or accidental parts of the design; and in fact perform many key functions in normal operation. The material didn't get to the bottom of the control rods due to random chance or incompetence.